Characterization and genome-based analysis of a crude oil-degrading Bacillus sp. THW isolated from estuarine sediment

Crude oil contamination poses a persistent threat to estuarine ecosystems, and microbial bioremediation offers an environmentally friendly and cost-effective strategy for mitigating petroleum pollution. It is therefore of great significance to isolate highly efficient crude oil-degrading strains from marine sediments and to investigate their degradation potential and underlying genomic mechanisms. In this study, a crude oil-degrading bacterium, designated strain THW, was isolated from sediment collected in the Liao River estuary, China. Based on 16S rRNA gene sequencing and phylogenetic analysis, the isolate was identified as Bacillus sp. Strain THW exhibited an apparent crude oil removal efficiency of 56.1% at an initial concentration of 5 g/L within 8 days at 30 °C, pH 7.0, and 5‰ salinity, and it maintained growth and apparent crude oil removal across a range of crude oil concentrations, pH, and salinity levels. Genome sequencing revealed a 3,924,707-bp genome with a GC content of 46.59% and 4,088 predicted protein-coding genes. Functional annotation identified several genes encoding enzymes with potential relevance to downstream hydrocarbon- or xenobiotic-related metabolism, including alcohol and aldehyde dehydrogenases, but the genetic basis for the initial oxidation of n-hexadecane remains unresolved. These findings suggest that Bacillus sp. THW possesses considerable crude oil-degrading potential and provide genome-based evidence for its possible hydrocarbon-degradation capacity, supporting its potential application in petroleum-contaminated estuarine environments.