Phylogenetic and physiological diversity of cold-adapted bacteria producing protease from sediments of the bottom layer of the Glacier No． 1 in the Tianshan Mountains

Abstract:

Abstract:［Objective］We characterized proteolytic bacteria isolates from sediments of the bottom layer of the Glacier No．1 in the Tianshan Mountains，China．Physiological test and phylogenetic analysis were undertaken to expand our knowledge on diversity and ecological distribution of psycrotrophic and psycrophlic bacteria populations．［Methods］Using the screening media containing skim milk，we screened cold-adapted strains producing protease． Taxonomic identity and genetic variability of strains isolated was determined by partial 16S rRNA gene sequences and repetitive-element PCR fingerprint．［Results］Of the total 125 cold-adapted bacterial isolates，high levels of protease activity were observed from 27 isolates at optimal growth temperatures ranging from 15 to 24℃ in plate assay． Among 27 protease-producing strains， only 6 isolates were psychrophilic．The 16S rRNA gene phylogenetic analysis revealed that protease-producing isolates belonged to 5 phyum，namely α、，β and !of Proteobacteria，Actinobacteria and Cytophaga-Flexibacter-Bacteroides． They are affiliated to the genera Pseudomonas， Polaromonas，Brevundimonas， Rholococces，Cryobacterium， Kocuria，Arthrobacter，Chryseobacterium and Flavobacterium．The populations of the predominant cultivated protease-producing bacteria are the Pseudomonas spp．(40.7%)．［Conclusion］The results enriched our knowledge on the phylogenetic and physiological diversity of cold-adapted strains producing protease in cold environments．

Key words:Keywords: permafrost，Tianshan Mountains，bacterial phylogeny，cold-adapted protease