Isolation, molecular identification and characterization of boron-tolerant bacterial strains from sewage treatment pond of Islamabad, Pakistan

Abstract

Boron-tolerant bacteria fall in the category of extremophilic organisms as they have the ability to survive in high boron environments. Such bacterial species needs to be characterized to identify new extremophilic organisms from the ecology for biotechnological benefits. In this study, five boron-tolerant bacterial strains, designated as NCCP-132, NCCP-133, NCCP-134, NCCP-135 and NCCP-136 were isolated from sewage sludge treatment pond of Islamabad, Pakistan. These strains grew on media containing 200 to more than 450 mM of boron concentration. However, the microbial growth is found high at low boron concentration. The isolated boron-tolerant bacterial strains were either extremely boron-tolerant or moderately boron-tolerant. The 16S rRNA gene sequences and phylogenetic analyses delineated that all strains were found to be closely related to species belonging to different genera:Bacillus, Oceanobacillus and Lentibacillus. Strains NCCP-132, NCCP-134 and NCCP-135 are found to be novel species, while NCCP-133 and NCCP-136 are revealed to be previously identified bacterial species. Morphological, physiological and biochemical characteristics of these strains were studied at their optimal growth conditions. Our study inferred that the sewage treatment pond of Islamabad, Pakistan is rich in boron-tolerant extremophilic bacterial population with diverse bacterial communities having a potential to be utilized in various biotechnological applications in future.

Keywords: Boron, 16S rRNA, Phylogeny, Bacillus, Lentibacillus, Oceanobacillus