Biochemical, molecular and antibiotic resistance profile of multi-potential toluene metabolizing bacteria isolated from tannery effluents

The focus of present study was to isolate and characterize bacteria which can be effectively used for toluene, a highly recalcitrant pollutant, bioremediation. For isolation of bacteria from the tannery effluents selective enrichment and serial dilution methods were employed. The isolated bacteria were subjected to growth curve analysis, estimation of toluene removal efficiencies, biochemical tests, antibiotic sensitivity assays and molecular characterization based upon 16S rRNA gene. The rRNA genes sequences were analyzed through BLAST to determine similarity index of isolates with bacterial database sequences. To trace the evolutionary history, phylogenetic trees were constructed using MEGA version 7. Total twenty toluene metabolizing bacteria (IUBT1-2, 4-12, 16, 19, 21, 23-26, 28 and 30) were isolated and characterized. Their rRNA gene sequences have been submitted to Genbank. Fifteen of the twenty isolates showed homology to Brevibacillus agri strain NBRC 15538, four found similar to Bacillus paralicheniformis strain KJ-16 and one homologous to Burkholderia lata strain 383. All bacterial isolates were resistant to chloramphenicol but sensitive to teicoplanin and linezolid. However, few (i. e.; IUBT9 and 26) were sensitive to oxacillin. Biochemical characterization indicated all bacteria positive for alkaline phosphatases (100%). While many were found positive for p-nitrophenyl N-acetyl {beta}, D-glucosaminidase (35%), hydroxyproline {beta}-naphthylaminopeptidase (15%), esculinase (65%), mannitol (75%), sorbitol (95%) and inulin (90%) fermentation. Biochemical profile suggests the use of isolated bacteria for future exploitation in several fields like bioremediation of toluene, ethanol production, biomass hydrolysis, biosensors, biofertilizers, as a marker for milk pasteurization in dairy industries and evaluation of soil quality.\n\nImportanceToluene is a highly toxic environmental pollutant. We have isolated bacteria which can be effectively used for the removal of toluene from environmental resources. Moreover, these bacteria are capable to produce many valuable enzymes which can be used in many industrial processes for the production of a wide range of products. Further study may help to exploit these bacterial for the benefit of humanity.