Bacillus subtilis cells grown under
phosphate starvation induce
teichuronic acid (TUA) synthesis while simultaneously repressing teichoic
acid synthesis (TA). The turnover rates of TA-containing and TUA-containing walls are similar, indicating that
autolysin function is similar and suggesting that modulation of autolytic function may be similar. In this study, it is demonstrated, utilizing
fluorescein isothiocyanate (
FITC)-dextran to probe the wall pH, that a low pH exists in the wall matrix. A second probe,
cationized ferritin (CF), was used to observe cell surface protonation.
Suspensions of B. subtilis cells containing either TA or TUA were aggregated with CF only after the addition of a proton-motive-force-dissipating agent. Respiring B. subtilis TUA-containing cells labelled with
FITC-dextran exhibited little fluorescence. Conversely, fluorescence intensities exhibited by cells de-energized with
nitrogen gas were significantly greater. The effects of protonmotive force on autolytic activity were studied by adding cell wall
protein extract containing concentrated
autolysin to exponentially growing TA-containing and TUA-containing B. subtilis cells. Both TUA-containing and TA-containing cells were lysed only after the addition of
sodium azide. These data suggest that during normal growth the wall of TUA-containing B. subtilis cells is protonated, and proton-motive force influences autolytic regulation in both TUA-containing and TA-containing B. subtilis cells.