Objective:Burkholderiagladioli(B.gladioli)pathovar cocovenenans(BG),a foodborne pathogen,can cause lethal poisoning.Most cases have been reported_in China,primarily originating from fermented cereal products.In this s...Objective:Burkholderiagladioli(B.gladioli)pathovar cocovenenans(BG),a foodborne pathogen,can cause lethal poisoning.Most cases have been reported_in China,primarily originating from fermented cereal products.In this study,we investigated the prevalence of BGC contamination in commercially available fungi and analyzed the environmental conditions for bongkrekic acid(BA)production in Shanghai.BA testing and animal experiments were conducted to confirm the relationship between bon genes and BA biosynthesis,and to clarify the causes of poisoning.Methods:The association between the bon gene cluster and BA synthesis was analyzed through whole-genome sequencing and animal testing to identify the gene cluster responsible for BA synthesis.Results:The overall detection rate of B.gladioli in the 85 samples was 44.7%(38/85).The highest detection rate was in dried black fungus(94.4%;34/36),followed by fresh Tremella fuciformnis(T.fuciformis)(16.6%;2/12),fresh black fungus(9.1%;1/11),and dried T.fuciformis(3.8%;1/26).BGC was detected only in dried black fungus,with a detection rate of 39%(14/36).In the crude extract solutions obtained from the 14 BGC cultures,BA concentrations ranged from 0.33 μg/mL to 714.83 μg/mL.Both the crude extract solution and the ten.-fold concentrated solution caused death in mice.Conclusion:The results of this study demonstrate that all BGC strains carry the bon gene cluster encoding BA,indicating that bonABCDFGHIJKLM plays an essential role in the biosynthesis of BA.展开更多
Three hrfA (hypersensitive response-functioning faction A) homologues (hrf1, hrf2 and hrf3) are cloned from 12 strains of Xanthomonas oryzae using PCR based techniques. Hrf1, hrf2 and hrf3 are derived from strains bel...Three hrfA (hypersensitive response-functioning faction A) homologues (hrf1, hrf2 and hrf3) are cloned from 12 strains of Xanthomonas oryzae using PCR based techniques. Hrf1, hrf2 and hrf3 are derived from strains belonging to X. o. pv. oryzae, X. o. pv. oryzicola and X. o. pv. oryzae respectively. Sequence analysis shows that all three genes encode glycine-rich pro-teins with various numbers of GGG-GG motifs. They all share a conserved cysteine residue at position 45 or 47. Hrf1 and hrf3 encode HarpinXoo while hrf2 encodes Harpinxooc. Hrf1 and hrf3 encodes two different types of HarpinXoo proteins. Hrf1 from X. o. pv. oryzae strains ( JxoIII, JxoIV, Jxov, Pxo61, Pxo76, Pxo79, Pxo99, Pxo99 and Pxo124) encodes a 15.6 kD HarpinXoo with 3 GGG-GG motifs while Hrf3 from strain Pxo86 and Pxo112 encodes a 15.9 kD Harpinxoo with 4 GGG-GG motifs. Harpinxooc encoded by hrf2 from X. o. pv. oryzicola (strain RS105) has the mo-lecular weight of 15.3 kD and contains 2 GGG-GG motifs. Cluster analysis is performed using deduced sequences of hrf1, hrf2 and hrf3 as well as previously reported Hpa1 and XopI protein sequence. The results indicated that Harpinxoo and Harpinxooc belong to two closely related sub-groups. Hrf, hrf2 and hrf3 are expressed in E. coli strain BL21 successfully. Under the same condition, hrf1, hrf2 and hrf3 are expressed at the level of 0.389, 0.530 and 0.083 mg/mL re-spectively. All expressed hrf1, hrf2 and hrf3 proteins (Harpins) are shown to be able to induce hypersensitive reaction and TMV resistance on tobacco. Among the three proteins, Hrf2 has the highest activity while Hrf3 has the lowest activity.展开更多
Pseudomonas syringae is the most frequently emerging group of plant pathogenic bacteria.Because this bacterium is ubiquitous as an epiphyte and on various substrates in non-agricultural settings,there are many questio...Pseudomonas syringae is the most frequently emerging group of plant pathogenic bacteria.Because this bacterium is ubiquitous as an epiphyte and on various substrates in non-agricultural settings,there are many questions about how to assess the risk for plant disease posed by strains in the environment.Although P.syringae is considered to have discrete host ranges in defined pathovars,there have been few reports of comprehensive comparisons of host range potential.Here we present results of host range tests for 134 strains,representing eight phylogroups,from epidemics and environmental reservoirs on 15 to 22 plant species per test conducted in four separate tests to determine the patterns and extent of host range.We sought to identify trends that are indicative of distinct pathotypes and to assess if strains in the P.syringae complex are indeed restricted in their host range.We show that for each test,strains display a diversity of host ranges from very restricted to very broad regardless of the gamut of phylogroups used in the test.Overall,strains form an overlapping continuum of host range potential with equal representation of narrow,moderate and broad host ranges.Groups of distinct pathotypes,including strains with currently the same pathovar name,could not be identified.The absence of groupings was validated with statistical tests for pattern recognition.The extent of host range was positively correlated with the capacity of strains to swarm on semi-solid agar medium and with the abundance of genes in biosynthetic clusters and was inversely correlated with the abundance of genes for proteins with transmembrane domains in their genomes.Our results are consistent with the current paradigm that disease symptoms are the result of multiple molecular interactions between P.syringae and its plant host that are modulated by abiotic and biotic conditions.This leads us to propose that pathovar denominations do not correspond to the underlying biology of P.syringae.A new concept of pathogenicity that accounts for the continuum of pathogenic potential in P.syringae would open new perspectives to understand the evolution of pathogenicity in this bacterium and new insights to anticipate disease and to manage plant health.展开更多
基金Supported by the Three-Year Initiative Plan for Strengthening Public Health System Construction in Shanghai(GW Ⅵ-3).
文摘Objective:Burkholderiagladioli(B.gladioli)pathovar cocovenenans(BG),a foodborne pathogen,can cause lethal poisoning.Most cases have been reported_in China,primarily originating from fermented cereal products.In this study,we investigated the prevalence of BGC contamination in commercially available fungi and analyzed the environmental conditions for bongkrekic acid(BA)production in Shanghai.BA testing and animal experiments were conducted to confirm the relationship between bon genes and BA biosynthesis,and to clarify the causes of poisoning.Methods:The association between the bon gene cluster and BA synthesis was analyzed through whole-genome sequencing and animal testing to identify the gene cluster responsible for BA synthesis.Results:The overall detection rate of B.gladioli in the 85 samples was 44.7%(38/85).The highest detection rate was in dried black fungus(94.4%;34/36),followed by fresh Tremella fuciformnis(T.fuciformis)(16.6%;2/12),fresh black fungus(9.1%;1/11),and dried T.fuciformis(3.8%;1/26).BGC was detected only in dried black fungus,with a detection rate of 39%(14/36).In the crude extract solutions obtained from the 14 BGC cultures,BA concentrations ranged from 0.33 μg/mL to 714.83 μg/mL.Both the crude extract solution and the ten.-fold concentrated solution caused death in mice.Conclusion:The results of this study demonstrate that all BGC strains carry the bon gene cluster encoding BA,indicating that bonABCDFGHIJKLM plays an essential role in the biosynthesis of BA.
基金This work was supported the National Key Basic Research Plan of China(973-G20000016201,2003CB 114204)National Natural Science Foundation of China(Grant No.30230240)Science and Technology Plan of Nanjing(2002ZB0114).
文摘Three hrfA (hypersensitive response-functioning faction A) homologues (hrf1, hrf2 and hrf3) are cloned from 12 strains of Xanthomonas oryzae using PCR based techniques. Hrf1, hrf2 and hrf3 are derived from strains belonging to X. o. pv. oryzae, X. o. pv. oryzicola and X. o. pv. oryzae respectively. Sequence analysis shows that all three genes encode glycine-rich pro-teins with various numbers of GGG-GG motifs. They all share a conserved cysteine residue at position 45 or 47. Hrf1 and hrf3 encode HarpinXoo while hrf2 encodes Harpinxooc. Hrf1 and hrf3 encodes two different types of HarpinXoo proteins. Hrf1 from X. o. pv. oryzae strains ( JxoIII, JxoIV, Jxov, Pxo61, Pxo76, Pxo79, Pxo99, Pxo99 and Pxo124) encodes a 15.6 kD HarpinXoo with 3 GGG-GG motifs while Hrf3 from strain Pxo86 and Pxo112 encodes a 15.9 kD Harpinxoo with 4 GGG-GG motifs. Harpinxooc encoded by hrf2 from X. o. pv. oryzicola (strain RS105) has the mo-lecular weight of 15.3 kD and contains 2 GGG-GG motifs. Cluster analysis is performed using deduced sequences of hrf1, hrf2 and hrf3 as well as previously reported Hpa1 and XopI protein sequence. The results indicated that Harpinxoo and Harpinxooc belong to two closely related sub-groups. Hrf, hrf2 and hrf3 are expressed in E. coli strain BL21 successfully. Under the same condition, hrf1, hrf2 and hrf3 are expressed at the level of 0.389, 0.530 and 0.083 mg/mL re-spectively. All expressed hrf1, hrf2 and hrf3 proteins (Harpins) are shown to be able to induce hypersensitive reaction and TMV resistance on tobacco. Among the three proteins, Hrf2 has the highest activity while Hrf3 has the lowest activity.
基金supported by in-house funding from INRA and from the Ministry of Education,Science and Technological Development of Serbia,grant No.173026.The salary of JRL was supported by DAFNE,University of TusciaThe sojourn of IN to conduct pathogenicity tests in Avignon was supported by a Research Grant from the Federation of European Microbiology Societies.
文摘Pseudomonas syringae is the most frequently emerging group of plant pathogenic bacteria.Because this bacterium is ubiquitous as an epiphyte and on various substrates in non-agricultural settings,there are many questions about how to assess the risk for plant disease posed by strains in the environment.Although P.syringae is considered to have discrete host ranges in defined pathovars,there have been few reports of comprehensive comparisons of host range potential.Here we present results of host range tests for 134 strains,representing eight phylogroups,from epidemics and environmental reservoirs on 15 to 22 plant species per test conducted in four separate tests to determine the patterns and extent of host range.We sought to identify trends that are indicative of distinct pathotypes and to assess if strains in the P.syringae complex are indeed restricted in their host range.We show that for each test,strains display a diversity of host ranges from very restricted to very broad regardless of the gamut of phylogroups used in the test.Overall,strains form an overlapping continuum of host range potential with equal representation of narrow,moderate and broad host ranges.Groups of distinct pathotypes,including strains with currently the same pathovar name,could not be identified.The absence of groupings was validated with statistical tests for pattern recognition.The extent of host range was positively correlated with the capacity of strains to swarm on semi-solid agar medium and with the abundance of genes in biosynthetic clusters and was inversely correlated with the abundance of genes for proteins with transmembrane domains in their genomes.Our results are consistent with the current paradigm that disease symptoms are the result of multiple molecular interactions between P.syringae and its plant host that are modulated by abiotic and biotic conditions.This leads us to propose that pathovar denominations do not correspond to the underlying biology of P.syringae.A new concept of pathogenicity that accounts for the continuum of pathogenic potential in P.syringae would open new perspectives to understand the evolution of pathogenicity in this bacterium and new insights to anticipate disease and to manage plant health.
