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.