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The Wax–Liquid Transition Modulates Hydrocarbon Respiration Rates in Alcanivorax borkumensis SK2

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journal contribution
posted on 17.04.2018 by Li-Na Lyu, Haibing Ding, Zhisong Cui, David L. Valentine
Marine hydrocarbon biodegradation is an important environmental process conducted by microbes and modulated by oceanographic conditions. Following up on the patterns of petroleum hydrocarbon biodegradation observed after the Deepwater Horizon disaster, we measured respiration rates for the obligate alkane-degrading bacterium, Alcanivorax borkumensis SK2, to assess the relationship between hydrocarbon respiration rates and the phase, wax versus liquid, of the substrate. Using a matrix of temperatures (20, 25, 30, 35, and 40 °C) and n-alkanes (n-C14, n-C15, n-C16, n-C17, n-C18, n-C19, and n-C20) for which each temperature gap spans the phase transition point of an n-alkane, we demonstrate that the n-alkane respiration rate decreases substantially when the substrate is in the wax versus liquid phase. The observed effect spans the full experimental temperature range. Subsequent experimentation with only wax-phase n-C19 indicates that the availability of surface area modulates the n-alkane respiration rate and is likely a factor contributing to the observed respiration rates being lower for wax-phase than for liquid-phase hydrocarbons. These results demonstrate that wax-phase hydrocarbons are subject to biodegradation by A. borkumensis SK2 but that rates are suppressed relative to those of liquid-phase hydrocarbons. The results are consistent with interpretations of hydrocarbon biodegradation patterns from Deepwater Horizon with broader relevance to the behavior of hydrocarbons in the ocean.