Erwinia amylovora catalases KatA and KatG are virulence factors and delay the starvation-induced viable but nonculturable (VBNC) response

Summary The life cycle of the plant pathogen Erwinia amylovora comprises periods inside and outside the host in which it faces oxidative stress caused by hydrogen peroxide (H2O2) and other compounds. Sources of this stress are plant defences, other microorganisms and/or exposure to starvation or other environmental challenges. However, the functional roles of H2O2 neutralizing enzymes like catalases during plant-pathogen interactions and/or under starvation conditions in phytopathogens of the family Erwiniaceae or closely related families have not been yet investigated. In this work, the contribution of E. amylovora catalases KatA and KatG to virulence and survival in non-host environments was determined using catalase gene mutants and expression as well as catalase activity analyses. The participation of E. amylovora exopolysaccharides (EPS) in oxidative stress protection was also investigated. Our study revealed: a different growth phase regulation of each catalase, with an induction by H2O2 and host tissues; the significant role of E. amylovora catalases as virulence and survival factors during plant-pathogen interactions; the EPSs induction by H2O2 despite the fact that apparently they do not contribute to protection against this compound; and the participation of both catalases in the detoxification of the starvation-induced intracellular oxidative stress, favoring the maintenance of culturability and, hence, delaying the development of the VBNC response. This article is protected by copyright. All rights reserved.