Halophilic Bacteria Diversity In Yuncheng Salt Lake And Their Ability To Produce Enzymes

Yuncheng Salt Lake is an ancient and typical inland saltwater lake,rich in mirabilite(maincomponent is sodium sulfate)and it isan idealobject to study thediversityofhalophilicbacteria.Halophilic bacteria area kind of microbial resources with basic research value and application prospects.By virtue ofits special physiological structure,metabolic mechanism,population groups,genetic and unique metabolites,they havereceived extensive attention of scholars at home and abroad.In this study,we combined cultivation approach and culture-independent techniqueto explore the diversity of halophilic bacteria of Yuncheng Salt Lake.We also carried out the identificationof novel candidates by polyphasic approach,and screened potential strains for cellulase and xylanase activities.Biolog ECO method isa quantitative analysis,based on the carbon sources utilization in MicroWell plate,which can describe the metabolic characteristics of microbial community simply and quickly.The diversity and metabolic characteristics of ten representative samples of Yuncheng Salt Lake were studied by AWCD curve,substrate metabolic difference,diversity index and principal component analysis.The results showed that ten microbial communities in Yuncheng Salt Lake could be divided into three metabolic types.Also we predicted "effective separation of the substrate type" for the separation of environmental microbes in Yuncheng Salt Lake: one wasseparation medium rich in sugar and esters and the other one wasrich in amino acids and amine.The diversity of halophilic bacteria in Yuncheng Salt Lake was analyzed by high-throughput sequencingtechnique.Of the total 24 samples,705,689 original sequences were obtained,16,877 OTU were annotated and the average length was about 396 bp.The results showed that there were 30 phylathrough the analysis of the QIIME platform which mainly includes: Firmicutes(47.6%),Proteobacteria(35.6%),Bacteroidetes(3.7%),Actinobacteria(3.6%)and Bacteria Other(2.9%).PCoA and CCA analyses showed that the halophilic bacteria in these24 samples can be divided into three groups,for which Ca2+ and Fe2+ were the main chemical factors affecting the microbial community.After comparing with the changes of bacteria community composition of different salt concentrations in the same salt lake,we found that the community composition of the halophilic bacteria in two samples near the salt lake center were similar,while the composition of the halophilic bacteria community in the two spots from the salt lake center were similar.At the same time,a large number of classic halophilic groups,extreme microbial groups and microbial taxonomic information with specific functions were also detected in Yuncheng Salt Lake.Based on the metabolic characteristics and physicochemical parameters of the integrated bacterial community,five classes of ten isolation media were designed for isolation of halophilic bacteria from ten samplesof Yuncheng Salt Lake.The results showed that a total of 1,033 halophilic bacteria were isolated,after removing the similar strains,and 605 halophilic bacteria were sequenced.After identification,the strains were belonging to Actinobacteria,Firmicutes,Proteobacteria and Bacteroidetes,comprising7 classes,18 orders,41 families,82 genera and 52 potential novel taxa.The present study also showed that the nutrient composition,the concentration of added salt and the different samples had significant effects on the isolation of these bacteria.Based on the studies of morphological,physiological and biochemical characteristics,chemical composition and phylogenetic analysis,the two new species(Halomonas halodurans sp.nov.,and Paracoccus halotolerans sp.nov.)wereidentifiedby polyphasic taxonomy method.We determined the classification status of the two candidates for the new species.Cellulose and hemicellulose are renewable resources on the planet that are producing in huge amount butnot fully utilized.The cellulase and xylanase activitiesof 1,033 halophilic bacteria strains were screenedby Congo red staining method and 32 strains with cellulase activity and49 strains with xylanase activity were found.The positive rate was 3.1% and 4.7%,respectively,of which 12 strains hadboth cellulase and xylanaseactivities.The addition of a functional substrate to the isolation medium could increase the availability of functional strains.The implementation of this study could explorethe metabolic characteristics and community diversity of halophilic bacteria in Yuncheng Salt Lake,and strengthen the excavation,development and utilization of halophilic bacteria and functional strains with salt-stable enzymes in salt lake habitat.