Echenique, J. | Search bioRxiv

bioRxiv2026

GpoA Glutathione Peroxidase Links Oxidative Stress Response, Antibiotic Persistence, and Virulence in Streptococcus pneumoniae

Glutathione (GSH) peroxidases are conserved enzymes found in prokaryotic and eukaryotic organisms that reduce H2O2 to protect cells from oxidative stress damage. In this study, we identified and characterized the GpoA glutathione peroxidase of S. pneumoniae, one of the most important human bacterial pathogens. This bacterium is unable to synthesize endogenous GSH as a cofactor for this enzyme but acquires GSH from host tissues via the GshT transporter. We demonstrated that recombinant GpoA exhibits GSH peroxidase activity and that the Cys36 residue is essential for this function. The gpoA transcripts, as well as tpxD and ahpD, which encode the TpxD thiol peroxidase and the AhpD alkylhydroperoxidase, respectively, were upregulated when pneumococci were exposed to H2O2. The{Delta} gpoA, {Delta}tpxD, {Delta}ahpD, and{Delta} gshT mutants exhibited increased susceptibility to H2O2, and also impaired intracellular survival in pneumocytes, macrophages, and neutrophils compared to the wild-type strain. These findings indicate that GpoA, TpxD, and AhpD constitute a robust H2O2 detoxification system that depends on extracellular GSH uptake. These three peroxidases also contribute to the fluoroquinolone persistence mechanism, which is closely associated with the oxidative stress response in S. pneumoniae. Additionally, we investigated the effect of GpoA on virulence in a murine model. The {Delta}gpoA mutant exhibited diminished survival across multiple organs relative to the wild-type strain, suggesting that GpoA contributes to pneumococcal pathogenesis. The molecular, biochemical, and functional analysis of GpoA elucidates an effective bacterial mechanism that incorporates the TpxD and AhpD peroxidases alongside the GshT transporter, promoting extracellular and intracellular survival under oxidative stress conditions.

microbiology↗

bioRxiv2019

The pneumococcal two-component system VisRH is linked to enhanced intracellular survival of Streptococcus pneumoniae in influenza-infected pneumocytes

The virus-bacterial synergism implicated in secondary bacterial infections caused by Streptococcus pneumoniae following infection with epidemic or pandemic influenza A virus (IAV) is well documented. However, the molecular mechanisms behind such synergism remain largely ill-defined. In pneumocytes infected with influenza A virus, subsequent infection with S. pneumoniae leads to enhanced pneumococcal intracellular survival. The pneumococcal two-component system VisRH appears essential for such enhanced survival. Through comparative transcriptomic analysis between the {Delta}visR and wt strains, a list of 179 differentially expressed genes was defined. Among those, the clpL protein chaperone gene and the psaB Mn+2 transporter gene, which are involved in the stress response, are important in enhancing S. pneumoniae survival in influenza-infected cells. The {Delta}visR, {Delta}clpL and {Delta}psaB deletion mutants display increased susceptibility to acidic and oxidative stress and no enhancement of intracellular survival in IAV-infected pneumocyte cells. These results suggest that the VisRH two-component system senses IAV-induced stress conditions and controls adaptive responses that allow survival of S. pneumoniae in IAV-infected pneumocytes.\n\nAuthor summaryS. pneumoniae is an inhabitant of the human nasopharynx that is capable of causing a variety of infections contributing to an estimated 1.6 million deaths each year. Many of these deaths occur as result of secondary S. pneumoniae infections following seasonal or pandemic influenza. Although S. pneumoniae is considered a typical extracellular pathogen, an intracellular survival mechanism has been more recently recognized as significant in bacterial pathogenesis. The synergistic effects between influenza A and S. pneumoniae in secondary bacterial infection are well documented; however, the effects of influenza infections on intracellular survival of S. pneumoniae are ill-defined. Here, we provide evidence that influenza infection increases S. pneumoniae intracellular survival in pneumocytes. We demonstrate that the poorly understood VisRH signal transduction system in pneumococcus controls the expression of genes involved in the stress response that S. pneumoniae needs to increase intracellular survival in influenza A-infected pneumocytes. These findings have important implications for understanding secondary bacterial pathogenesis following influenza and for the treatment of such infections in influenza-stricken patients.

microbiology↗