Membrane-protein-based insights into anthracene degradation by Bacillus firmus and its enhancement by rhamnolipids

This study aimed to investigate the membrane protein dynamics of Bacillus firmus during anthracene (ANT) biodegradation and elucidate the enhancement mechanism of rhamnolipids (RLs) in ANT bioremediation.

Bacillus firmus was adapted for ANT degradation. Proteomics analyzed membrane protein dynamics during ANT biodegradation (100 mg∙L-1), supplemented with microscopic/spectroscopic analyses of cellular changes. Phenotypic validation included measurements of degradation efficiency, cell surface hydrophobicity (CSH), and membrane permeability. Adaptation enabled B. firmus to degrade 80.42% of ANT within 96 h. Proteomics revealed a coordinated strategy: upregulation of extracellular polysaccharide/protein secretion (substrate uptake), flagellar proteins (improved chemotaxis), and detoxification enzymes (reduced cellular stress). Supplementation with 100 mg∙L-1 RLs increased ANT degradation to 81.35% (1.22-fold enhancement), correlating with a 7.52-fold increase in CSH and improved membrane permeability. Microscopic/spectroscopic analyses showed RL-induced structural modifications: capsule thickening, fatty acid depletion, and functional group alterations enhancing ANT bioavailability and cellular uptake.

Bacillus firmus employs a dual adaptation strategy for ANT remediation: optimizing catabolic processes while mitigating cytotoxicity. RLs significantly enhance bioremediation by modulating bacterial membrane structure and function, thereby improving ANT bioavailability and cellular uptake. Combining proteomics with phenotypic validation establishes a framework for biosurfactant-enhanced bioremediation, offering scalable solutions for PAH management.