THE PSS AND PSD GENES ARE REQUIRED FOR MOTILITY AND CHEMOTAXIS IN ESCHERICHIA-COLI

Mutants of Escherichia coli defective in phosphatidylserine synthase ( encoded by pss) and phosphatidylserine decarboxylase (encoded by psd) make cell membranes deficient in phosphatidylethanolamine. In this rep ort we show that wild-type pss and psd genes are required for motility and chemotaxis. Null mutants or strains with temperature-sensitive ps s or pad mutations grown at high temperature (35 degrees C) were nonmo tile. They lacked flagella and showed reduced rates of transcription o f the flhD master operon (encoding FlhD and FlhC), the fliA operon (en coding sigma(F)), and the fliC operon (encoding flagellin). At low tem perature (25 degrees C), the temperature-sensitive mutant cells showed motility and chemotaxis but at reduced levels. The extent of the moti lity and chemotaxis defects in the mutants was correlated with the amo unt of phosphatidylethanolamine in the membranes, suggesting a link be tween membrane phospholipid composition and expression of the flagellu m chemotaxis regulon.