Growth temperature-dependent expression of structural variants of Listeria monocytogenes lipoteichoic acid

Investigating the expression of lipoteichoic acid (LTA) from Listeria monocytogenes, we found two distinct structural variants of LTA (LTA1 and LTA2) using NMR and MS technology. While both LTA consisted of a poly-glycerophosphate backbone bound via a disaccharide to a diacyl-glycerol moiety, one LTA type (LTA2) possessed a second phosphatidyl diacyl-glycerol moiety. As examined by human whole blood incubations, the cytokine inducing potential of LTA1 was comparable to that of other LTA, like LTA from S. aureus. In contrast, LTA2 induced significantly less of the pro-inflammatory cytokines but not of the anti-inflammatory IL-10, and failed to activate the L-ficolin dependent pathway of complement in vitro. Most interestingly, changes in growth temperature induced a switch in the expression levels of LTA1 and LTA2 in the cell wall: while the amount of LTA1 was comparable, the expression of LTA2 was low when Listeria were grown at room temperature in broth (ratio of LTA1 to LTA2 was 1:0.06), but increased when Listeria were grown at 37°C (ratio of LTA1 to LTA2 was 1:0.68). The observed shift in LTA expression, probably accompanying the switch from the saprophytic to the virulent state, indicates an important adaptation to the different structural requirements inside the host cells.JRC.I.2-Validation of Alternative Method