ABSTRACT

The present study was undertaken to characterize the Cr(VI)-resistant bacteria isolated from the chromite mine area of Sukinda, Odisha through 16S rRNA sequencing technique followed by homology search, secondary structure analysis. The 16S rRNA sequencing resulted in varied bacterial sequence lengths. Characterization of these isolated sequences showed the dominance of the members of the genera Bacillus, Lysinibacillus, and Staphylococcus followed by the members of other distinct genera such as Enterobacter, Curtobacterium, Kocuria, and Stenotrophomonas. Cr(VI)-tolerant study of these bacterial isolates exhibited comparatively higher resistance toward Cr(VI) at 500 mg L⁻¹ concentration. Secondary-structural diversity among isolated sequences obtained from mfold prediction server varied with sequence-based diversity with some conserved pattern observed among the few Bacillus groups and Staphylococcus groups, but in other genera, the structural similarity is not observed. Multiple sequence alignment of all 16S rRNA sequences showed monomorphic and polymorphic sites in most of the sequences, whereas parsimony-informative sites were identified in a few bacterial isolates. Further, phylogenetic analysis of the isolated chromium-resistant 16S rRNA bacterial sequences along with the sequences retrieved from NCBI’s ENTREZ database was performed to study their divergence. Phylogenetic analysis revealed that chromate-resistant sequences were clustered into two distinct clades in maximum parsimony-based phylogenetic tree construction.

摘要

通过16S rRNA测序技术，然后通过同源性搜索，二级结构分析，对从奥里萨邦苏金达的铬铁矿地区分离出的耐Cr（VI）细菌进行了表征。16S rRNA测序导致不同的细菌序列长度。这些分离的序列的表征显示了芽孢杆菌属，溶菌杆菌属和葡萄球菌属的成员占优势，其次是其他不同属的成员，如肠杆菌属，弯曲杆菌属，科库里亚属和嗜麦芽单胞菌。这些细菌分离株的Cr（VI）耐受性研究在500 mg L ^-1时表现出相对较高的对Cr（VI）的抗性浓度。从mfold预测服务器获得的分离序列之间的二级结构多样性随基于序列的多样性而变化，在少数芽孢杆菌群和葡萄球菌中观察到一些保守的模式群体，但在其他属中，未观察到结构相似性。所有16S rRNA序列的多序列比对显示大多数序列中的单态和多态位点，而在一些细菌分离物中鉴定出简约信息位点。此外，对分离的抗铬16S rRNA细菌序列以及从NCBI的ENTREZ数据库检索的序列进行了系统发育分析，以研究它们的差异。系统发育分析表明，在基于简约的系统进化树构建中，抗铬酸盐序列被聚集成两个不同的进化枝。