Objective and Background Early and accurate diagnosis of spinal infections,including spinal tuberculosis,is pivotal for effective treatment but remains challenging.This study aims to assess the diagnostic yield of met...Objective and Background Early and accurate diagnosis of spinal infections,including spinal tuberculosis,is pivotal for effective treatment but remains challenging.This study aims to assess the diagnostic yield of metagenomic next-generation sequencing(mNGS)compared with that of conventional microbiological tests(CMTs)in identifying pathogens associated with spinal pathologies,with a special focus on infections leading to surgical interventions.Methods We enrolled 85 patients who underwent spinal surgery,comprising 63 patients with clinically diagnosed spinal infections,including patients with spinal tuberculosis,and 22 patients with noninfectious spinal conditions.The procedures involved irrigation and debridement for persistent wound drainage,with subsequent DNA extraction from plasma and joint fluid for mNGS and CMT analysis.Results Significantly increased C-reactive protein(CRP)levels were observed in patients with infections.The mNGS approach showed greater diagnostic sensitivity(92.06%)for detecting pathogens,including Mycobacterium tuberculosis,than did CMTs(36.51%).Despite its low specificity,mNGS had considerable negative predictive value(70.59%),underscoring its utility in ruling out infections.Conclusions The mNGS offers superior sensitivity over CMTs in the diagnosis of a variety of spinal infections,notably spinal tuberculosis.This study highlights the potential of mNGS in enhancing the diagnosis of complex spinal infections,thereby informing targeted treatment strategies.展开更多
A total of fifty (50) samples of water from Lake Fitri (Chad), with 25 samples per island (Domoro and Maguite). The aim of this study was to analyze the bacteriological, biochemical and physico-chemical quality of the...A total of fifty (50) samples of water from Lake Fitri (Chad), with 25 samples per island (Domoro and Maguite). The aim of this study was to analyze the bacteriological, biochemical and physico-chemical quality of the water in Lake Fitri in Chad. Standard microbiology methods were used. Isolated strains of enterobacteria were characterized by API 20E and API Staph galleries and confirmed by API Web. Antibiotic resistance was performed according to the recommendations of the antibiogram committee (CA-SFM, 2019). Physico-chemical analysis of the water was carried out by (Rodier, 2009). The microbiological results revealed an abundance on the Domoro islands (5.37.106 ± 1.5.105 and 1.97.105 ± 4.94.104), successively for total aerobic mesophilic flora (FMAT), and thermotolerant coliform (E. coli) and on the Maguite Islands (4.71.106 ± 7.14.105 and 2.32.105 ± 2.86.104), alternately for total aerobic mesophilic flora (FMAT), and thermotolerant coliform (E. coli). The results obtained after incubation of the biochemical tests using the API 20E and API Staph galleries and their proposed numerical profile analyzed using Api software and confirmed by Api Web confirmed the contamination of the waters of Lake Fitri by pathogenic strains of E. coli, Staphylococcus and Salmonella spp. The results of the antibiogram carried out show the emergence of certain resistances to Tobramycin, Flucytosine and Teicoplanin. The average levels of BOD5, COD, SS, Nitrate (NO3) and Nitrite (NO2) for Domoro Island were 32.14 ± 2.37 mg/L, 423.86 ± 4.78 mg/L, 65.42 ± 2.27 mg/L, 0.04 ± 0.01 mg/L and 3.32 ± 1.48 mg/L respectively. The water from the islands of Lake Fitri must therefore be rigorously treated before consumption.展开更多
AIM:To determine the microbiological agents and antibiotic susceptibility of chronic dacryocystitis in recent years to guide effective treatment strategies.METHODS:A total of 308 adult patients with chronic dacryocyst...AIM:To determine the microbiological agents and antibiotic susceptibility of chronic dacryocystitis in recent years to guide effective treatment strategies.METHODS:A total of 308 adult patients with chronic dacryocystitis were enrolled from January 2020 to September 2022 in Beijing Tongren Hospital.The 229 pus specimens were taken from the conjunctival sac,while 79 specimens were taken from the opened lacrimal sac during transnasal dacryocystorhinostomy(DCR)surgery.All the samples were sent for microbiological smear and culture and drug susceptibility tests.RESULTS:The 202 specimens showed microbial growth,with a positive rate of 65.6%.The 313 strains of bacteria were isolated,including 272 aerobic or facultative anaerobes,accounting for 86.9%,and 41 anaerobic bacteria,accounting for 13.1%.The most common strains were Staphylococcus epidermidis,Corynebacterium macginleyi,and Staphylococcus aureus.Six strains of fungi were isolated.The 14 strains(18.9%)of Staphylococcus were found to be multidrug resistant.It showed a wide variety of gram-negative bacteria,up to 23 species.Specimens obtained during DCR surgery had a positive rate of 70.9%,which was higher than those obtained from the conjunctival sac(63.8%),with a statistically significant difference.More microbiological species were found in intraoperative specimens,and consisted largely of pathogenic bacteria or conditional pathogens.All the 6 strains of fungi were obtained from intraoperative specimens.All bacteria were sensitive to vancomycin,while a large number of bacteria were resistant to erythromycin.The commonly used ocular antibiotics levofloxacin,moxifloxacin and tobramycin were generally sensitive to most of the bacteria.CONCLUSION:Gram-positive cocci,gram-positive bacilli,and gram-negative bacilli are the predominant pathogens for chronic dacryocystitis.Specimens taken during DCR surgery can obtain more accurate microbiological results.展开更多
In aquaculture, feed represents the main component of production costs, and the development of this sector depends on the development of an economical feed formulation that meets the qualitative and quantitative requi...In aquaculture, feed represents the main component of production costs, and the development of this sector depends on the development of an economical feed formulation that meets the qualitative and quantitative requirements of fish. The aim of this study was to determine the nutritive and microbiological quality of fish feed formulated from local flours enriched with Hermetia illucens larvae. The raw materials used for formulation were fishmeal, corn meal, low-grade rice, soybean meal and Hermetia illucens larvae meal. Different iso-protein feed compositions were prepared with 0%, 10%, 25%, 35%, 50%, 65%, 75% and 100% incorporation of Hermetia illucens larvae meal as a substitute for fish meal. Biochemical and microbiological analyses of these flours were determined using standard methods. The results showed that incorporation of larvae meal had an influence on the biochemical characteristics ash (8.15 to 20.27%), lipid (11.55 to 24.94%), fiber (13.93 to 20.41%) and dry matter (89.65 to 91.19%) of various formulated feed. Loads of fecal Streptococci, Staphylococci, Aeromonas, yeasts and molds ranged from 2.4 to 4.9 log 10 CFU/g;3.6 to 3.9 log 10 CFU/g;2.2 to 2.7 log 10 CFU/g;2.1 to 2.3 log 10 CFU/g, respectively. The level of contamination of these flours was below the microbiological criteria applicable to animal feed. Feed formulated with 0% and 10% Hermetia illucens larvae showed the best nutritive and microbiological characteristics. These results suggest that flours enriched with Hermetia illucens larvae could be used in fish feed.展开更多
Forty-nine microbial strains were used to screen their ability for the microbiological transforma-tion of ginsenoside Rg1. Aspergillus niger (3.1858) and Absidia coerulea (3.3538) were found to convert ginsenoside Rg1...Forty-nine microbial strains were used to screen their ability for the microbiological transforma-tion of ginsenoside Rg1. Aspergillus niger (3.1858) and Absidia coerulea (3.3538) were found to convert ginsenoside Rg1 efficiently to less polar metabolites. Preparative scale transformation with both fungi Absidia coerulea (3.3538) and Aspergillus niger (3.1858) have resulted in the production of one same metabolite (MT1). Its structure was char-acterized as 6-O-b-D-glucopyranosyl-20(S)-protopanaxatriol (Ginsenoside Rh1) on the basis of its TOF-MS and 1H, 13C NMR spectral data. The biotransformation kinetic curves for Ginsenoside Rg1 and MT1 were reported for the first time, and the biotransformation pathway was proposed.展开更多
Salicylate is a type of pollutant widely and persistently existed in environ- ment. Microbiological degradation of salicylate as one kind of biological remediation methods has the advantages of low cost, good effect a...Salicylate is a type of pollutant widely and persistently existed in environ- ment. Microbiological degradation of salicylate as one kind of biological remediation methods has the advantages of low cost, good effect and no secondary pollution, and also attracts wide attention both at home and abroad. Currently, many salicy- late-degrading bacteria are isolated and screened, while the molecular mechanism of salicylate metabolism is also worth deep research. The research about molecular mechanism of microorganism degradation was overviewed, various degrading path- ways including catechol meta-cleavage pathway and gentisate pathway were intro- duced, and the latest progress in regulating genes of salicylate degradation was summarized.展开更多
Sulfate reducing bacteria(SRB) are often the culprits of microbiologically influenced corrosion(MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intens...Sulfate reducing bacteria(SRB) are often the culprits of microbiologically influenced corrosion(MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H_2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H_2S gets its H^+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H_2S is responsible for SRB MIC of carbon steel. However, in recent years,well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer(EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.展开更多
Microbiologically influenced corrosion （MIC） is a major cause of corrosion damages, facility failures, and financial losses, making MIC an important research topic. Due to complex microbiological activities and a la...Microbiologically influenced corrosion （MIC） is a major cause of corrosion damages, facility failures, and financial losses, making MIC an important research topic. Due to complex microbiological activities and a lack of deep understanding of the interactions between biofilms and metal surfaces, MIC occurrences and mechanisms are difficult to predict and interpret. Many theories and mechanisms have been pro- posed to explain MIC. In this review, the mechanisms of MIC are discussed using hioenergetics, microbial respiration types, and biofilm extracellular electron transfer （EET）. Two main MIC types, namely EET-MIC and metabolite MIC （M-ME）, are discussed. This brief review provides a state of the art insight into MIC mechanisms and it helps the diagnosis and prediction of occurrences of MIC under anaerobic conditions in the oil and gas industry.展开更多
Microbiologically influenced corrosion(MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorgani...Microbiologically influenced corrosion(MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorganisms cause severe deterioration on the metals. In this study, MIC of pure titanium(Ti) was studied in the presence of a highly corrosive aerobic marine bacterium Pseudomonas aeruginosa. The results obtained from electrochemical test showed that Ti was corrosion resistant in the abiotic culture medium after 14 d, while the increased corrosion current density(i_(corr)) obtained from polarization curves and the decreased charge transfer resistance(R_(ct)) from electrochemical impedance spectroscopy(EIS)indicated the accelerated corrosion of Ti caused by P. aeruginosa biofilm. For further confirmation of the above results, the surface of Ti was investigated using scanning electron microscopy(SEM), confocal laser scanning microscopy(CLSM) and X-ray photoelectron spectroscopy(XPS). According to the XPS results, TiO_2 was formed in both abiotic and biotic conditions, while unstable oxide Ti_2O_3 was detected in the presence of P. aeruginosa, leading to the defects in the passive film and localized corrosion. Pitting corrosion was investigated with the help of CLSM, and the largest pit depth found on Ti surface immersed in P. aeruginosa was 1.2 μm. Ti was not immune to MIC caused by P. aeruginosa.展开更多
The TiSiN-Cu nanocomposite coating was deposited on F690 steel substrate by arc ion plating. The structure and composition, tribocorrosion behavior and anti-microbiologically influenced corrosion(MIC)properties of TiS...The TiSiN-Cu nanocomposite coating was deposited on F690 steel substrate by arc ion plating. The structure and composition, tribocorrosion behavior and anti-microbiologically influenced corrosion(MIC)properties of TiSiN-Cu coating were investigated. The results show that the TiSiN-Cu coating has unique nanocomposite structures. The results of tribocorrosion show that the potential and current change of F690 steel and TiSiN-Cu coatings tend to be opposite. The reason is that the F690 steel is non-passivated metal and the TiSiN-Cu coating has passivation phenomenon. The TiSiN-Cu coating possesses excellent tribocorrosion resistance. Cu ion released from TiSiN-Cu coating can effectively inhibit the corrosion caused by SRB.展开更多
Objective:To investigate the quality of indoor air of different wards and units of Olabisi Onabanjo University Teaching Hospital, Sagamu, to ascertain their contribution to infection rate in the hospital.Methods:The m...Objective:To investigate the quality of indoor air of different wards and units of Olabisi Onabanjo University Teaching Hospital, Sagamu, to ascertain their contribution to infection rate in the hospital.Methods:The microbial quality of indoor air of nine wards/units of Olabisi Onabanjo University Teaching Hospital, Sagamu, Nigeria was conducted. Sedimentation technique using open Petri-dishes containing different culture media was employed and samplings were done twice daily, one in the morning shortly after cleaning and before influx of people/patients into the wards/units and the other in the evening when a lot of activities would have taken place in these wards. Isolates were identified according to standard methods.Results:Results showed that there was a statistically significant difference(氈2= 6.0167) in the bacteria population of the different sampling time whereas it was not so for fungi population(氈2= 0.2857). Male medical ward(MMW) and male surgical general(MSG) recorded the highest bacterial and fungal growth while the operating theatre(OT) was almost free of microbial burden. The bacteria isolates were Staphylococcus aureus, Klebsiellasp., Bacillus cereus, Bacillus subtilis, Streptococcus pyogenes andSerratia marscenceswhile the fungi isolates includedAspergillus flavus, Penicilliumsp.,Fusariumsp.,Candida albicansandAlternariasp.Staphylococcus aureuswas the predominantly isolated bacterium whilePenicilliumsp. was the most isolated fungus.Conclusions:Though most of the microbial isolates were potential and or opportunistic pathogens, there was no correlation between the isolates in this study and the surveillance report of nosocomial infection during the period of study, hence the contribution of the indoor air cannot be established. From the reduction noticed in the morning samples, stringent measures such as proper disinfection and regular cleaning, restriction of patient relatives' movement in and out of the wards/units need to be enforced so as to improve the quality of indoor air of our hospital wards/units.展开更多
The corrosion behavior of 304 stainless steel(SS)in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated.After 14 days of immersion,no obvious pitting pit was observed on the SS surface ...The corrosion behavior of 304 stainless steel(SS)in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated.After 14 days of immersion,no obvious pitting pit was observed on the SS surface in the sterile medium.By contrast,the SS exhibited serious pitting corrosion with the largest pit depth of 5.0μm in the inoculated medium after 14 days.The results of electrochemical tests showed that the barrier property of the passive film decreased faster in the inoculated medium.The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+and Cr6+increased in the passive film under the influence of archaea N.tibetense,which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion.Combined with the energy starvation tests,the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N.tibetense was discussed finally.展开更多
BACKGROUND Patient-ready duodenoscopes were designed with an assumed contamination rate of less than 0.4%;however,it has been reported that 5.4%of clinically used duodenoscopes remain contaminated with viable high-con...BACKGROUND Patient-ready duodenoscopes were designed with an assumed contamination rate of less than 0.4%;however,it has been reported that 5.4%of clinically used duodenoscopes remain contaminated with viable high-concern organisms despite following the manufacturer’s instructions.Visual inspection of working channels has been proposed as a quality control measure for endoscope reprocessing.There are few studies related to this issue.AIM To investigate the types,severity rate,and locations of abnormal visual inspection findings inside patient-ready duodenoscopes and their microbiological significance.METHODS Visual inspections of channels were performed in 19 patient-ready duodenoscopes using the SpyGlass visualization system in two endoscopy units of tertiary care teaching hospitals(Tri-Service General Hospital and National Taiwan University Hospital)in Taiwan.Inspections were recorded and reviewed to evaluate the presence of channel scratches,buckling,stains,debris,and fluids.These findings were used to analyze the relevance of microbiological surveillance.RESULTS Seventy-two abnormal visual inspection findings in the 19 duodenoscopes were found,including scratches(n=10,52.6%),buckling(n=15,78.9%),stains(n=14,73.7%),debris(n=14,73.7%),and fluids(n=6,31.6%).Duodenoscopes>12 mo old had a significantly higher number of abnormal visual inspection findings than those≤12 mo old(46 findings vs 26 findings,P<0.001).Multivariable regression analyses demonstrated that the bending section had a significantly higher risk of being scratched,buckled,and stained,and accumulating debris than the insertion tube.Debris and fluids showed a significant positive correlation with microbiological contamination(P<0.05).There was no significant positive Spearman’s correlation coefficient between negative bacterial cultures and debris,between that and fluids,and the concomitance of debris and fluids.This result demonstrated that the presence of fluid and debris was associated with positive cultures,but not negative cultures.Further multivariate analysis demonstrated that fluids,but not debris,is an independent factor for bacterial culture positivity.CONCLUSION In patient-ready duodenoscopes,scratches,buckling,stains,debris,and fluids inside the working channel are common,which increase the microbiological contamination susceptibility.The SpyGlass visualization system may be recommended to identify suboptimal reprocessing.展开更多
Algae are reported to be corrosive,while little is known about the role of the algae associated bacteria in the corrosion process.In the present study,Halomonas titanicae was isolated from a culture of an alga strain,...Algae are reported to be corrosive,while little is known about the role of the algae associated bacteria in the corrosion process.In the present study,Halomonas titanicae was isolated from a culture of an alga strain,Spirulina platensis,and identified through 16 S rRNA gene analysis.Corrosion behavior of 304L stainless steel(SS)coupons in the presence and absence of H.titanicae was characterized by using electrochemical measurements and surface analysis.The results showed that H.titanicae significantly accelerated the corrosion rate and decreased the pitting potential of 304L SS in the biotic medium.After removal of the corrosion products and biofilms,severe pitting corrosion caused by H.titanicae was observed.The largest pit depth after 14 d reached 6.6μm,which was 5.5 times higher than that of the sterile control(1.2μm).This is the first report revealing that an alga associated bacterium can induce microbiologically influenced corrosion(MIC),and a further concern is raised that whether algae play a role in the MIC process.展开更多
An antibacterial 2205-Cu duplex stainless steel （DSS） was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu^2＋ ions from the 2205...An antibacterial 2205-Cu duplex stainless steel （DSS） was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu^2＋ ions from the 2205-Cu DSS surface. In this work, the microbiologically influenced corrosion （MIC） resistance of 2205- Cu DS5 in the presence of the corrosive marine bacterium Pseudornonos aeruginosa was investigated. The addition of copper improved the mechanical properties such as the yield strength, the tensile strength and the hardness of 2205 DSS. Electrochemical test results from linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EI5） and critical pitting temperature （CPT） measurements showed that 2205-Cu DSS possessed a larger polarization resistance （Rp）, charge transfer resistance （Rct） and CPT values, indicating the excellent MIC resistance of2205-Cu DSS against the corrosive P. aeruginosa biofilm. The live]dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS. The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14d in the presence ofP. aeruginosa （2.2 μm vs 12.5 μm）. 2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P. aeruginosa.展开更多
The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria （SRB） solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It wa...The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria （SRB） solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It was found that the oxide film was more compact owing to the addition of Sc resulting in the open circuit potential shifting by about 100mV positively. On the other hand, it was seen that the pitting sensitivity of Al-6Mg-Zr-Sc alloy in SRB solution decreased and its microbiologically influenced corrosion resistance was improved. Pitting corrosion occurring on the surface of the two alloys under the comprehensive action of the metabolism of SRB was observed by SEM. It was obtained by EDS that the corrosion degree increased with time and corrosion was furthered by deposition of the product.展开更多
In this article, microbiologically influenced corrosion behavior of Fe3Al intermetallie compound in microorganism culture medium has been investigated by using weight loss methods, electrochemical techniques, and elec...In this article, microbiologically influenced corrosion behavior of Fe3Al intermetallie compound in microorganism culture medium has been investigated by using weight loss methods, electrochemical techniques, and electron microscopy. Polarization curves showed that a sharp electrical current peak caused by surface pitting could be observed after Fe3Al electrodes were immersed in culture medium for 15 days when the polarization potential was about -790 mV vs SCE. Based on the electrochemical impedance spectroscopy （EIS） and the equivalent circuit parameters of the associated system, the corrosion products were found to exhibit a two-layer structured feature and the microorganisms could induce pitting and erosion corrosion of the inner layer. In addition, the passivating film of the inner layer was absolutely destroyed by microbial metabolic products.展开更多
Tetrakis hydroxymethyl phosphonium sulfate(THPS) was enhanced by a 14-mer Peptide A, with its core12-mer sequence mimicking part of Equinatoxin II protein, in the mitigation of sulfate reducing Desulfovibrio ferrophil...Tetrakis hydroxymethyl phosphonium sulfate(THPS) was enhanced by a 14-mer Peptide A, with its core12-mer sequence mimicking part of Equinatoxin II protein, in the mitigation of sulfate reducing Desulfovibrio ferrophilus MIC(microbiologically influenced corrosion) of X80 carbon steel. Results proved that50 ppm(w/w) THPS was sufficient to mitigate the D. ferrophilus biofilm, and its very agressive MIC(19.7mg/cm^(2) in 7 days or 1.31 mm/a), but not 20 ppm THPS. To achieve effective mitigation at a low dosage of THPS, biofilm-dispersing Peptide A was added to 20 ppm THPS in the culture medium. Sessile cell counts were reduced by 2-log and 4-log after enhancement by 10 ppb and 100 ppb Peptide A, respectively. Enhancement efficiency(further reduction in corrosion rate) reached 69% for 10 ppb Peptide A and 83% for100 ppb Peptide A compared with 20 ppm THPS alone treatment, indicating that Peptide A was a good biocide enhancer for THPS.展开更多
In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterizatio...In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterization. The bioelectrochemical, electrochemical, and chemical reactions between X80 steel and microorganisms were investigated comprehensively. The results show that B. licheniformis can accelerate the corrosion of X80 steel substrate in early immersing by two ways: biocatalytic cathodic nitrate reduction and acidification induced by bacterially-secreted acids. However, the corrosion rate of X80 steel decreased after immersing for ca. 1 week in B. licheniformis culture due to iron biomineralization. This work provides direct insights into the mechanism of microbiologically influenced corrosion of carbon steel by the nitrate-reducing bacterium.展开更多
Reports on corrosion failure of cable bolts,used in mining and civil industries,have been increasing in the past two decades.The previous studies found that pitting corrosion on the surface of a cable bolt can initiat...Reports on corrosion failure of cable bolts,used in mining and civil industries,have been increasing in the past two decades.The previous studies found that pitting corrosion on the surface of a cable bolt can initiate premature failure of the bolt.In this study,the role of Acidithiobacillus ferrooxidans(A.ferrooxidans)bacterium in the occurrence of pitting corrosion in cable bolts was studied.Stressed coupons,made from the wires of cable bolts,were immersed in testing bottles containing groundwater collected from an underground coal mine and a mixture of A.ferrooxidans and geomaterials.It was observed that A.ferrooxidans caused pitting corrosion on the surface of cable bolts in the near-neutral environment.The presence of geomaterials slightly affected the p H of the environment;however,it did not have any significant influence on the corrosion activity of A.ferrooxidans.This study suggests that the common bacterium A.ferrooxidans found in many underground environments can be a threat to cable bolts'integrity by creating initiation points for other catastrophic failures such as stress corrosion cracking.展开更多
基金supported by the Hubei Provincial Natural Science Foundation of China(No.2023AFB646)Knowledge Innovation Program of Wuhan(No.2023020201010155)Educational Research Program of Huazhong University of Science and Technology(No.2022135).
文摘Objective and Background Early and accurate diagnosis of spinal infections,including spinal tuberculosis,is pivotal for effective treatment but remains challenging.This study aims to assess the diagnostic yield of metagenomic next-generation sequencing(mNGS)compared with that of conventional microbiological tests(CMTs)in identifying pathogens associated with spinal pathologies,with a special focus on infections leading to surgical interventions.Methods We enrolled 85 patients who underwent spinal surgery,comprising 63 patients with clinically diagnosed spinal infections,including patients with spinal tuberculosis,and 22 patients with noninfectious spinal conditions.The procedures involved irrigation and debridement for persistent wound drainage,with subsequent DNA extraction from plasma and joint fluid for mNGS and CMT analysis.Results Significantly increased C-reactive protein(CRP)levels were observed in patients with infections.The mNGS approach showed greater diagnostic sensitivity(92.06%)for detecting pathogens,including Mycobacterium tuberculosis,than did CMTs(36.51%).Despite its low specificity,mNGS had considerable negative predictive value(70.59%),underscoring its utility in ruling out infections.Conclusions The mNGS offers superior sensitivity over CMTs in the diagnosis of a variety of spinal infections,notably spinal tuberculosis.This study highlights the potential of mNGS in enhancing the diagnosis of complex spinal infections,thereby informing targeted treatment strategies.
文摘A total of fifty (50) samples of water from Lake Fitri (Chad), with 25 samples per island (Domoro and Maguite). The aim of this study was to analyze the bacteriological, biochemical and physico-chemical quality of the water in Lake Fitri in Chad. Standard microbiology methods were used. Isolated strains of enterobacteria were characterized by API 20E and API Staph galleries and confirmed by API Web. Antibiotic resistance was performed according to the recommendations of the antibiogram committee (CA-SFM, 2019). Physico-chemical analysis of the water was carried out by (Rodier, 2009). The microbiological results revealed an abundance on the Domoro islands (5.37.106 ± 1.5.105 and 1.97.105 ± 4.94.104), successively for total aerobic mesophilic flora (FMAT), and thermotolerant coliform (E. coli) and on the Maguite Islands (4.71.106 ± 7.14.105 and 2.32.105 ± 2.86.104), alternately for total aerobic mesophilic flora (FMAT), and thermotolerant coliform (E. coli). The results obtained after incubation of the biochemical tests using the API 20E and API Staph galleries and their proposed numerical profile analyzed using Api software and confirmed by Api Web confirmed the contamination of the waters of Lake Fitri by pathogenic strains of E. coli, Staphylococcus and Salmonella spp. The results of the antibiogram carried out show the emergence of certain resistances to Tobramycin, Flucytosine and Teicoplanin. The average levels of BOD5, COD, SS, Nitrate (NO3) and Nitrite (NO2) for Domoro Island were 32.14 ± 2.37 mg/L, 423.86 ± 4.78 mg/L, 65.42 ± 2.27 mg/L, 0.04 ± 0.01 mg/L and 3.32 ± 1.48 mg/L respectively. The water from the islands of Lake Fitri must therefore be rigorously treated before consumption.
文摘AIM:To determine the microbiological agents and antibiotic susceptibility of chronic dacryocystitis in recent years to guide effective treatment strategies.METHODS:A total of 308 adult patients with chronic dacryocystitis were enrolled from January 2020 to September 2022 in Beijing Tongren Hospital.The 229 pus specimens were taken from the conjunctival sac,while 79 specimens were taken from the opened lacrimal sac during transnasal dacryocystorhinostomy(DCR)surgery.All the samples were sent for microbiological smear and culture and drug susceptibility tests.RESULTS:The 202 specimens showed microbial growth,with a positive rate of 65.6%.The 313 strains of bacteria were isolated,including 272 aerobic or facultative anaerobes,accounting for 86.9%,and 41 anaerobic bacteria,accounting for 13.1%.The most common strains were Staphylococcus epidermidis,Corynebacterium macginleyi,and Staphylococcus aureus.Six strains of fungi were isolated.The 14 strains(18.9%)of Staphylococcus were found to be multidrug resistant.It showed a wide variety of gram-negative bacteria,up to 23 species.Specimens obtained during DCR surgery had a positive rate of 70.9%,which was higher than those obtained from the conjunctival sac(63.8%),with a statistically significant difference.More microbiological species were found in intraoperative specimens,and consisted largely of pathogenic bacteria or conditional pathogens.All the 6 strains of fungi were obtained from intraoperative specimens.All bacteria were sensitive to vancomycin,while a large number of bacteria were resistant to erythromycin.The commonly used ocular antibiotics levofloxacin,moxifloxacin and tobramycin were generally sensitive to most of the bacteria.CONCLUSION:Gram-positive cocci,gram-positive bacilli,and gram-negative bacilli are the predominant pathogens for chronic dacryocystitis.Specimens taken during DCR surgery can obtain more accurate microbiological results.
文摘In aquaculture, feed represents the main component of production costs, and the development of this sector depends on the development of an economical feed formulation that meets the qualitative and quantitative requirements of fish. The aim of this study was to determine the nutritive and microbiological quality of fish feed formulated from local flours enriched with Hermetia illucens larvae. The raw materials used for formulation were fishmeal, corn meal, low-grade rice, soybean meal and Hermetia illucens larvae meal. Different iso-protein feed compositions were prepared with 0%, 10%, 25%, 35%, 50%, 65%, 75% and 100% incorporation of Hermetia illucens larvae meal as a substitute for fish meal. Biochemical and microbiological analyses of these flours were determined using standard methods. The results showed that incorporation of larvae meal had an influence on the biochemical characteristics ash (8.15 to 20.27%), lipid (11.55 to 24.94%), fiber (13.93 to 20.41%) and dry matter (89.65 to 91.19%) of various formulated feed. Loads of fecal Streptococci, Staphylococci, Aeromonas, yeasts and molds ranged from 2.4 to 4.9 log 10 CFU/g;3.6 to 3.9 log 10 CFU/g;2.2 to 2.7 log 10 CFU/g;2.1 to 2.3 log 10 CFU/g, respectively. The level of contamination of these flours was below the microbiological criteria applicable to animal feed. Feed formulated with 0% and 10% Hermetia illucens larvae showed the best nutritive and microbiological characteristics. These results suggest that flours enriched with Hermetia illucens larvae could be used in fish feed.
文摘Forty-nine microbial strains were used to screen their ability for the microbiological transforma-tion of ginsenoside Rg1. Aspergillus niger (3.1858) and Absidia coerulea (3.3538) were found to convert ginsenoside Rg1 efficiently to less polar metabolites. Preparative scale transformation with both fungi Absidia coerulea (3.3538) and Aspergillus niger (3.1858) have resulted in the production of one same metabolite (MT1). Its structure was char-acterized as 6-O-b-D-glucopyranosyl-20(S)-protopanaxatriol (Ginsenoside Rh1) on the basis of its TOF-MS and 1H, 13C NMR spectral data. The biotransformation kinetic curves for Ginsenoside Rg1 and MT1 were reported for the first time, and the biotransformation pathway was proposed.
文摘Salicylate is a type of pollutant widely and persistently existed in environ- ment. Microbiological degradation of salicylate as one kind of biological remediation methods has the advantages of low cost, good effect and no secondary pollution, and also attracts wide attention both at home and abroad. Currently, many salicy- late-degrading bacteria are isolated and screened, while the molecular mechanism of salicylate metabolism is also worth deep research. The research about molecular mechanism of microorganism degradation was overviewed, various degrading path- ways including catechol meta-cleavage pathway and gentisate pathway were intro- duced, and the latest progress in regulating genes of salicylate degradation was summarized.
基金funding by the National Natural Science Foundation of China (Nos.51501203 and U1660118)the National Basic Research Program of China (973 Program Project,No.2014CB643300)+1 种基金the National Environmental Corrosion Platform (NECP)T.U.is sponsored by a postdoctoral fellowship from The Scientific and Technological Research Council of Turkey (TUBITAK-2219)
文摘Sulfate reducing bacteria(SRB) are often the culprits of microbiologically influenced corrosion(MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H_2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H_2S gets its H^+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H_2S is responsible for SRB MIC of carbon steel. However, in recent years,well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer(EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.
基金supported by Science Foundation of China University of Petroleum,Beijing(Nos.2462017YJRC038 and 2462018BJC005)supported by the National Natural Science Foundation of China(Grant U1660118)+1 种基金the National Basic Research Program of China(973 Program,No.2014CB643300)the National Environmental Corrosion Platform(NECP)
文摘Microbiologically influenced corrosion （MIC） is a major cause of corrosion damages, facility failures, and financial losses, making MIC an important research topic. Due to complex microbiological activities and a lack of deep understanding of the interactions between biofilms and metal surfaces, MIC occurrences and mechanisms are difficult to predict and interpret. Many theories and mechanisms have been pro- posed to explain MIC. In this review, the mechanisms of MIC are discussed using hioenergetics, microbial respiration types, and biofilm extracellular electron transfer （EET）. Two main MIC types, namely EET-MIC and metabolite MIC （M-ME）, are discussed. This brief review provides a state of the art insight into MIC mechanisms and it helps the diagnosis and prediction of occurrences of MIC under anaerobic conditions in the oil and gas industry.
基金supportedfinancially by the National Natural Science Foundation of China(No.U1660118)the National Basic Research Program of China(No.2014CB643300)the National Environmental Corrosion Platform(NECP)
文摘Microbiologically influenced corrosion(MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorganisms cause severe deterioration on the metals. In this study, MIC of pure titanium(Ti) was studied in the presence of a highly corrosive aerobic marine bacterium Pseudomonas aeruginosa. The results obtained from electrochemical test showed that Ti was corrosion resistant in the abiotic culture medium after 14 d, while the increased corrosion current density(i_(corr)) obtained from polarization curves and the decreased charge transfer resistance(R_(ct)) from electrochemical impedance spectroscopy(EIS)indicated the accelerated corrosion of Ti caused by P. aeruginosa biofilm. For further confirmation of the above results, the surface of Ti was investigated using scanning electron microscopy(SEM), confocal laser scanning microscopy(CLSM) and X-ray photoelectron spectroscopy(XPS). According to the XPS results, TiO_2 was formed in both abiotic and biotic conditions, while unstable oxide Ti_2O_3 was detected in the presence of P. aeruginosa, leading to the defects in the passive film and localized corrosion. Pitting corrosion was investigated with the help of CLSM, and the largest pit depth found on Ti surface immersed in P. aeruginosa was 1.2 μm. Ti was not immune to MIC caused by P. aeruginosa.
基金supported financially by the National Key R&D Program of China (No. 2016YFB0300604)the National Natural Science Foundation of China (Nos. 51575510 and 51771221)
文摘The TiSiN-Cu nanocomposite coating was deposited on F690 steel substrate by arc ion plating. The structure and composition, tribocorrosion behavior and anti-microbiologically influenced corrosion(MIC)properties of TiSiN-Cu coating were investigated. The results show that the TiSiN-Cu coating has unique nanocomposite structures. The results of tribocorrosion show that the potential and current change of F690 steel and TiSiN-Cu coatings tend to be opposite. The reason is that the F690 steel is non-passivated metal and the TiSiN-Cu coating has passivation phenomenon. The TiSiN-Cu coating possesses excellent tribocorrosion resistance. Cu ion released from TiSiN-Cu coating can effectively inhibit the corrosion caused by SRB.
文摘Objective:To investigate the quality of indoor air of different wards and units of Olabisi Onabanjo University Teaching Hospital, Sagamu, to ascertain their contribution to infection rate in the hospital.Methods:The microbial quality of indoor air of nine wards/units of Olabisi Onabanjo University Teaching Hospital, Sagamu, Nigeria was conducted. Sedimentation technique using open Petri-dishes containing different culture media was employed and samplings were done twice daily, one in the morning shortly after cleaning and before influx of people/patients into the wards/units and the other in the evening when a lot of activities would have taken place in these wards. Isolates were identified according to standard methods.Results:Results showed that there was a statistically significant difference(氈2= 6.0167) in the bacteria population of the different sampling time whereas it was not so for fungi population(氈2= 0.2857). Male medical ward(MMW) and male surgical general(MSG) recorded the highest bacterial and fungal growth while the operating theatre(OT) was almost free of microbial burden. The bacteria isolates were Staphylococcus aureus, Klebsiellasp., Bacillus cereus, Bacillus subtilis, Streptococcus pyogenes andSerratia marscenceswhile the fungi isolates includedAspergillus flavus, Penicilliumsp.,Fusariumsp.,Candida albicansandAlternariasp.Staphylococcus aureuswas the predominantly isolated bacterium whilePenicilliumsp. was the most isolated fungus.Conclusions:Though most of the microbial isolates were potential and or opportunistic pathogens, there was no correlation between the isolates in this study and the surveillance report of nosocomial infection during the period of study, hence the contribution of the indoor air cannot be established. From the reduction noticed in the morning samples, stringent measures such as proper disinfection and regular cleaning, restriction of patient relatives' movement in and out of the wards/units need to be enforced so as to improve the quality of indoor air of our hospital wards/units.
基金the Beijing Nova Program(No.Z171100001117076)the National Natural Science Foundation of China(Nos.51871026,51771029)the National Environmental Corrosion Platform。
文摘The corrosion behavior of 304 stainless steel(SS)in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated.After 14 days of immersion,no obvious pitting pit was observed on the SS surface in the sterile medium.By contrast,the SS exhibited serious pitting corrosion with the largest pit depth of 5.0μm in the inoculated medium after 14 days.The results of electrochemical tests showed that the barrier property of the passive film decreased faster in the inoculated medium.The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+and Cr6+increased in the passive film under the influence of archaea N.tibetense,which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion.Combined with the energy starvation tests,the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N.tibetense was discussed finally.
基金Ministry of Defense-Medical Affairs Bureau,Tri-Service General Hospital,No.TSGH-D-109182.
文摘BACKGROUND Patient-ready duodenoscopes were designed with an assumed contamination rate of less than 0.4%;however,it has been reported that 5.4%of clinically used duodenoscopes remain contaminated with viable high-concern organisms despite following the manufacturer’s instructions.Visual inspection of working channels has been proposed as a quality control measure for endoscope reprocessing.There are few studies related to this issue.AIM To investigate the types,severity rate,and locations of abnormal visual inspection findings inside patient-ready duodenoscopes and their microbiological significance.METHODS Visual inspections of channels were performed in 19 patient-ready duodenoscopes using the SpyGlass visualization system in two endoscopy units of tertiary care teaching hospitals(Tri-Service General Hospital and National Taiwan University Hospital)in Taiwan.Inspections were recorded and reviewed to evaluate the presence of channel scratches,buckling,stains,debris,and fluids.These findings were used to analyze the relevance of microbiological surveillance.RESULTS Seventy-two abnormal visual inspection findings in the 19 duodenoscopes were found,including scratches(n=10,52.6%),buckling(n=15,78.9%),stains(n=14,73.7%),debris(n=14,73.7%),and fluids(n=6,31.6%).Duodenoscopes>12 mo old had a significantly higher number of abnormal visual inspection findings than those≤12 mo old(46 findings vs 26 findings,P<0.001).Multivariable regression analyses demonstrated that the bending section had a significantly higher risk of being scratched,buckled,and stained,and accumulating debris than the insertion tube.Debris and fluids showed a significant positive correlation with microbiological contamination(P<0.05).There was no significant positive Spearman’s correlation coefficient between negative bacterial cultures and debris,between that and fluids,and the concomitance of debris and fluids.This result demonstrated that the presence of fluid and debris was associated with positive cultures,but not negative cultures.Further multivariate analysis demonstrated that fluids,but not debris,is an independent factor for bacterial culture positivity.CONCLUSION In patient-ready duodenoscopes,scratches,buckling,stains,debris,and fluids inside the working channel are common,which increase the microbiological contamination susceptibility.The SpyGlass visualization system may be recommended to identify suboptimal reprocessing.
基金supported financially by the National Natural Science Foundation of China(Nos.U1660118 and 51871050)the National Environmental Corrosion Platform(NECP)of Chinathe Fundamental Research Funds for the Central Universities of Ministry of Education of China(No.N180205021).
文摘Algae are reported to be corrosive,while little is known about the role of the algae associated bacteria in the corrosion process.In the present study,Halomonas titanicae was isolated from a culture of an alga strain,Spirulina platensis,and identified through 16 S rRNA gene analysis.Corrosion behavior of 304L stainless steel(SS)coupons in the presence and absence of H.titanicae was characterized by using electrochemical measurements and surface analysis.The results showed that H.titanicae significantly accelerated the corrosion rate and decreased the pitting potential of 304L SS in the biotic medium.After removal of the corrosion products and biofilms,severe pitting corrosion caused by H.titanicae was observed.The largest pit depth after 14 d reached 6.6μm,which was 5.5 times higher than that of the sterile control(1.2μm).This is the first report revealing that an alga associated bacterium can induce microbiologically influenced corrosion(MIC),and a further concern is raised that whether algae play a role in the MIC process.
基金financially supported by the National Natural Science Foundation of China(Nos.51501203 and U1660118)Shenzhen Science and Technology Research Funding(No.JCYJ20160608153641020)+1 种基金the National Basic Research Program of China(No.2014CB643300)the National Environmental Corrosion Platform(NECP)
文摘An antibacterial 2205-Cu duplex stainless steel （DSS） was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu^2＋ ions from the 2205-Cu DSS surface. In this work, the microbiologically influenced corrosion （MIC） resistance of 2205- Cu DS5 in the presence of the corrosive marine bacterium Pseudornonos aeruginosa was investigated. The addition of copper improved the mechanical properties such as the yield strength, the tensile strength and the hardness of 2205 DSS. Electrochemical test results from linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EI5） and critical pitting temperature （CPT） measurements showed that 2205-Cu DSS possessed a larger polarization resistance （Rp）, charge transfer resistance （Rct） and CPT values, indicating the excellent MIC resistance of2205-Cu DSS against the corrosive P. aeruginosa biofilm. The live]dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS. The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14d in the presence ofP. aeruginosa （2.2 μm vs 12.5 μm）. 2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P. aeruginosa.
基金Project supported by the National Natural Science Foundation of China (50571003)
文摘The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria （SRB） solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It was found that the oxide film was more compact owing to the addition of Sc resulting in the open circuit potential shifting by about 100mV positively. On the other hand, it was seen that the pitting sensitivity of Al-6Mg-Zr-Sc alloy in SRB solution decreased and its microbiologically influenced corrosion resistance was improved. Pitting corrosion occurring on the surface of the two alloys under the comprehensive action of the metabolism of SRB was observed by SEM. It was obtained by EDS that the corrosion degree increased with time and corrosion was furthered by deposition of the product.
基金sponsored by the National Natural Science Foundation of China(Nos.50692090 and 50842061)the School Funds of Ocean University of China(2009126)
文摘In this article, microbiologically influenced corrosion behavior of Fe3Al intermetallie compound in microorganism culture medium has been investigated by using weight loss methods, electrochemical techniques, and electron microscopy. Polarization curves showed that a sharp electrical current peak caused by surface pitting could be observed after Fe3Al electrodes were immersed in culture medium for 15 days when the polarization potential was about -790 mV vs SCE. Based on the electrochemical impedance spectroscopy （EIS） and the equivalent circuit parameters of the associated system, the corrosion products were found to exhibit a two-layer structured feature and the microorganisms could induce pitting and erosion corrosion of the inner layer. In addition, the passivating film of the inner layer was absolutely destroyed by microbial metabolic products.
基金financial support from Saudi Aramcothe China Scholarship Council for studying in the USA+2 种基金supports by the National Key Research and Development Program of China (No. 2018YFF0215002)Key Laboratory of Materials Chemistry for Energy Conversion and Storage Ministry of Education (2018)The Foundation of Hubei Key Laboratory of Materials Chemistry and Service Failure (2017)。
文摘Tetrakis hydroxymethyl phosphonium sulfate(THPS) was enhanced by a 14-mer Peptide A, with its core12-mer sequence mimicking part of Equinatoxin II protein, in the mitigation of sulfate reducing Desulfovibrio ferrophilus MIC(microbiologically influenced corrosion) of X80 carbon steel. Results proved that50 ppm(w/w) THPS was sufficient to mitigate the D. ferrophilus biofilm, and its very agressive MIC(19.7mg/cm^(2) in 7 days or 1.31 mm/a), but not 20 ppm THPS. To achieve effective mitigation at a low dosage of THPS, biofilm-dispersing Peptide A was added to 20 ppm THPS in the culture medium. Sessile cell counts were reduced by 2-log and 4-log after enhancement by 10 ppb and 100 ppb Peptide A, respectively. Enhancement efficiency(further reduction in corrosion rate) reached 69% for 10 ppb Peptide A and 83% for100 ppb Peptide A compared with 20 ppm THPS alone treatment, indicating that Peptide A was a good biocide enhancer for THPS.
基金financially supported by the National Natural Science Foundation of China (No. 51871026)the National Key R&D Program of China (No. 2017YFF0210404)。
文摘In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterization. The bioelectrochemical, electrochemical, and chemical reactions between X80 steel and microorganisms were investigated comprehensively. The results show that B. licheniformis can accelerate the corrosion of X80 steel substrate in early immersing by two ways: biocatalytic cathodic nitrate reduction and acidification induced by bacterially-secreted acids. However, the corrosion rate of X80 steel decreased after immersing for ca. 1 week in B. licheniformis culture due to iron biomineralization. This work provides direct insights into the mechanism of microbiologically influenced corrosion of carbon steel by the nitrate-reducing bacterium.
基金funding provided by the Australian Research Council(ARC)Linkage Projects(Nos.100200238 and 140100153)supported by Jennmar Australia Pty Ltd+5 种基金Glencore Australia Holdings Pty LtdIllawarra Coal Holdings Pty LtdSpringvale Coal Pty LtdAnglo Operations Pty LtdAnglo Coal AustraliaNarrabri Coal Operations Pty Ltd。
文摘Reports on corrosion failure of cable bolts,used in mining and civil industries,have been increasing in the past two decades.The previous studies found that pitting corrosion on the surface of a cable bolt can initiate premature failure of the bolt.In this study,the role of Acidithiobacillus ferrooxidans(A.ferrooxidans)bacterium in the occurrence of pitting corrosion in cable bolts was studied.Stressed coupons,made from the wires of cable bolts,were immersed in testing bottles containing groundwater collected from an underground coal mine and a mixture of A.ferrooxidans and geomaterials.It was observed that A.ferrooxidans caused pitting corrosion on the surface of cable bolts in the near-neutral environment.The presence of geomaterials slightly affected the p H of the environment;however,it did not have any significant influence on the corrosion activity of A.ferrooxidans.This study suggests that the common bacterium A.ferrooxidans found in many underground environments can be a threat to cable bolts'integrity by creating initiation points for other catastrophic failures such as stress corrosion cracking.
