GROWTH-PHASE DEPENDENT RESISTANCE TO OXIDATIVE STRESS IN A PHYTOPATHOGEN XANTHOMONAS-ORYZAE PV ORYZAE

Xanthomonas oryzae pv. oryzae, a rice bacterial pathogen, showed growt h phase dependent resistance to oxidative stress billing. Stationary p hase cells were much more resistant to killing concentrations of H2O2, organic peroxides, and a superoxide generator (menadione) than cells from early log and mid-log phases. The stationary phase stress resista nce phenotype did not require de novo protein synthesis. Also, nutrien t starvation or media metabolites were not inducing signals for the ph enotype. The stationary phase stress resistance did not apply to all t ypes of stress. For example, X. oryzae pv. oryzae was equally sensitiv e to heat and pH 5.5 stress at all growth phases tested. This pattern of stationary phase resistance to stress differs from observations in other bacteria and could be important in plant-microbe interactions.