Fatty acid adaptation in an Antarctic bacterium - Changes in primer utilization

The fatty acid composition and temperature/growth characteristics of a psychrophilic bacterium, strain ACAM 456, isolated from Antarctic sea-ice is reported. The bacterium produced acyl components that may be grouped in three different carbon chain types: even-chain, odd-chain and iso-branched odd-chain. The proportions of these chain types varied according to growth temperature, and were manipulated by growth on L-serine, L-leucine or propionic acid as sole carbon sources. De novo fatty acid synthesis was investigated using sodium [1-C-14]acetate, L-[U-C-14]leucine and L-[U-C-14]serine as radioactive precursors. Compared with a control culture, resuspension of mid-exponential phase cells in artificial seawater led to a change in the selection and/or intracellular availability of acyl chain primer molecules, The proportion of radiolabel incorporated into even-chain length components from cells declined, whereas the percentage of radiolabel present in odd-chain length components increased, An increase in incubation temperature augmented this effect, and also elicited a rise in the proportion of label present in branched-chain products. ACAM 456 manipulated the utilization of acyl chain primer molecules as an adaptive response to changes in environmental conditions, In particular, the regulation of odd-chain length fatty acids is described as a novel adaptational response.