Acetate acts as a protonophore and differentially affects bead movement and cell migration of the gliding bacterium Cytophaga johnsonae (Flavobacterium johnsoniae)

Abstract

Cells of Cytophaga johnsonae (now Hawobacterium johnsoniae) are able to translocate on solid surfaces but are unable to swim in liquid media. Organelles that may be involved in this gliding motility have not been detected, and the mechanism(s) responsible remains unknown. The movement of latex beads attached to the cell surface is considered by some to be a manifestation of the gliding machinery. In this study, acetate (in nutrient-level quantity, 45 mM) was found to inhibit bead movement on cell surfaces, whilst formation and movement of groups of cells (rafts) and typical colony spread were not affected; generation time (in liquid culture) was only slightly increased. Since acetate is a weak acid and is recognized as a protonophore, various electron-transport-associated features were assessed in an effort to understand the differential effects of acetate on bead movement and cell motility. Selected protonophores and electron transport inhibitors were tested to compare their effects on cell translocation and metabolic activities with those of acetate. Although 0 , consumption was not significantly affected in the presence of acetate and the protonmotive force decreased only minimally, ATP levels were markedly decreased. Arsenate and cyanide were also shown to inhibit bead movement but did not inhibit either movement of rafts of cells or colony spreading. Cyanide lowered 0, consumption, while arsenate did not; both compounds effected substantial decreases in cellular ATP content, but little or no decrease in protonmotive force. The inhibitory effects of these compounds on bead movement over cell surfaces contrasted with the continued ability of cells to form rafts, to glide and to form spreading colonies and led to the conclusion that bead movement is not a complete correlate of the gliding machinery of C. johnsonae. In addition, it seems likely that bead movement is more affected by the level of cellular ATP than it is b y the protonmotive force, which has been assumed to provide the energy (derived from the transmembrane gradients) for the gliding machinery.

Frozen motion of gliding bacteria outlines inherent features of the motility apparatus

“…This was achieved effectively by using cyanide and azide as potent inhibitors of electron transport (Ridgway, 1977) : these are weak proton ionophores and cause a partial breakdown of the membrane potential (Harold, 1972(Harold, , 1977Duxburry et al, 1980 ;Dzink-Fox et al, 1997). Our data show for the first time the obvious impact of electron flow inhibition on surface features of actively gliding cells.…”

Helical flow of surface protein required for bacterial gliding motility

“…Previous studies indicated that proton motive force (PMF) powers gliding of Flavobacterium and related gliding bacteria (21)(22)(23)(24). To determine whether the SprB motion is powered by PMF, we examined the effects of carbonyl cyanide m-chlorophenylhydrazone (CCCP), a PMF uncoupler, on SprB motion.…”

Flavobacterium johnsoniaeGliding Motility Genes Identified bymarinerMutagenesis

“…The gliding motor converts chemical energy into mechanical work. Previous studies indicate that proton motive force (PMF) is required for gliding (12,34). ATP may also be needed, since it has been reported that cells depleted for ATP fail to propel latex spheres (12).…”

“…Previous studies indicate that proton motive force (PMF) is required for gliding (12,34). ATP may also be needed, since it has been reported that cells depleted for ATP fail to propel latex spheres (12). The motor presumably has one or more components that span the cytoplasmic membrane to harvest cellular energy.…”