| The ocean occupies approximately 71%of the earth's surface area,and it is an open,changeable,and complex ecosystem.There are a large number of microbial resources in the ocean.The complexity of the marine environment makes the microorganisms in the ocean diverse and specific in terms of genetics and metabolism.Microbes participate in the entire process of the decomposition and transformation of marine materials,and provide rich resources for human beings.Microbes are a very important part of the ocean and have great significance to research.Peptidoglycan is a unique and necessary structural component in bacterial cell walls.The function of peptidoglycan is to maintain cell integrity and maintain bacterial shape.The research on the ultrastructure and chemical structure of peptidoglycan is of great significance to the life activities of bacteria.At present,there are few studies on the ultrastructure of cell wall peptidoglycan,especially the diversity of peptidoglycan ultrastructure and the influence of different growth conditions on the peptidoglycan ultrastructure are not clear.Atomic force microscopy is a powerful microscopy technique that can directly study biological samples with high resolution without staining the samples.It is very suitable for studying the ultrastructure of bacterial cell wall peptidoglycans.In this paper,we identified a bacterium which isolated from the surface seawater near the Great Wall Station in Antarctic by polyphasic taxonomic method.Firstly,the taxonomic status of the strain has been determined.Next,the peptidoglycan of B.safensis SDMCC 050126 in diverse growth conditions has been studied with AFM.Finally,the peptidoglycan of four Bacillus strains have been extracted and observed using AFM.Our results showed that the diversity and variation of peptidoglycan from different bacteria in the same genus.The concrete results are as follows.1.Study on the polyphasic taxonomic of strain SM1703TThe Antarctic region,where the environment is greatly extreme,contains ample microbial resources.Strain SM1703T isolated from the surface seawater near the Great Wall Station in Antarctic by our group.Cells of the strain SM1703T are Gram-stain-negative,aerobic,non-flagellated,rod-shaped bacterium.Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1703T formed a distinct phylogenetic lineage within the family 'Rhodobacteraceae',sharing high 16S rRNA gene sequence similarity with Marivita litorea(95.5%).The strain grew at 10-37?(optimum,25?),with 0.5-13%(w/v)NaCl(optimum,3-5%)and at pH 6.0-10.0(optimum at pH 7.5).The major cellular fatty acids were C19:0 cyclo ?8c(36.1%),C18:1 ?7c(32.6%),C18:1 2-OH(7.1%)and C16:0 2-OH(6.7%).The major polar lipids were phosphatidylglycerol,phosphatidylcholine,an unidentified aminolipid and an unidentified lipid.The genomic DNA G+C content of strain SM1703T was 64.6 mol%.Based on the results of the polyphasic characterization for strain SM1703T,it is classified as the representative of a novel species in a new genus of the family 'Rhodobacteraceae',for which the name Chachezhania antarctica gen.nov.,sp.nov.is proposed.The type strain of Chachezhania antarctica is SM1703T(=MCCC 1K03470T=KCTC 62794T=CCTCC AB 2018351T).After the research on the polyphasic taxonomic of strain SM1703T,we have a fresh cognition of Rhodobacteraceae.Meanwhile,it provides the basis for the development and utilization of marine resources.2.Effect of growth conditions on the peptidoglycan from B.safensis SDMCC 050126In order to elucidate the influence of culture temperature,growth period and teichoic acids on the ultrastructure of peptidoglycan in B.safensis SDMCC 050126.The cells were cultured at 15? and 37?,when cells grew to mid-log and stable phase,the cell wall were extracted to study.Furthermore,samples were handled with HF or not.Finally,the samples were observed by AFM.The results showed that the peptidoglycan of B.safensis SDMCC 050126 has significant gully structure,and the gully structure on the surface of the peptidoglycan in logarithmic metaphase is more than that in stationary phase.When the temperature is 37?,the gully structure on the surface of the peptidoglycan is more conspicuous than when the temperature is 15?.The gully structure is not related to teichoic acids.The results lay a structural foundation for elucidating the relationship between the ultrastructure and chemical components of cell wall peptidoglycan in B.safensis SDMCC 050126.3.Research on the diverse of peptidoglycan in BacillusBased on the detailed study on the ultrastructure and variation of peptidoglycan in B.safensis SDMCC 050126,we obtained the fine structure of peptidoglycan in B.siamensis SDMCC 050135,B.subtilis SDMCC 050117,B.albus SDMCC 080146 and B.tequilensis SDMCC 080100 to reveal the diversity and variation of peptidoglycan from different bacteria in the same genus.The results showed that,the peptidoglycan of B.siamensis SDMCC 050135 has obvious gully structure,and the ultrastructure of peptidoglycan changes with different growth conditions,varying from gully structure in logarithmic period to mesh shape and coiled-cable structure in stable period.The peptidoglycan of B.tequilensis SDMCC 080100 changes to mesh shape and coiled-cable when the growth conditions changed.The surface of peptidoglycan of B.subtilis SDMCC 050117 is relatively smooth and flat,the arrangement of peptidoglycan is extremely compact.The inner side of the peptidoglycan is slightly rougher than the outer side.The inner side of peptidoglycan of B.albus SDMCC 080146 is relatively dense with shallow groove structure.The study on the ultrastructure of peptidoglycan in Bacillus has given us a deeper understanding of the structural diversity of microbial cell walls at the nanoscale. |
PDF Full Text Request