The LCP Family Protein, Psr, Is Required for Cell Wall Integrity and Virulence in Streptococcus agalactiae

A robust cell envelope is the first line of protection for an infecting pathogen when encountering the immune defense of its host. In Gram-positive organisms, LytR-CpsA-Psr (LCP) family proteins play a major role in the synthesis and assembly of the cell envelope. While these proteins could be considered for potential new drug targets, not enough is known about how they function to support the integrity of the cell wall. Streptococcus agalactiae (group B streptococcus or GBS) is known to encode at least three LCP family proteins, including CpsA, LytR (BrpA) and Psr. Using strains of GBS that have mutations in two of the three LCP proteins, we were able to determine a role for these proteins in GBS cell wall integrity. The results presented here demonstrate that the absence of Psr results in a decreased growth rate, decreased viability over time, inconsistent cocci morphology and diminished cell wall integrity, as well as an increased penicillin susceptibility, decreased capsule levels and attenuation in virulence in a zebrafish model of infectious disease. A strain that is missing two of the LCP family proteins, CpsA and Psr, exhibits an increase in these defective phenotypes, indicating that CpsA and Psr are partially redundant in function.

Automated summary

A robust cell envelope is crucial for pathogens to protect themselves from the immune defense of their host. In this study, the role of LytR-CpsA-Psr (LCP) family proteins in the synthesis and assembly of the cell envelope in Streptococcus agalactiae (GBS) was investigated. The results showed that the absence of Psr led to decreased growth rate, viability, consistent cocci morphology, and cell wall integrity, as well as increased susceptibility to penicillin and attenuation in virulence. These findings indicate that Psr, along with CpsA, plays a partially redundant role in supporting GBS cell wall integrity.