Effect of different carbon sources on membrane permeability, membrane fluidity, and fatty acid composition of a psychrotrophic Acinetobacter sp HH1-1during growth at low temperatures and after cold shock

The effect of different carbon sources on the ability of a psychrotrophic A cinetobacter sp., strain HH1-1, to grow at low temperatures and respond to cold shock was investigated by monitoring cell membrane permeability, membr ane fluidity and fatty acid composition. Cells were grown in batch cultures with acetate, Tween 80 or olive oil as the sole source of carbon and incub ated at 25, 5 degrees C or subjected to a 25 to 5 degrees C decrease in gro wth temperature (cold shock). Cell membrane changes were observed following cold shock for all carbon sources. Cells became leaky and membranes less f luid immediately after cold shock. The fatty acid composition of cells also varied significantly with carbon source. A higher content of oleic acid (c is-Delta 9-octadecenoic acid - 18:1) was observed in cells grown in the pre sence of Tween 80 and olive oil compared to cells grown in the presence of acetate. Increased content of palmitoleic acid (cis-Delta 9-hexadecenoic ac id - 16:1) observed during growth at 5 degrees C and following cold shock i ndicated that this fatty acid may be important for growth at low temperatur es. Acetate-grown cells responded more quickly to cold shock than did Tween 80 or olive oil-grown cells by restoring membrane fluidity and by taking K + back into the cells. In addition, acetate-grown cells modified the conten t of fatty acid cis-Delta 9-hexadecenoic acid at 2 h post cold shock as opp osed to 24 h post cold shock in cells grown in the presence of Tween 80 or olive oil. This research indicated that cells are most affected by rapid de creases in growth temperature and growth at low temperatures when cells uti lized olive oil as the sole source of carbon.