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(h)) 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 3mM reduces E(h) 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 3mM 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.

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