Rhodococcus erythropolis ICBD2 membrane and cell wall adaptation to long-chain alkane degradation

Abstract Long-chain hydrocarbon biodegradation is limited by its low bioavailability. Specific strains degrade hydrocarbons including long-chain alkanes. Rhodococcus erythropolis ICBD2 is a hydrocarbonoclastic bacterium isolated from a chronically petroleum-contaminated coastal soil from Valparaiso Region, Central Chile. The aims of the study were the characterization of catabolic genes and the adaptation of the membrane, cell wall, morphology, and metabolism of R. erythropolis ICBD2 to long-chain alkane n-eicosane. Genes encoding alkane monooxygenases involved in the degradation of different chain length alkanes (five alkB, almA, and ladA), cytochrome monooxygenases (seven cyp), and Baeyer–Villiger-type monooxygenases (ethA, pamO and PA1538) are distributed in ICBD2 genome. R. erythropolis ICBD2 showed significant growth (turbidity600nm ~ 1.0) on n-eicosane (5 mM) as sole carbon and energy source. ICBD2 cells grown on n-eicosane reduced the cellular surface area and increased hydrophobicity compared to acetate-grown bacteria. In comparison with acetate-grown cells, bacteria grown on n-eicosane increased the saturation and reduced the chain length of their membrane fatty acids (FA) and cell wall mycolic acids (MA), resulting in a more rigid and stable cellular structure. During growth on n-eicosane, strain ICBD2 increased the expression of alkB1, alkB2, and almA catabolic genes and reduced the expression of kasAB gene associated with the elongation of fatty acids. Remarkably, in this study we presented for the first time the adaptive response of Rhodococcus to growth on a long-chain alkane both at structural and metabolic levels. The results are useful to uncover Rhodococcus mechanisms of adaptation to long-chain alkanes, which are crucial for bioremediation of low bioavailable petroleum hydrocarbons. Key points • n-Eicosane increases hydrophobicity and hydrocarbon adhesion of Rhodococcus cells • n-Eicosane increases saturation and decreases lengths of membrane FA and cell wall MA • In strain ICBD2, n-eicosane induced the expression of alkB1, alkB2, and almA genes