Characterization of Pseudomonas aeruginosa fatty acid profiles in biofilms and batch planktonic cultures.

The fatty acid composition of Pseudomonas aeruginosa PAO1 was compared between biofilm and batch planktonic cultures. Strain PAO1 biofilms were able to maintain a consistent fatty acid profile for up to 6 days, whereas strain PAO1 batch planktonic cultures showed a gradual loss of cis-monounsaturated fatty acids over 4 days. Biofilms exhibited a greater proportion of hydroxy fatty acids but a lower proportion of both cyclopropane fatty acids and saturated fatty acids (SAFAs). SAFAs with >=16 carbons, in particular, decreased in biofilms when compared with that in batch planktonic cultures. A reduced proportion of SAFAs and a decline in overall fatty acid chain length indicate more fluidic biophysical properties for cell membranes of P. aeruginosa in biofilms. Separating the biofilms into 2 partitions and comparing their fatty acid compositions revealed additional trends that were not observed in the whole biofilm: the shear-nonremovable layer consistently showed greater proportions of hydroxy fatty acid than the bulk liquid + shear-removable portion of the biofilm. The shear-nonremovable portion demonstrated a relatively immediate decline in the proportion of monounsaturated fatty acids between days 2 and 4; which was offset by an increase in the proportion of cyclopropane fatty acids, specifically 19:0cyc(11,12). Simultaneously, the shear-removable portion of the biofilm showed an increase in the proportion of trans-monounsaturated fatty acids and cyclopropane fatty acids.