Integrated Analysis of Paired Crude Oil and Produced Water Reveals Stress-Tolerant Hydrocarbon-Degrading Bacteria with Bioremediation Potential.

Oilfield microbiome studies have extensively characterized microbial community composition or isolated individual hydrocarbon degraders, but integrated exploration of cultivable functional bacteria from paired crude-oil and produced-water environments remains limited, particularly for strains combining hydrocarbon utilization with stress-tolerance and biosurfactant-related traits. In this study, paired crude-oil and produced-water samples from the Huoshaoshan Oilfield were investigated by combining 16S rRNA amplicon sequencing with culture-dependent isolation and functional screening. A total of 135 bacterial isolates representing 22 genera were recovered, of which 70 showed hydrocarbon-utilizing potential in primary screening. The collection also included isolates capable of growth at 10% NaCl and up to 55 °C. Comparison of sequencing and cultivation revealed marked differences between environmental abundance and recoverable functional resources. Representative isolates showed distinct removal profiles toward n-tetracosane (C24), naphthalene, phenanthrene, and fluoranthene under saline conditions, with Halomonas nitritophilus Ff1 and Halomonas sp. Fc15 showing particularly strong performance. Sequence-confirmed alkB and PAH-RHDα fragments provided additional molecular support for the observed hydrocarbon-removal phenotypes. A three-strain consortium composed of Sphingomonas sp. Fa24, Halomonas nitritophilus Ff1, and Stutzerimonas stutzeri Ff2 achieved 87.4% C24 removal, exceeding the corresponding monocultures. These findings link oilfield microbial community profiling with cultivable functional resource mining and provide candidate strains for saline petroleum bioremediation.