A process related to membrane potential involved in bacterial chemotaxis to galactose

Abstract

Attractants, in the presence of respiration and ATPase inhibitors, stimulate a hyperpolarization in Escherichia coli [Eisenbach, M. (1982) Biochemistry 21, 6818-6825]. In order to examine whether this hyperpolarization is correlated with chemotaxis, the effect of the attractant D-galactose and its analogues on the membrane potential of wild-type E. coli strains and some of their mutants was studied. The main observations were the following: (i) Wild-type cells became hyperpolarized by either galactose or its nonmetabolizable analogues, D-fucose and L-sorbose. (ii) A mutant defective in galactose metabolism became hyperpolarized by galactose. (iii) Inhibiting the galactose permease system did not prevent the hyperpolarization, rather it facilitated the observation of the hyperpolarization. (iv) Mutants unable to transport galactose via the methyl beta-galactoside (Mgl) transport system but having normal chemotaxis to galactose became normally hyperpolarized by D-fucose. (v) Mutants which cannot bind galactose were not hyperpolarized by galactose. (vi) The hyperpolarization in flaI mutants, in which the whole chemotaxis machinery is repressed, was reduced to 12-15% of the hyperpolarization in the parent strains. (vii) Nonattractant sugars did not stimulate hyperpolarization. It is concluded that the hyperpolarization is the consequence of neither galactose metabolism nor transport but rather is correlated with galactose taxis.

Distinction between changes in membrane potential and surface charge upon chemotactic stimulation of Escherichia coli

“…1). These results point to the conclusion that chemotaxis towards galactose (Eisenbach et al, 1983), and possibly other attractants (Eisenbach, 1982), is accompanied by ion currents, revealed under the conditions of these studies as changes in membrane potential. The identity of these ion currents as well as their signiflcance in chemotaxis are under investigation.…”

“…Fig. 5 in Eisenbach et al, 1983, for the dependence of the magnitude and duration of the TPP+ response on the D-galactose concentration). The magnitude of the TPP+ response under these conditions, -16 ± 6 mV (±SD), was very similar to the response with 10 mM KPi (Table I).…”

“…Essentially glucose-free D-galactose was from Sigma Chemical Co. (St. Louis, MO). D-fucose was purified before use by liquid chromatography as described previously (Eisenbach et al, 1983). All other chemicals were of the highest purity commercially available.…”

“…It has recently been shown that chemoattractants, including galactose, stimulate an apparent increase in membrane potential of E. coli, as monitored by a TPP+ '-electrode and detectable in the presence of a respiratory inhibitor (Eisenbach, 1982). For the case of galactose, it has been shown that this apparent hyperpolarization is correlated with chemotaxis (Eisenbach, 1983;Eisenbach et al, 1983).…”

Voltage clamp effects on bacterial chemotaxis

“…The statistical significance of the change in adaptation time in high-K+ buffer (Table 3) or with B. subtilis was, however, doubtful (P s 90%). Since the average change in adaptation time was only 24%, it seems to us that this change may be the consequence of a secondary or an indirect effect of A%s on one of the processes involved in adaptation, e.g., the chemotaxis-related hyperpolarization (12,13,15,17) (cf. Fig.…”