Stimulation of the anaerobic growth of Salmonella typhimurium by reduction of L-carnitine, carnitine derivatives and structure-related trimethylammonium compounds.

In view of the development of a L-carnitine deficiency, the metabolism of L-carnitine and structure-related trimethylammonium compounds was studied in Salmonella typhimurium LT2 by means of thin-layer chromatography (TLC). L-Carnitine, crotonobetaine and acetyl-L-carnitine stimulated the anaerobic growth in a complex medium significantly. The stimulation depended on the formation of gamma-butyrobetaine. The reduction of L-carnitine proceeded in two steps: (1) Dehydration of the L-carnitine to crotonobetaine, (2) hydrogenation of crotonobetaine to gamma-butyrobetaine. The reduction of crotonobetaine was responsible for the growth stimulation. Terminal electron acceptors of the anaerobic respiration such as nitrate and trimethylamine N-oxide, but not fumarate, suppressed the catabolism of L-carnitine completely. Glucose fermentation, too, inhibited the reduction of L-carnitine but optimal growth with a high carnitine catabolism was achieved by D-ribose. The esters of carnitine with medium- and long-chain fatty acids inhibited the growth considerably because of their detergent properties.