Redox sensing by Escherichia coli:: effects of dithiothreitol, a redox reagent reducing disulphides, on bacterial growth

Escherichia coli is able to grow with a high rate under anaerobic conditions upon decrease in redox potential (E,,) both either in slightly alkaline (pH 7.5) or acidic (pH 5.5) medium. Upon transition of E coli MC4100 culture to stationary growth phase a decrease in E-h from the positive values of +120 to +160 mV to the negative ones of -380 to -550 mV, and the H-2 production are observed at various pH. A redox reagent DL-dithiothreitol (DTT) in a concentration of 3 mM reduces Eh to the negative values, and increases a latent (lag) growth phase duration, as well as delays a logarithmic growth phase independently of pH. At alkaline and acidic pH the changes in membrane potential (DeltaPsi) are observed in the presence of 3 mM DTT. K+ uptake is recovered. At pH 5.5 the H-2 production is suppressed by DTT only in a higher concentration of 10 mM. The results suggest DTT effects that are in addition to the effects of E-h. The mechanism of DTT action on bacterial growth might be intermediated through thiol group modulation of the membrane proteins, which is reflected as the generation of DeltaPsi as well as K+ accumulation and the activity of the membrane-associated enzymes. (C) 2004 Elsevier Inc. All rights reserved.