Effects of LytR on bacterial morphology in Streptococcus pyognes

A robust cell envelope is the first line of defense in infectious pathogens when encountering host immune defenses. In Gram-positive bacteria, LytR-CpsA-Psr (LCP) family proteins play a major role in the synthesis and assembly of the cell envelope. The Gram-positive bacterium S. pyogenes causes a wide range of diseases from pharyngitis to septicemia, but the involvement of LytR in the synthesis and assembly of the cell wall envelope in this bacterium is not clear. Therefore, we investigated whether LytR of S. pyogenes, like LytR of other streptococci, is involved in cell wall formation. The lytR gene-deficient strains were used to investigate the bacteria's ability to form a chaining, drug sensitivity to penicillin G, an inhibitor of cell wall synthesis, bacterial biofilm formation, and the morphological structure of bacteria by transmission electron microscopy, and the expression of pbp2b, which encodes a penicillin-binding protein, compared with the wild-type strain. Our results showed that LytR-deficient strains had reduced bacterial chaining compared to wild-type strains. Compared to wild-type strains, LytR-deficient strains were also more drug sensitive to the cell wall synthesis inhibitor penicillin G. This genetic study was accompanied by increased expression of the pbp2b gene in the LytR-deficient strains. In addition, the LytR-deficient strain showed a reduced ability to form biofilms, and the lytR gene-deficient strain showed morphological irregularities with abnormal bacterial septa. These results indicate that the lytR gene is involved in cell wall synthesis in S. pyognes.