Proteomic insights into the marine obligate hydrocarbonoclastic bacteria (OHCB) during alkane degradation

Obligate hydrocarbanoclastic bacteria (OHCB) typically dominate microbial communities after marine oil spills due to their distinct ability to utilize hydrocarbons as sole carbon and energy sources. They perform key roles in the natural attenuation of oil pollution, but also have the potential to be used in bioremediation strategies. To understand the enzymes involved in alkane degradation in three key OHCB (Thalassolituus oleivorans MIL-1, Alcanivorax borkumensis SK2, and Oleispira antarctica RB-8), LC-MS/MS shotgun proteomics was performed on cells growing on different hydrocarbons. T. oleivorans grew equally well on all substrates tested (n-C10-n-C32) as it utilised a subterminal alkane oxidation pathway whilst growing on long chain-alkanes, evidenced by significant upregulation of Baeyer-Villiger monooxygenase and an esterase, proteins catalysing ketone and ester metabolism, respectively. Whilst growing on the branched alkane pristane A. borkumensis not only biosynthesised a cytochrome P450, an alcohol oxidase and an alcohol dehydrogenase but also expressed a set of enzymes for β-oxidation of the resultant fatty acids generated during hydrocarbon degradation, overcoming potential steric hindrance. The mechanisms O. antarctica utilises to provide it with ecological competitiveness in cold environments were identified by an increase in spectral counts for proteins involved in flagella structure/output to overcome higher viscosity, flagella rotation to accumulate cells, and proline metabolism to counteract oxidative stress, during growth at 4°C compared to 16°C. Overall, this thesis gives insight into understanding the physiology and ecology of hydrocarbonoclastic bacteria, the process of natural remediation of oil, underpins future ‘omics’ studies, and identifies enzymes with potential industrial applications and may aid rational decisions in the design of future bioremediation strategies for oil pollution.