Arginine Decarboxylase Is Essential for Pneumococcal Stress Responses.

Polyamines such as putrescine, cadaverine, and spermidine are small cationic molecules that play significant roles in cellular processes, including bacterial stress responses and host-pathogen interactions. is an opportunistic human pathogen, which causes several diseases that account for significant morbidity and mortality worldwide. As it transits through different host niches, is exposed to and must adapt to different types of stress in the host microenvironment. We earlier reported that TIGR4, which harbors an isogenic deletion of an arginine decarboxylase (Δ), an enzyme that catalyzes the synthesis of agmatine in the polyamine synthesis pathway, has a reduced capsule. Here, we report the impact of arginine decarboxylase deletion on pneumococcal stress responses. Our results show that is more susceptible to oxidative, nitrosative, and acid stress compared to the wild-type strain. Gene expression analysis by qRT-PCR indicates that thiol peroxidase, a scavenger of reactive oxygen species and from the arginine deiminase system, could be important for peroxide stress responses in a polyamine-dependent manner. Our results also show that is essential for endogenous hydrogen peroxide and glutathione production in . Taken together, our findings demonstrate the critical role of arginine decarboxylase in pneumococcal stress responses that could impact adaptation and survival in the host.