Abstract
BackgroundA geothermal ecosystem located at Tantloi, India has been found to be an interesting habitat for microbes of diverse nature. However, the microbial diversity of this habitat is poorly explored. In this study, a detailed phylogenetic study has been carried out to understand the bacterial diversity of this habitat and to identify prospective metal reducers using culture independent approach. The bacterial diversity of the sediments, which contain undetectable levels of Cr(VI), was analysed with respect to chromium reduction and the strains highly resistant to and efficiently reducing chromium under aerobic conditions were isolated and characterized.Results16S rRNA gene sequence analysis of Tantloi hot spring microbial community revealed a significant bacterial diversity represented by at least ten taxonomic divisions of Bacteria with clear predominance of Thermus. Similar sequence analysis of rRNA gene library clones derived from bacterial consortia enriched from sediments in presence of Cr(VI) revealed the abundance of the family Bacillaceae. Under aerobic conditions at 65°C, the consortia reduced 1 mM of Cr(VI) completely within 24 h and 5 mM in 6 days. A complete reduction of 1 mM Cr(VI) has been shown by five of our isolates within 36 h. 16S rRNA gene sequences of all the isolates showed high degree of similarity (97-99%) to Bacillaceae with ten of them being affiliated to Anoxybacillus. Crude extract as well as the soluble fraction from isolates TSB-1 and TSB-9 readily reduced Cr(VI); TSB-1 showed higher chromium reductase activity.ConclusionMost of the Tantloi Spring Bacterial (TSB) sequences analyzed in different taxonomic divisions could be related to representatives with known metabolic traits which indicated presence of organisms involved in redox processes of a variety of elements including iron, sulphur and chromium. Approximately 80% of the sequences obtained in this study represented novel phylotypes indicating the possibility of discovery of bacteria with biotechnologically important new biomolecules. Again, highly chromium-resistant and remarkably active Cr(VI)-reducing Anoxybacillus strains isolated in this study could serve as potential candidates for designing chromium bioremediation strategies at high temperatures and also at high chromium concentrations.
Highlights
A geothermal ecosystem located at Tantloi, India has been found to be an interesting habitat for microbes of diverse nature
We aimed to explore the bacterial community present in Tantloi hot spring to gain knowledge about nature and possible roles of microorganisms present therein with respect to redox phenomena
In this study, 16S rRNA gene clone library based analysis was performed to understand the bacterial diversity present in a hot spring in Tantloi, India. No, such detailed phylogenetic analysis of the bacterial community is yet reported from this hot spring ecosystem
Summary
A geothermal ecosystem located at Tantloi, India has been found to be an interesting habitat for microbes of diverse nature. Only sporadic attempts have been made to isolate thermophiles and understand ecological roles, diversity and biotechnological applications of microorganisms from thermal ecosystems of India using culture independent approaches [8,9]. Whereas cultivation-dependent studies are valuable for isolating novel organisms and exploring their properties; the cultivation independent methods offer a more comprehensive assessment of microbial diversity [4,10,11]. Both the sediment and the soil probably represent some of the most complex microbial habitats on the earth. There may be several thousand species of bacteria in 1 g of soil [3,12] which can be studied using various approaches to understand the genetic diversity of microbial populations of different microbial habitats [13]
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