Characterization and Identification of Naphthalene Degrading Bacteria Isolated from Petroleum Contaminated Sites and Their Possible Use in Bioremediation

Naphthalene is a simple polycyclic aromatic hydrocarbon (PAH) regarded as a common environmental pollutant. A total number of 16 bacterial isolates obtained from various petroleum contaminated sites of Gwalior (MP), India were screened for their naphthalene degradation potential. Enrichment method was used for the isolation of bacteria by amending the medium with 100 mg l(-1) naphthalene dissolved in acetone. Out of 16 bacterial isolates, only two isolates designated as RS2(3) and GS2 have shown a good naphthalene degradation potential based on maximum tolerance level at 1000 mg l(-1) and growth of the isolates as 0.536 and 0.133, respectively measured in terms of optical density (OD) at 600 nm. The degradation was determined by GC analysis, GS2 showed 73% and 48% degradation, while RS2(3) showed 52% and 29% at 100 and 200 mg l(-1) naphthalene concentration, respectively. The isolates were also characterized for their heavy metal tolerance against four selected heavy metals (Cadmium, Chromium, Copper and Zinc) at different concentrations (0.1%, 0.5% and 1.0%). Out of total 16 bacterial isolates only twelve were found resistant to one percent concentration of any one of the four heavy metals. Moreover, the antibiotic sensitivity of the isolates was also determined against four different antibiotics. These isolates were characterized morphologically, biochemically and identified as strain Bacillus licheniformis JUG GS2 (MK106145) and Bacillus sonorensis JUG (RS2(3)) (MK156710) by 16S rRNA gene sequencing. The study infers that Bacillus licheniformis and Bacillus sonorensis strains can be helpful to remediate contaminations attributed to naphthalene and heavy metals as well.