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

International audienceThis 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 (neicosane, sodium acetate and rich medium), temperature (13, 20 and 30³C), 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 s temperature s growth phasevoxygen. Among the different growth substrates, n-eicosane (nC PH) led to the most distinct FA profiles, characterised by high amounts of saturated and branched FA, the appearance of 20-carbon acids (20:1g9 and 20:0) and a v IH 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 4C IVXI /4C ITXI 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