Polyphasic Taxonomy Of Microorganisms From Saline Environments And Genomic Adaptation And Evolution Of Haloarchaea

Due to the harsh climate and surrounding high mountains,the microbial resources have rarely been reported on the depopulated zone of Altun Mountain in Xinjiang.This study focuses on the high-altitude salt lakes of Altun Mountain in Xinjiang.The culture-independent method and the culture-dependent methods were used to analysis the microbial community structure of those salt lakes and explore the resources of halophiles.Six isolates were described using polyphasic taxonomic method.In addition,the genomes of 39 halophilic archaeal type strains were sequenced,and the environmental adaptation and genomic evolution of one of them were analyzed in depth.Culture-independent metagenomics method was used to study the microbial community structure of Ayaqqum lake and Manas lake.We found that in Ayakekumu Lake,bacteria are the dominant group,and the Rhodobacterales has the highest abundance at order level.However,halophilic archaea is the dominant group of Manas lake,and Halorubrum has the highest of abundance at genus level.403 halophiles were isolated and purified using culture-dependent method,including 191 halophilic archaea and 212 halophilic bacteria,of which 8 halophilic archaea were suspected as new taxa,and 17 halophilic bacteria were suspected new taxa.In the community analysis,the halophilic archaeal community structures were relatively similar between Manas lake and Yuncheng salt lake,Xiaokuer salt lake and Yuncheng salt lake.The bacterial community structures were similar among Kardun lake,Ayqqum lake and Longweicuo lake.Marinobacter was the dominant group of those three lakes.Whereas,previous studies demonstrated that most species of the genus Marinobacter were directly or indirectly isolated from the ocean.This new finding may provide a strong proof of the hypothesis that Qinghai-Tibet Plateau originated from the ocean.Polyphasic taxonomic study was conducted on 6 halophilic microorganisms isolated from different saline environments,and 2 new genera(Salilacivita gen.nov.and Ayaqqumibacter gen.nov.)and 6 new species(Salilacivita planktonica,Ayaqqumibacter halotolerans,Wenzhouxiangella salilacus,Rhodohalobacter barkolensis,Marinobacterium zhoushanense and Terasakiella brassicae)were established.This study enriched the resources of halophilic microorganisms at genus and species level and provide species materials and reference information for subsequent research.The genomes of 39 type strains of halophilic archaea were sequenced,and a total of 9 high-quality completed genomes and 30 draft genomes were obtained,which greatly enriched the genome data resources of halophilic archaea type strains.The environmental adaptation and genomic evolution of Salinigranum rubrum GX10~T were analyzed in depth.The genome of strain GX10~T consists of a circular chromosome and 5 circular plasmids.There is a great number of genes encoding K~+and Na~+transporters and genes related to the absorption and synthesis of compatible solutes in its genome,enabling it to maintain a balance of osmotic pressure inside and outside the cell.The acidic protein isoelectric point allows the biological macromolecules in the cell to maintain a stable structure in a high-salt environment.The strain has a complete DNA repair system such as light repair,excision repair,mismatch repair,and recombination repair,which can repair damaged DNA caused by UV radiation.The genome of this strain contains a great number of genes related to heavy metal resistance and metabolism,which may reduce the toxic effects of heavy metals on the cell.The genome contains multiple CRISPR sites and multiple types of Cas protein coding genes,which form the CRISPR-Cas system to degrade bacteriophages and foreign DNA invading cells and maintain the stability of the genome.We used the phylogenetic-tree-based method to annotate new genes of this strain and found that most of the new genes were formed in species differentiation of the Thermoplasmata and Halobacteria.Taken together,this study revealed the microbial community and the unique community types of Altun Mountain salt lakes and deepened the understanding of microbial distribution in special environments.A polyphasic taxonomic study was conducted on 6 suspected new taxa,which enriched the resources of halophilic microorganisms.Whole genome sequencing of 39halophilic archaeal type strains was performed,laying a data foundation for subsequent taxonomy,comparative genomic and biotechnology utilization.The environmental adaptation and genetic evolution analysis of the strain GX10~T further deepen the understanding of the survival strategy and evolution history of life in extreme environments.