The Cell Wall of Bacillus Subtilis is Protonated During Growth

Abstract

The cell wall of Bacillus subtilis Marburg is a thick mat of peptidoglycan, teichoic acid and adventitiously bound proteins. The wall is 25–30 nm thick (Beveridge and Murray, 1979) and is composed of approximately equal amounts, by weight, of peptidoglycan and α-D-glucosylated teichoic acids. The strategy for the assembly of the wall is now beginning to be understood. The currently prevailing view is that wall precursors are exported through the cytoplasmic membrane, only to be covalently attached to pre-existing wall nearest the membrane. Upon insertion into the inner wall face, the young peptidoglycan strands are crosslinked into the wall mat. Once crosslinking has occurred, the newly-added wall components assume pressure and stretch. Further stretching occurs when even more new peptidoglycan strands have been inserted and crosslinked. The concept that the wall is a stress-bearing and stretchable covering of the bacterium was first proposed by Koch et al. (1982) in what is now referred to as the surface stress theory. The surface stress theory can be applied to the elongation of the cylindrical portion of the wall of B. subtilis (Mobley et al. 1984; Koch and Doyle, 1985; Kemper et al., 1988).