Polyamine-mediated mechanisms contribute to oxidative stress tolerance in Pseudomonas syringae

Abstract

Bacterial phytopathogens living on the surface or within plant tissues may experience oxidative stress because of the triggered plant defense responses. Although it has been suggested that polyamines can defend bacteria from this stress, the mechanism behind this action is not entirely understood. In this study, we investigated the effects of oxidative stress on the polyamine homeostasis of the plant pathogen Pseudomonas syringae and the functions of these compounds in bacterial stress tolerance. We demonstrated that bacteria respond to H2O2 by increasing the external levels of the polyamine putrescine while maintaining the inner concentrations of this compound as well as the analogue amine spermidine. In line with this, adding exogenous putrescine to media increased bacterial tolerance to H2O2. Deletion of arginine decarboxylase (speA) and ornithine decarboxylate (speC), prevented the synthesis of putrescine and augmented susceptibility to H2O2, whereas targeting spermidine synthesis alone through deletion of spermidine synthase (speE) increased the level of extracellular putrescine and enhanced H2O2 tolerance. Further research demonstrated that the increased tolerance of the ΔspeE mutant correlated with higher expression of H2O2-degrading catalases and enhanced outer cell membrane stability. Thus, this work demonstrates previously unrecognized connections between bacterial defense mechanisms against oxidative stress and the polyamine metabolism.

Thermal and salt stress effects on the survival of plant growth‐promoting bacteria Azospirillum brasilense in inoculants for maize cultivation

“…The decrease in bacterial growth rate during the application of sublethal stress is one of the main responses observed in species present in inoculant formulations 23 and it has been reported for several species, including Azospirillum formosense, Azospirillum lipoferum, Gluconacetobacter diazotrophicus, Pseudomonas putida, Pseudomonas protegens, Pseudomonas aeruginosa, Rhizobum tropici, Rhizobium gallicum, Mesorhizobium ciceri, Mesorhizobium mediterraneum, Sinorhizobium meliloti, Bacillus endophyticus, Bacillus tequilensis and Burkholderia mesoacidophila. [34][35][36][37][38][39][40][41][42][43][44] Apparently, the application of sublethal stress affects the metabolism of bacterial cells, causing a steady state or slow growth. 45 Despite the decrease in the growth rate, both A. brasilense strains were able to survive under conditions of sublethal thermal and salt stress.…”

Urea Cycle of Bacillus thuringiensis Affects Its Survival under UV Stress

“…Arginase is involved in the synthesis of many secondary metabolites, such as ornithine, proline, and polyamines, as well as most of these secondary metabolite pathways also require the participation of RocF . Some studies have shown that these metabolites have a positive effect on the cellular stress resistance in other species. − This seems to explain why rocF -deficient strains show little change in the arginine content but their stress resistance was decreased, that is, the loss of the rocF gene leads to the blockage of secondary metabolite synthesis. However, although arginine and its secondary metabolites were shown to have a positive effect on the stress tolerance in other species, whether they are the main cause for the decrease in stress tolerance in Bt after rocF / argG gene knockout needs to be verified by subsequent studies.…”

An ecological-evolutionary perspective on the genomic diversity and habitat preferences of the Acidobacteriota

“…Recently, [57] demonstrated a link between increasing intracellular concentration of polyamines and improved oxidative stress tolerance in Pseudomonas. A similar role for polyamine can be speculated in the NSPL classes.…”