Regulation of Bacillus subtilis macrofiber twist development by ions: effects of magnesium and ammonium

The steady-state twist of Bacillus subtilis macrofibers produced by growth in complex medium was found to vary as a function of the magnesium and ammonium concentrations. Four categories of macrofiber-producing strains that differed in their response to temperature regulation of twist were studied. Macrofibers were cultured in the complex medium TB used in previous experiments and in two derivative media, T (consisting of Bacto Tryptose), in which most strains produced left-handed structures, and Be (consisting of Bacto Beef Extract), in which right-handed macrofibers arose. In nearly all cases, increasing concentrations of magnesium led to the production of macrofibers with greater right-handed twist. Some strains unable to form right-handed structures as a function of temperature could be made to do so by the addition of magnesium. Inversion from right- to left-handedness in strain FJ7 induced by temperature shift-up was blocked by the addition of magnesium. The presence of magnesium during a high-temperature pulse did not block the establishment of "memory," although it delayed the initiation of the transient inversion following return to low temperature. The twist state of macrofibers grown without a magnesium supplement was not instantaneously affected by the addition of magnesium. Such fibers were, however, protected from lysozyme attack and associated relaxation motions. Lysozyme degradation of purified cell walls (both intact and lacking teichoic acid) was also blocked by the addition of magnesium. Ammonium ions influenced macrofiber twist development towards the left-hand end of the twist spectrum. Macrofiber twist produced in mixtures of magnesium and ammonium was strain and medium dependent.(ABSTRACT TRUNCATED AT 250 WORDS)