Studies on diversity of culturable bacteria in karst cave soil of Xingyi, Guizhou and their protease and amylase activities

Abstract:

[Objective] The main focus for the current study is to investigate the diversity of culturable bacteria in soils of karst caves located in Xingyi county of Guizhou province and to analyze their potential for production of protease and amylase. [Methods] Isolation of the culturable bacteria was done by spread plate technique using 11 synthetic media. Phylogenetic relationship of the isolates based on their 16S rRNA gene sequences was analyzed. The isolates were then screened for production of protease and amylase using plate method. [Results] Based on the 16S rRNA gene sequences, a total of 217 isolates affiliated to 63 species of 24 genera were determined, of which the genera Rhodococcus and Streptomyces were the dominant bacteria (comprising 24.42% and 21.66% respectively). Majority of these strains had 16S rRNA gene sequence similarities ranging between 97.90% and 99.99% with related type strains, except the strains D3T01, D911, D961 and D502 which are potential new taxa. Of these culturable bacteria isolated, 99 strains belonging to 38 species of 18 genera were positive for protease and/or amylase activities. Among these, 36 strains had both amylase and protease activities, thus constituting about 36.36% of the bioactive strains and 16.59% of the total isolates. [Conclusion] The results indicated that soil of karst caves in southwest of Guizhou are promising sources for isolation of many bioactive strains, with potential for further exploration and research.