Abstract

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.

摘要

萘是一种简单的多环芳烃（PAH），被认为是一种常见的环境污染物。从印度瓜廖尔 (MP) 的不同石油污染地点获得的总共 16 种细菌分离物进行了萘降解潜力的筛选。通过用溶解在丙酮中的 100 mg l ^-1萘修正培养基，使用富集方法分离细菌。在 16 种细菌分离物中，只有两种被命名为 RS2(3) 和 GS2 的分离物显示出良好的萘降解潜力，基于 1000 mg l ^{-1的最大耐受水平}分离株在 600 nm 处的光密度 (OD) 分别为 0.536 和 0.133。降解通过 GC 分析确定，GS2 显示 73% 和 48% 降解，而 RS2(3) 显示 52% 和在 100 和 200 mg l ^-1萘浓度下分别为 29%。分离物的特征还在于它们对不同浓度（0.1%、0.5% 和 1.0%）的四种选定重金属（镉、铬、铜和锌）的重金属耐受性。在总共 16 种细菌分离物中，只有 12 种被发现对 1% 浓度的四种重金属中的任何一种具有抗性。此外，还确定了分离物对四种不同抗生素的抗生素敏感性。这些分离株在形态学、生化学上进行了表征，并被鉴定为菌株Bacillus licheniformis JUG GS2 (MK106145) 和Bacillus sonorensis JUG (RS2(3)) (MK156710) 通过 16S rRNA 基因测序。该研究推断地衣芽孢杆菌和索诺芽孢杆菌菌株也有助于修复由萘和重金属引起的污染。