AUTHOR=Gregson Benjamin H. , Metodieva Gergana , Metodiev Metodi V. , Golyshin Peter N. , McKew Boyd A. 

TITLE=Differential Protein Expression During Growth on Medium Versus Long-Chain Alkanes in the Obligate Marine Hydrocarbon-Degrading Bacterium Thalassolituus oleivorans MIL-1

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.03130

DOI=10.3389/fmicb.2018.03130

ISSN=1664-302X

ABSTRACT=<p>The marine obligate hydrocarbonoclastic bacterium <italic>Thalassolituus oleivorans</italic> MIL-1 metabolizes a broad range of aliphatic hydrocarbons almost exclusively as carbon and energy sources. We used LC-MS/MS shotgun proteomics to identify proteins involved in aerobic alkane degradation during growth on medium- (<italic>n</italic>-C<sub>14</sub>) or long-chain (<italic>n</italic>-C<sub>28</sub>) alkanes. During growth on <italic>n</italic>-C<sub>14</sub>, <italic>T. oleivorans</italic> expresses an alkane monooxygenase system involved in terminal oxidation including two alkane 1-monooxygenases, a ferredoxin, a ferredoxin reductase and an aldehyde dehydrogenase. In contrast, during growth on long-chain alkanes (<italic>n</italic>-C<sub>28</sub>), <italic>T. oleivorans</italic> may switch to a subterminal alkane oxidation pathway evidenced by significant upregulation of Baeyer-Villiger monooxygenase and an esterase, proteins catalyzing ketone and ester metabolism, respectively. The metabolite (primary alcohol) generated from terminal oxidation of an alkane was detected during growth on <italic>n-</italic>C<sub>14</sub> but not on <italic>n-</italic>C<sub>28</sub> also suggesting alternative metabolic pathways. Expression of both active and passive transport systems involved in uptake of long-chain alkanes was higher when compared to the non-hydrocarbon control, including a TonB-dependent receptor, a FadL homolog and a specialized porin. Also, an inner membrane transport protein involved in the export of an outer membrane protein was expressed. This study has demonstrated the substrate range of <italic>T. oleivorans</italic> is larger than previously reported with growth from <italic>n</italic>-C<sub>10</sub> up to <italic>n</italic>-C<sub>32</sub>. It has also greatly enhanced our understanding of the fundamental physiology of <italic>T. oleivorans</italic>, a key bacterium that plays a significant role in natural attenuation of marine oil pollution, by identifying key enzymes expressed during the catabolism of <italic>n</italic>-alkanes.</p>