Potassium Uptake During Microcyst Formation in Myxococcus xanthus

Abstract

The kinetics of 42 K uptake by Myxococcus xanthus during vegetative growth and microcyst formation were determined. In the medium studied, growing cells concentrated potassium about 100-fold, yielding an intracellular concentration of 147 m m . The influx of K + in growing cells was 17 ± 3 pmoles of K + /cm 2 min. About 5 hr after induction of vegetative cells to microcysts, the K + influx decreased and the intracellular concentration fell. By 18 hr after induction, there was no measurable influx of K + , and the intracellular concentration of potassium was less than 29 m m . There was, however, considerable binding of K + to the “surface” of microcysts. It is postulated that the greatly reduced intracellular concentration of potassium helps to maintain the microcyst in its dormant state and protects it against enzymatic break-down.