Phylogenetic Characterization of BKH3 Bacterium Isolated from a Hot Spring Consortium of Bakreshwar (India) and Its Application

Abstract

Background: The silica leaching attribute of some of the mystifying bacteria present in the cluster of hot springs (temperatures range 35 °C - 80 °C ) at Bakreshwar (West Bengal, India, 23 ° 52'48"N; 87 ° 22'40") has provided some significant advancements in construction technology when incorporated to the concrete/mortar specimens. The present investigation was designed to isolate other novel bacterial strains from 65 °C hot spring that could have similar or better performance in construction technology. Methods: Soil sample collected from the 65 °C hot spring was inoculated to the culture vials (incubated at 65 °C ) containing a specific synthetic growth medium (pH 8.0) to grow the bacterial population anaerobically by degassing the medium with CO 2 gas. Subsequent serial dilution techniques were employed to isolate pure culture of a specific bacterial strain. 16S rRNA gene sequence and phylogenetic analysis was carried out to identify the novelty of the isolated bacterial strain. The isolated bacteria were incorporated to the cement sand mixture at various cell concentrations to evaluate the efficacy of the strain in construction technology. Results: The work revealed the presence of a novel bacterial strain (BKH3; GenBank Accession No.: KP 890928) within the same hot spring consortium whose 16S rRNA gene sequence data showed 96% identity with Citrobacter freundii bacterial species. The newly isolated bacteria when incorporated at different cell concentration to the cement/cement-sand mixture were found to possess the similar compressive strength increment property, the cracks repairing ability and the water ingression resistivity. It also reduced the permeability of sulphate ions to the cementitious matrix reflecting the increment of durability of the incorporated material. Conclusions: The enhancement of compressive strength and durability of the as prepared bio-concrete material by using the isolated bacterial strain (BKH3) was due to the silica leaching activity of the bioremediase like protein secreted by the bacterium. This may open up another vista of utilization of hot spring bacterium for beneficial purposes in construction technology.