Studies on Negative Chemotaxis and the Survival Value of Motility in Pseudomonas Fluorescens

Abstract

SUMMARY Multiplication of aerobic piliated fla+ and fla- Pseudomonas jluorescens growing in aerated mixed culture gave fla+: fla- ratios approximately I : I over a 24 hr growth period. When fla+ and fla- were cultured simultaneously in non-aerated media, fla+ then outgrew the fla- mutant to a final (24 hr) ratio of I o : I or greater, thereby lending supporting evidence to the view that motility is a survival factor in environments where 'nutrients' are limited or discontinuous. Gravity, magnetism, and light did not influence a negative chemotactic response of fla+ P.Jlu0rescen.s to hydrogen ions. Temperature variations, pH, or viscosity alterations either inhibited or stimulated motility, thereby making impossible a determination of their specific effects. Various antibiotics, membrane-active agents, and protein or DNA synthesis inhibitors were employed in attempts to interfere with the chemotactic response, but none completely inhibited chemotaxis without also affecting motility. The cyto- plasmic membrane may act as a transducer of environmental stimuli in chemotaxis.