Differential roles for polyamines in the oxidative stress response of Pseudomonas syringae

SOLMI L; ROSSI FR; ROMERO FM; RUIZ OA; BACH-PAGES M; PRESTON G; GÁRRIZ A

Simposio; Young Microbiologists Symposium; 2020

Putrescine and spermidine are the main polyamines (PAs) found in bacteria. These compounds comprehend a family of small aliphatic molecules implicated in protein synthesis and regulation, DNA integrity and stress resistance. The contribution of PAs to oxidative stress tolerance in human pathogens such as Escherichia coli and Pseudomonas aeruginosa has been clearly documented, but their functions in the stress response activated by other types of bacteria have not been poorly explored. In this study, we unveiled an important role for PA homeostasis during the oxidative stress response in the phytopathogenic bacteria Pseudomonas syringae pv. tomato DC3000. WT cells exposed to sublethal concentrations of hydrogen peroxide induced the secretion of PAs but maintained their intracellular concentrations in similar levels as those found in non-treated cells, suggesting a role for extracellular PAs. In turn, pre-treatment with spermidine enhanced stress susceptibility, whereas putrescine-treatment had no effect on stress tolerance. In agreement with this, a double mutant in the speA and speC genes showing undetectable levels of putrescine showed higher stress susceptibility, but disruption of the spermidine biosynthetic gene speE enhanced stress tolerance. These results demonstrate contrasting roles played by PAs in the response to oxidative stress in this bacterial species.