Characterization of a catalase-deficient mutant of Xanthomonas axonopodis pv. citri

MARÍA LAURA TONDO; SILVANA PETROCELLI; JORGELINA OTTADO; ELENA G. ORELLANO

Tucuman Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Xanthomonas axonopodis pv. citri (Xac) is a Gram-negative obligate aerobic bacterium that infects citrus plants. Pathogenic bacteria are usually exposed to H2O2 produced either by normal aerobic metabolism or as a part of the plant defense response against microbial invasion. In order to survive and colonize plant tissues Xac must overcome H2O2 toxicity, and catalases are enzymes employed for its detoxification. We have previously shown that KatE is the major catalase induced in Xac during the stationary phase of growth and in the XVM2 medium, suspected to mimic the environment of plant intercellular spaces. In this study, a XackatE mutant strain was generated by insertional mutagenesis and was genetically verified. The effect of katE disruption on the catalase pattern was assessed by native gel electrophoresis and catalase staining, demonstrating the absence of an upper, slow-migrating band present in wild-type cells. In contrast to wild-type bacteria, no induction of total catalase activity was observed in the stationary phase cultures of the XackatE mutant. Furthermore, the mutant strain was more sensitive to H2O2 treatment, the difference of survival being more pronounced during the stationary phase. Finally, the katE mutant was assayed in planta during host and non-host interactions, revealing a novel role for KatE during the establishment of plant disease.