Genome-level insights into coordinated ethanol production and chaperone-driven stress tolerance in Bacillus cereus strain GRJBSBT-1 isolated from petroleum refinery sludge

Petroleum hydrocarbon contamination creates specialized ecological niches that present a source for mining microorganisms with exceptional metabolic flexibility and stress resilience. In this study, we performed a comprehensive genome-level analysis of Bacillus cereus strain GRJBSBT-1, isolated from petroleum refinery sludge, to elucidate the molecular coordination between ethanol production and stress tolerance, two important traits associated with microbial adaptation to ethanol-rich environments. Whole-genome sequencing revealed a 5.41-Mb circular genome with 35.3% GC content, comprising 5393 coding sequences and complete glycolytic and fermentative pathways. Functional annotation and KEGG pathway mapping identified genes associated with ethanol metabolism and protein quality-control systems involved in stress adaptation. Although several ethanol-related enzymes were detected, a complete canonical AdhE/PFOR ethanol fermentation pathway was not reconstructed. Quantitative gene expression analysis (qRT-PCR) under fermentative and ethanol-stress conditions showed significant upregulation of key fermentative genes (adhE, pdhA) and protein quality-control genes (groEL, groES), whereas the small heat-shock protein hsp20 was selectively downregulated. This transcriptional expression profile suggests differential involvement of chaperone systems during ethanol stress adaptation. Moderate ethanol exposure (5%) was associated with increased expression of groEL and selected metabolic genes, indicating a potential relationship between protein quality-control processes and ethanol-associated adaptation. The contrasting regulation of hsp20 and groES suggests differential transcriptional responses to ethanol exposure. However, these observations are based on targeted gene expression analyses and should be considered preliminary until validated through broader functional and systems-level investigations. Comparative analysis with supported possibilities of ethanologens underscores the metabolic versatility and robust stress-management capacity of strain GRJBSBT-1. These findings provide genomic and transcriptional insights into ethanol-associated metabolism and stress adaptation in B. cereus GRJBSBT-1 and may serve as a foundation for future investigations aimed at evaluating its biotechnological potential.