Diversity,Isolation Of Microorganisms In Lake Sediments And Taxonomic Analysis Of Four Novel Bacteria

Lakes are an important part of the global aquatic ecosystem.In the lake ecosystem,sediment is the carrier for the circulation and exchange of nutrients between microorganisms and lake ecological environment.Microorganisms are the main driving force of natural material cycle.Therefore,knowing the diversity of microorganisms in lake sediments can lay the foundation for understanding the biochemical cycles of the earth and the functions of lake ecosystems.There are a lot of researches on the microbial community structure of lakes in China,but there is a lack of systematic analysis on the microbial diversity of sediments in lakes.Secondly,as the second largest drug source microorganisms,myxobacteria have great application potential in agriculture,bio-medicine and environmental protection.This study is based on culture-dependent and culture-independent approaches,and to expand microbial germplasm resources(focusing on the isolation and culture of myxobatera resources),analysis of the domestic part of lake sediments of bacterial community composition and diversity.Bacterial diversity and community composition of lake sediments in China were analyzed by second-generation high-throughput sequencing technology.The results showed that the lake sediments of Qinghai-Tibet lake and Inner Mongolia-Xinjiang lakes were generally high in salt and alkali,and the diversity and richness of bacteria detected in the lakes were very low.At the same time,the species composition of different lakes varied greatly.For example,the relative abundance of Campylobacterials in Erhai lake,Fuxian lake,Ma lake and Zibi lake is more than 20%,but it is almost not detected in the sediment of Chenghai Lake.Halanaerobiaeota occupied a large proportion in Ebi lake(27.0%)and Balikun lake(26.8%),but their relative abundance in other lakes were low.Firmicutes accounted for 5.1%,2.3%and 10.4%in Nierco lake,Humaco lake and Zhouzipao lake,respectively.But no large proportionof Firmicutes sequences were found in other lakes.Subsequently,we picked up the sequence of myxobacteria and analyzed the abundance of myxobacteria in different samples at the order and genus levels.The results showed that the myxobacteria were more likely to survive in the low saline-alkali environment,and Anaeromyxobacter was widely distributed in the lake sediments and had high abundance,which was the dominant group in the lake sediments.We also used Mantel Test to analyze the environmental factors affecting species composition.The results of null model analysis also verified the above conclusions,geographical factors had a greater influence than environmental factors,and the composition of bacterial community in lake sediments was mainly affected by diffusion limitation.However,up to now,the function and metabolism of microbial community can not be resolved by omics analysis,and pure culture isolation technology still occupies a very important position.We can test a variety of physiological and biochemical traits of the microorganisms by pure culturing,which not only improves the reproducibility of the experiment and the reliability of statistics,but also helps the omics research to verify the predicted ecological function and metabolism.Therefore,we enriched and isolated the bacteria in these lakes,and focused on isolating and cultivating the resources of myxobacteria in the lake sediment of the eastern and northeastern lakes.Three species of Myxococcus were isolated from Jingpo lake.In addition,we also isolated a new genus of Flavobacteriaceae fiom the sediments of Chaiwopu lake,which shows the characteristics of halophilic and addicted to low temperature.Two new strains were isolated from the soil of wetland of the Yellow River Delta.One was a new species of Psychroflexus and the other was a new genus of Balneolaceae.In this paper,multiphase classification studies including phylogenetics,genomics,morphological,physiological and biochemical characteristics and chemical composition characteristics of four new strains were studied.Strain JPH2T is presented as a representative of a new species of Corallococcus,for which the name Corallococcus viridans sp.nov)is proposed.Strain CWB-11 represents a novel genus of the family Flavobacteriaceae,for which the name Paucihalobacter ruber gen.nov.sp.nov.is proposed.Strain YR1-1T represeIts a new species of the genus Psychroflexus,for which the name Psychroflexus aurantiacus sp.nov.is proposed.Strain YR4-1T represents a novel genus of the family Balneolaceae,for which the name Halalkalibacterium roseum gen.nov.sp.nov.is proposed.We also preliminarily excavated their genomic informations and predicted their gene functions while identifying the new bacteria,which laid a good foundation for the future study of the structure,function and new metabolic pathways of lake microorganisms.