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 degrees C 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 alpha, beta and gamma 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.