Diversity And Biological Characteristics Of Actinomycete Actinomycetes Geodermatophila, Which Are Characteristic Of Desert Environments

The desert environment is characterized by oligotrophic,extreme drought,strong solar radiation,and huge temperature fluctuations between day and night.These severe environmental pressures are not only a challenge to life,but also a driving force for life evolution.As a kind of gram-staining-positive bacteria with high GC content,members of the family Geodermatophilaceae are regarded as pioneer organisms in the desert environment.Under the stress of desert environment,the strains of Geodermatophilaceae may have evolved into some unique adaptive mechanisms.For a long time,due to the restriction of microbial cultivation techniques,insufficient pure cultures of the family Geodermatophilaceae have been collected for systematic research,so that the research on the family Geodermatophilaceae has been limited to the observation on the sporadic strainsIn this study,we collected desert soil samples from different ecological environments from two typical deserts in China,Badain Jaran desert and Gurbantunggut Desert.Firstly,the high-throughput sequencing method was used to detect the microbial diversity and abundance in different micro-environments.The microbial community structure characteristics were analyzed by construction of co-occurrence network map,focusing on detection of the distribution properties of the family Geodermatophilaceae in the desert environment,based on which optimized the isolation methods on microbial pure cultures,to collect Geodermatophilaceae strains.Subsequently,the phenotypic characteristics of Geodermatophilaceae strains were collected using the Biolog phenotype microarrays experiments.The 44 soil samples collected from Gurbantunggut Desert were pooled into 8 groups according to micro-environments,and high-throughput sequencing analysis was performed.After splicings,389,321 reads were obtained.Usearch was used to perform OTU clustering analysis of sequences,and a total of microbial groups belonging to of 575 genera of 27 phyla were detected.There were 6494 reads,accounting for 1.67%,belonging to the family Geodermatophilaceae.As a result,members of the family Geodermatophilaceae were detected in 8 different micro-environments.The co-occurrence network based on high-throughput sequencing analysis indicated that the actinomycetes of the family Geodermatophilaceae were the core flora and the specific microbial group in the desert environment.The interaction between the family Geodermatophilaceae and other core bacteria in the desert environment is complex Members of the family Geodermatophilaceae may play a positive role in the colonization of some other microorganismsAccording to the results of high-throughput sequencing we selected,40 samples from Badain Jaran desert and 44 samples from Gurbantunggut Desert for microbe isolation by pure culture method.As a result,505 strains belonging to 90 genera of 5 phylum in bacterial domain were isolated and purified from badan Jaran desert,and 361 strains belonging to 76 genera of 3 phylum in bacterial domain were isolated from Gurbantunggut Desert.Among them,16 strains of the family Geodermatophilaceae were obtained from 84 desert samplesPhenotypic microarray test results showed that:1)The carbon source utilization spectrum of the family Geodermatophilaceae was wide.All of the tested strains from desert environment could assimilate polysaccharides(dextrin),91.7%of the tested strains were able to assimilate acetic acid and 75%of strains could assimilate ester compounds such as Tween 40.Among the 71 carbon sources tested,only 3-methyl-glucose,D-melibiose,D-saccharic acid,L-alanine,L-histidine and β-methyl-D-glucoside were not utilized by any of the strains.The correlation between the strains’ assimilation of carbon sources and their taxonomic status of strains was more obvious than that with the corresponding ecology.2)In terms of assimilation of nitrogen source,phosphorus source and sulfur source,the family Geodermatophilaceae showed no obvious correlation between the assimilation of with the ecological environment and taxonomic status of the strain.The taxonomic status of strains CPCC 205119T,CPCC 205215 and CPCC 205251 collected from desert were comfirmed by combining the phenotype and genotype characteristics.These three strains represent a new species of the genus Modestobacter,which is named as Modestobacter deserti,with strain CPCC 205119T as the typical strain.In this study,we systematically analyzed the diversity of Geodermatophilaceae in the desert environment,collected the biological characteristics of strains in the family Geodermatophilaceae,and preliminarily analyzed the genetic basis of the tress resistance characteristics of strains in the family Geodermatophilaceae from the level of genome.