Role of teichuronic acid in Bacillus licheniformis: defective autolysis due to deficiency of teichuronic acid in a novobiocin-resistant mutant

Abstract

nov-12, a novobiocin-resistant mutant of Bacillus licheniformis ATCC 9945, grows as long chains of cells, a characteristic of autolytic-deficient (Lyt-) mutants. Isolated walls from nov-12 autolyzed at a rate equal to 5% of that displayed by wild-type walls, thus confirming the Lyt- phenotype. Protein-free nov-12 walls displayed marked resistance to, and also failure to bind, added autolysin solubilized from wild-type walls. Comparison of isolated cell walls revealed a deficiency in teichuronic acid in the mutant. Lesser differences were observed in walls of this strain, including a reduction in galactose, an increase in the proportion of peptidoglycan, and small quantitative differences in peptidoglycan composition though the proportions of protein and teichoic acid were similar in walls of both strains. Autolytic sensitivity was studied in walls in which protein, teichoic acid, and teichuronic acid were removed successively by selective extraction procedures. Autolysis of wild-type walls was unaffected by removal or protein or teichoic acid, but teichuronic acid removal rendered wild-type walls as insensitive to autolysis as mutant walls had been throughout. Therefore, in this mutant, deficiency in teichuronic acid alone leads to the Lyt- phenotype and, hence, activity and binding of autolysin(s) are dependent upon teichuronic acid but not teichoic acid. Also, the potential rate of autolysis of cell walls in this organism was correlated with the proportion of teichuronic acid in the wall. The possible significance of these findings with respect to control of autolysis and cell separation is discussed.