Changes in fatty acids of Pseudomonas nautica, a marine denitrifying bacterium, in response to n-eicosane as carbon source and various culture conditions

Abstract

This study determined the effects of shifts in environmental conditions on the fatty acid composition of a sedimentary facultative anaerobic denitrifying marine bacteria (Pseudomonas nautica strain IP 617). The effects of carbon source (n-eicosane, sodium acetate and rich medium), temperature (13, 20 and 30°C), presence or lack of oxygen and growth phase (stationary and exponential) were investigated. As demonstrated by correspondence analysis, the effect of the various conditions tested, in descending order of importance, were carbon source>temperature>growth phase≥oxygen. Among the different growth substrates, n-eicosane (nC20) led to the most distinct FA profiles, characterised by high amounts of saturated and branched FA, the appearance of 20-carbon acids (20:1ω9 and 20:0) and a Δ10 methyl branched series with mainly the 10Me16:0. With regard to temperature effects, P. nautica showed a mean acyl chain length thermoregulation process for the major monounsaturated fatty acids which led to increased values of the ratio ΣC18:1/ΣC16:1 with increasing temperatures. The effect of growth phase and anaerobiosis were less marked. The analysis of bacterial fatty acids could enable the detection of hydrocarbonoclastic bacterial communities in marine sediments contaminated by hydrocarbons.