Biochemical Aspects of Competence in the Bacillus Subtilis Transformation System. I. Chemical Composition of Cell Walls.

Populations of Pneumococcus (1)) Haemophilus inJEuenxae (2)) and Bacillus subtilis (3, 4) develop the capacity to incorporate and to be modified genetically by deoxyribonucleic acid during the latter portion of the logarithmic phase of growth. In 1946 McCarty, Taylor, and Avery (5) suggested that this rapid development of sensitivity to transforming DNA might be related to a reversible alteration of the surface of pneumococcal cells by an enzyme which would make possible the absorption or penetration of DNA. Since the development of sensitivity to transforming DNA or competence in B. subtilis required a period of unbalanced growth and was inhibited by excessive amounts of cell wall precursors, Spieizen (3) also postulated that an alteration of the cell wall might be necessary for the development of competence in this transformation system. Recent studies have indirectly supported this hypothesis. For instance, the poorly transformable mutant strains of B. subtilis isolated to date do not incorporate DNA irreversibly (6). However, if the DNA was introduced by a phage (transduction) the frequency of genetic modification was similar in both the poorly and highly transformable strains (7, 8). Finally, protoplasts of Xhigella paradysenteriae (9) and Escherichia coli (10-12) but not intact bacteria can be infected by phage DNA. This morphological and chemical study was initiated in order further to investigate the role of the cell wall in competence. The evidence presented below demonstrates that there are quantitative chemical differences between cell walls obtained from poorly and highly transformable strains of B. subtilis.