Utilization of endophytic strain Bacillus sp. SBER3 for biodegradation of polyaromatic hydrocarbons (PAH) in soil model system

Total eight endophytic bacteria were isolated from the roots of Populus deltoides growing in non-contaminated sites at natural vegetation of Garhwal Himalayas, Uttarakhand, India. Among these eight, only SBER3 isolate was able to metabolize wide range of polyaromatic hydrocarbons (PAH) and other hydrocarbon used in the study i.e. anthracene, naphthalene, benzene, toluene and xylene on minimal salt basal medium (MSB) as sole source of carbon and energy. It was identified as Bacillus sp. on the basis of 16S rDNA sequence. Furthermore, quantitatively Bacillus sp. SBER3 was able to produced 22 μg ml−1 of IAA after 4 days and solubilized 0.96 μg ml−1 of available phosphorus respectively after 120 h. In addition, Bacillus sp. SBER3 also produced siderophore and 1 aminocyclopropane-1-carboxylate (ACC) deaminase. Along with these traits, SBER3 under in vitro condition inhibited the phytopathogenic fungi Rhizoctonia solani, Macrophomina phaseolina, Fusarium oxysporum and Fusarium solani with (percent growth inhibition) PGI of 60%, 61.5%, 64.3% and 12%, respectively. Microscopic examination under the influence of Bacillus sp. SBER3 revealed abnormalities of mycelia structure in case of R. solani, F. oxysporum and M. phaseolina. Although, mean growth rate and survival under varying osmotic stress regime were also evaluated under in vitro condition. Interestingly, in liquid culture medium Bacillus sp. SBER3 reduced appreciable amount i.e. 83.4% and 75.1% of anthracene and naphthalene, respectively after 6 days of incubation. Notwithstandingly, isolate SBER3 proved to be a competent rhizobacteria in rhizosphere niche in treatments T1 (Sterile soil + plant cuttings + bacterization) and T2 (sterile soil + anthracene + plant cuttings + bacterization). Rhizoremediation potential of Bacillus sp. SBER3 was demonstrated in polyaromatic hydrocarbon contaminated soil model system. Significant enhancement in shoot, root length, root and shoot biomass including stem girth of P. deltoides with respective to control was also recorded and concurrently endophytic isolate Bacillus sp. SBER3 degraded 45.6% of PAH in soil model system after 120 days as determined by HPLC analysis.