L-CARNITINE METABOLIZATION AND OSMOTIC-STRESS RESPONSE IN ESCHERICHIA-COLI

Growth of Escherichia coli 044 K 74 in liquid medium of raised osmotic strength was stimulated by exogenous L‐carnitine, crotonobetaine and γ‐butyrobetaine, respectively. L‐Carnitine was accumulated within the cells in dependence on the salt concentration of the media. Osmotic stress during aerobic or anaerobic growth with glucose triggered the L‐carnitine uptake in E. coli 044 K 74 whereas L‐carnitine uptake by cells of this organism grown anaerobically on glycerol/fumarate was only slightly modified. Synthesis of the enzymes metabolizing L‐carnitine to γ‐butyrobetaine in glycerol/fumarate growing bacteria was found to be completely repressed by high NaCl‐concentrations. Together, these results indicate that most likely the L‐carnitine metabolization sequence does not play a role in osmoregulation in E. coli 044 K 74. Copyright © 1990 Wiley‐VCH