Department of Microbiology & Biotechnology, University School of Sciences, Gujarat University, Ahmedabad 380009, India.
Microbiol Res. 2020 Sep;238:126526. doi: 10.1016/j.micres.2020.126526. Epub 2020 Jun 18.
The current study depicts the isolation of luminescent bacteria from fish and squid samples that were collected from Veraval fish harbour. From Indian mackerel, total 14 and from squid, total 23 bioluminescent bacteria were isolated using luminescence agar medium. Two bioluminescent bacteria with highest relative luminescence intensity PBR1 and PBL1 were selected. These two isolates were subjected to detailed biochemical characterization and were tested positive for 5 out of 13 biochemical tests. Furthermore, both PBR1 and PBL1 were able to ferment cellobiose, dextrose, fructose, galactose, maltose, mannose, sucrose and trehalose with acid production. Based on 16S rRNA partial gene sequence analysis, PBR1 was identified as Vibrio alginolyticus and PBL1 as V. rotiferianus. Antibiotic susceptibility test using paper-disc method showed that PBR1 and PBL1 were sensitive to chloramphenicol, ciprofloxacin, co-trimoxazole, gatifloxacin, levofloxacin, linezolid ad roxithromycin out of 18 antibiotics tested. Moreover, both strains were evaluated for their exopolysachharide (EPS) producing ability where PBR1 and PBL1 were able to yield 1.34 g% (w/v) and 2.45 g% (w/v) EPS respectively from 5 g% (v/v) sucrose concentration. Heavy metal toxicity assessment was carried out using agar well diffusion method with eight heavy metals and both the strains were sensitive to As(III), Cd(II), Ce(II), Cr(III), Cu(II), Hg(II) and while they showed resistance to Pb(II) and Sr(II). Based on these results, a study was conducted to demonstrate bio-removal of Pb and Sr by EPS of PBR1 and PBL1. Fourier transform infrared (FTIR) spectra revealed the functional groups of EPS involved in interaction with the heavy metals. Owing to the sensitivity for the remaining heavy metals, these bioluminescent bacteria can be used further for the development of luminescence-based biosensor.
本研究从位于 Veraval 鱼港采集的鱼类和鱿鱼样本中分离出发光细菌。从印度鲭鱼中共分离出 14 株，从鱿鱼中共分离出 23 株发光细菌，使用发光琼脂培养基进行分离。选择相对发光强度最高的 2 株发光细菌 PBR1 和 PBL1 进行详细的生化特性分析，这 2 株分离株在 13 种生化试验中的 5 种试验中呈阳性。此外，PBR1 和 PBL1 均能发酵纤维二糖、葡萄糖、果糖、半乳糖、麦芽糖、甘露糖、蔗糖和海藻糖，并产酸。基于 16S rRNA 部分基因序列分析，PBR1 被鉴定为 alginolyticus 弧菌，PBL1 被鉴定为 V. rotiferianus 弧菌。纸片法药敏试验显示，PBR1 和 PBL1 对 18 种抗生素中的 16 种敏感，包括氯霉素、环丙沙星、复方新诺明、加替沙星、左氧氟沙星、利奈唑胺和罗红霉素。此外，还评估了这两种菌株产生胞外多糖 (EPS) 的能力，其中 PBR1 和 PBL1 分别能够从 5%（v/v）蔗糖浓度中产生 1.34 g%（w/v）和 2.45 g%（w/v）的 EPS。采用琼脂孔扩散法，用 8 种重金属进行重金属毒性评估，结果表明，两种菌株对 As(III)、Cd(II)、Ce(II)、Cr(III)、Cu(II)、Hg(II)敏感，而对 Pb(II)和 Sr(II)有抗性。基于这些结果，进行了一项研究，以证明 PBR1 和 PBL1 的 EPS 对 Pb 和 Sr 的生物去除作用。傅里叶变换红外 (FTIR) 光谱揭示了 EPS 与重金属相互作用的功能基团。由于对其余重金属的敏感性，这些发光细菌可进一步用于开发基于发光的生物传感器。
