Climate change may threaten the survival of corals due to ocean warming and increased occurrence of extreme weather events.Yet,marginal coral communities demonstrate remarkable adaptability,largely due to stress-toler...Climate change may threaten the survival of corals due to ocean warming and increased occurrence of extreme weather events.Yet,marginal coral communities demonstrate remarkable adaptability,largely due to stress-tolerant species.The mechanisms underlying their resilience to environmental fluctuations remains largely unexplored.Here,we investigated 3 coral species(Cyphastrea serailia,Dipsastraea speciosa,and Duncanopsammia peltata)living at the northern edge of their distribution along the South China coast(Dongshan).Combining physiological and stable isotope analysis,we assessed their traits(symbiont characteristics,C:N ratio,and biomass)and trophic flexibility(i.e.,shifts in isotopic niche or nutritional mode)in response to environmental fluctuations across seasons(autumn,winter,and late spring).Our results revealed distinct physiological traits among these corals,but consistently showed lower symbiont density,higher biomass,and increased chlorophyll content in winter.All corals highly relied on heterotrophy as a crucial adaptive response(consistently no overlap between host and symbiont isotopic niches),but they differed in the degree of trophic plasticity,with D.speciosa showing the highest variability in heterotrophic contribution(36.3%across seasons),followed by C.serailia(21.8%)and D.peltata(8.6%).Notably,the species-specific differences in trophic plasticity well corresponded to the variation in overall isotopic niche and coral distribution.As such,trophic plasticity may play a role in shaping spatial distribution of corals in the marginal community.Overall,this study enhances our understanding of coral resilience in marginal communities and offer new insights into possible mechanisms driving the distribution of reef-building corals in the changing ocean.展开更多
The effects of several nutritional factors on the growth and eicosapentaenoic acid （EPA） production of diatom Nitzschia laevis were studied. 4LDM （quadrupled concentration of the nutrient salt） was the optimal con...The effects of several nutritional factors on the growth and eicosapentaenoic acid （EPA） production of diatom Nitzschia laevis were studied. 4LDM （quadrupled concentration of the nutrient salt） was the optimal concentration of nutrient salt for the growth and EPA production ofN. laevis. The growth ofN. laevis was inhibited when the glucose concentration was either lower than 10gL^-1 or higher than 15 gL^-1. Both sodium nitrate and urea were good nitrogen sources for the growth and EPA production, while ammonium chloride seriously decreased the dry cell weight （DW） and the EPA content. Silicate seriously influenced the growth of N. laevis. The maximum DW of 2.34 gL^-1 was obtained in the presence of 150 mgL^-1 Na2SiO3· 9H2O. The EPA content remained almost the same when the silicate concentration was lower than 150mgL^-1; however, higher silicate concentrations resulted in a steady decrease of EPA content. Low medium salinity （≤29） did not seem to influence the DW of N. laevis, and high salinity resulted in a decrease of DW. The highest EPA content （4.08%） and yield （110mgL^-1） were observed at the salinity of 36 and 29, respectively. Key words polyunsaturated fatty acid; eicosapentaenoic acid; microalga; Nitzschia laevis; heterotrophy展开更多
One isolate of Brachiomonas submarina was tested for its ability to grow heterotrophicly on 5 different organic compounds. Sodium acetate and glucose were found to be effective in supporting the growth. Sodium acetate...One isolate of Brachiomonas submarina was tested for its ability to grow heterotrophicly on 5 different organic compounds. Sodium acetate and glucose were found to be effective in supporting the growth. Sodium acetate was chosen as the organic nutrient to test the combined effects of organic and inorganic solutions on the growth and fatty acid composition of Brachiomonas submarina. The best growth rates were achieved at 3 mmol L -1 CH 3COONa and 0.88 mmol L -1 NaNO 3 in heterotrophic condition, and 4 mmol L -1 CH 3COONa and 3.52 mmol L -1 NaNO 3 in mixotrophic condition. The differences between fatty acid contents were significant. The total polyunsaturated fatty acids (T.P.U.F.As) varied from 55.79% to 67.72% in heteritrophic growth and from 52.39% to 65.55% in mixotrophic growth. It is concluded that CH 3COONa and NaNO 3 at 3 mmol L -1 and 3.52 mmol L -1 should respectively be used in order to achieve the highest growth rate and fatty acid content.展开更多
A unicellular-colonial cyanobacterium,designated“BRSZ,”was isolated from a neutral-alkaline hot spring in Thai-land.Morphological characterization revealed distinctive features consistent with those of the genus Glo...A unicellular-colonial cyanobacterium,designated“BRSZ,”was isolated from a neutral-alkaline hot spring in Thai-land.Morphological characterization revealed distinctive features consistent with those of the genus Gloeocapsa.Physiological assessments demonstrated that BRSZ is a moderately thermophilic and halotolerant cyanobacterium with the potential for chemoheterotrophic growth in dark conditions.Molecular phylogenetic analysis based on 16S ribosomal RNA(rRNA)gene sequences placed BRSZ within a well-defined Gloeocapsa clade,a finding cor-roborated by 16S-23S internal transcribed spacer(ITS)rRNA secondary structure analyses.Genome compar-isons,including average nucleotide identity(ANI),genome-to-genome distance(GGD),and digital DNA-DNA hybridization(dDDH),between strain BRSZ and closely related taxa showed an ANI value of 95.45%,near the lower boundary of the species delineation threshold(95-96%).A GGD of 0.0374(>0.0258)and dDDH of 69%(<70%)further supported genomic differentiation.Genome-based analysis revealed a mycosporine-like amino acid biosynthetic gene cluster likely involved in sunscreen compound production.Cultivation-based production of a UV-absorbing compound confirmed the functional relevance of this gene cluster.These findings expand the described diversity within the Gloeocapsa complex and enhance our understanding of the taxonomy of this group.In addition,they underscored the importance of hot spring environments as sources of novel extremophiles.展开更多
基金supported by the National Key Research and Development Program of China(2022YFF0802202)the Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources of China(no.2019017)+2 种基金the Shenzhen Science and Technology Program(grant number KCXFZ20211020165547011)the National Natural Science Foundation of China(no.42376110,41976127)the Fujian Provincial Natural Science Funds for Distinguished Young Scholar(2023J06043)
文摘Climate change may threaten the survival of corals due to ocean warming and increased occurrence of extreme weather events.Yet,marginal coral communities demonstrate remarkable adaptability,largely due to stress-tolerant species.The mechanisms underlying their resilience to environmental fluctuations remains largely unexplored.Here,we investigated 3 coral species(Cyphastrea serailia,Dipsastraea speciosa,and Duncanopsammia peltata)living at the northern edge of their distribution along the South China coast(Dongshan).Combining physiological and stable isotope analysis,we assessed their traits(symbiont characteristics,C:N ratio,and biomass)and trophic flexibility(i.e.,shifts in isotopic niche or nutritional mode)in response to environmental fluctuations across seasons(autumn,winter,and late spring).Our results revealed distinct physiological traits among these corals,but consistently showed lower symbiont density,higher biomass,and increased chlorophyll content in winter.All corals highly relied on heterotrophy as a crucial adaptive response(consistently no overlap between host and symbiont isotopic niches),but they differed in the degree of trophic plasticity,with D.speciosa showing the highest variability in heterotrophic contribution(36.3%across seasons),followed by C.serailia(21.8%)and D.peltata(8.6%).Notably,the species-specific differences in trophic plasticity well corresponded to the variation in overall isotopic niche and coral distribution.As such,trophic plasticity may play a role in shaping spatial distribution of corals in the marginal community.Overall,this study enhances our understanding of coral resilience in marginal communities and offer new insights into possible mechanisms driving the distribution of reef-building corals in the changing ocean.
文摘The effects of several nutritional factors on the growth and eicosapentaenoic acid （EPA） production of diatom Nitzschia laevis were studied. 4LDM （quadrupled concentration of the nutrient salt） was the optimal concentration of nutrient salt for the growth and EPA production ofN. laevis. The growth ofN. laevis was inhibited when the glucose concentration was either lower than 10gL^-1 or higher than 15 gL^-1. Both sodium nitrate and urea were good nitrogen sources for the growth and EPA production, while ammonium chloride seriously decreased the dry cell weight （DW） and the EPA content. Silicate seriously influenced the growth of N. laevis. The maximum DW of 2.34 gL^-1 was obtained in the presence of 150 mgL^-1 Na2SiO3· 9H2O. The EPA content remained almost the same when the silicate concentration was lower than 150mgL^-1; however, higher silicate concentrations resulted in a steady decrease of EPA content. Low medium salinity （≤29） did not seem to influence the DW of N. laevis, and high salinity resulted in a decrease of DW. The highest EPA content （4.08%） and yield （110mgL^-1） were observed at the salinity of 36 and 29, respectively. Key words polyunsaturated fatty acid; eicosapentaenoic acid; microalga; Nitzschia laevis; heterotrophy
文摘One isolate of Brachiomonas submarina was tested for its ability to grow heterotrophicly on 5 different organic compounds. Sodium acetate and glucose were found to be effective in supporting the growth. Sodium acetate was chosen as the organic nutrient to test the combined effects of organic and inorganic solutions on the growth and fatty acid composition of Brachiomonas submarina. The best growth rates were achieved at 3 mmol L -1 CH 3COONa and 0.88 mmol L -1 NaNO 3 in heterotrophic condition, and 4 mmol L -1 CH 3COONa and 3.52 mmol L -1 NaNO 3 in mixotrophic condition. The differences between fatty acid contents were significant. The total polyunsaturated fatty acids (T.P.U.F.As) varied from 55.79% to 67.72% in heteritrophic growth and from 52.39% to 65.55% in mixotrophic growth. It is concluded that CH 3COONa and NaNO 3 at 3 mmol L -1 and 3.52 mmol L -1 should respectively be used in order to achieve the highest growth rate and fatty acid content.
基金supported in part by the following research grants:Thai-land Science research and Innovation fund Chulalongkorn University(FOOD_FF_68_121_2300_022)(to RWS)the Singapore Ministry of Ed-ucation MOE-T2EP30123-0007(to RWS&SBP)+1 种基金the Research Institute of Meijo University(to HK)Postdoctoral Fellowship,the Second Century Fund(C2F),Chulalongkorn University(to SS).
文摘A unicellular-colonial cyanobacterium,designated“BRSZ,”was isolated from a neutral-alkaline hot spring in Thai-land.Morphological characterization revealed distinctive features consistent with those of the genus Gloeocapsa.Physiological assessments demonstrated that BRSZ is a moderately thermophilic and halotolerant cyanobacterium with the potential for chemoheterotrophic growth in dark conditions.Molecular phylogenetic analysis based on 16S ribosomal RNA(rRNA)gene sequences placed BRSZ within a well-defined Gloeocapsa clade,a finding cor-roborated by 16S-23S internal transcribed spacer(ITS)rRNA secondary structure analyses.Genome compar-isons,including average nucleotide identity(ANI),genome-to-genome distance(GGD),and digital DNA-DNA hybridization(dDDH),between strain BRSZ and closely related taxa showed an ANI value of 95.45%,near the lower boundary of the species delineation threshold(95-96%).A GGD of 0.0374(>0.0258)and dDDH of 69%(<70%)further supported genomic differentiation.Genome-based analysis revealed a mycosporine-like amino acid biosynthetic gene cluster likely involved in sunscreen compound production.Cultivation-based production of a UV-absorbing compound confirmed the functional relevance of this gene cluster.These findings expand the described diversity within the Gloeocapsa complex and enhance our understanding of the taxonomy of this group.In addition,they underscored the importance of hot spring environments as sources of novel extremophiles.
