Involvement of cell fatty acid composition and lipid metabolism in adhesion mechanism of Listeria monocytogenes

The cell fatty acid (FA) composition of adhered and floating cells of two Listeria monocytogenes strains, CH4 and CH8, having respectively the highest and the lowest biofilm forming ability, among a number of selected strains, was taken into consideration. Anteiso-15:0, iso-C15:0 and anteiso-17:0 resulted the principal FAs in floating cells. On the other hand the adhered cells of the two strains presented a FAs profile characterized by a prevalence of straight FAs such as hexadecanoic acid (16:0) and octadecanoic acid (18:0). When adhered and free floating cells of the two strains were separately exposed to acid stress, an increase of the single and total branched FAs was observed both in floating and adhered cells of CH4 and in floating cells of CH8. The acid stress gave rise in the adhered cells of CH8 at relevant intracellular accumulation of straight medium chain FAs. Straight long chain and medium chain free fatty acids (FFAs) were released in the colture supernatants particularly by the strain CH4. The exposure of the latter strain to its own supernatants (conditioned media – CMs -) enhanced the C16:0 and C18:0 accumulation. An unusual extent of straight medium chain hydrocarbons like n-decane, n-undecane, n-dodecane, n-tridecane has been identified particularly in the supernatants of CH4 and CH8 strains. Moreover, long chain hydrocarbons such as pentadecane and nonadecane were released by both strains when exposed to acid stress. Because adhesion is connected with hydrophobic link of the cells with glass and ionic interactions, these hydrophobic molecules could have a key role in the adhesion and deadhesion mechanisms