Localised insertion of new cell wall in Bacillus subtilis

Abstract

THE geometry of the growth of the bacterial cell surface has been studied by following the segregation of differentially labelled old and new areas of the envelope^1–10. Results obtained with rod-shaped bacteria led to apparently contradictory interpretations⁵. The incorporation of labelled precursors into the cell wall of Gram-positive bacilli has failed to reveal segregation and favours random insertion of new wall material^8,9 However, dispersion of surface components after incorporation could mask a localised pattern of insertion^5,10,11. To try to distinguish between the two possible modes of insertion we have investigated the pattern of cell wall segregation in a mutant of Bacillus subtilis, which has a markedly slower cell wall turnover, so that it is possible to follow for much longer than with strains having normal, faster cell wall turnover¹². We report here a clear segregation of old and new wall, indicating localised insertion of material.