KatG, the bifunctional catalase of xanthomonas citri subsp. citri, responds to hydrogen peroxide and contributes to epiphytic survival on citrus leaves
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Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible for citrus canker. This bacterium is exposed to reactive oxygen species (ROS) at different points during its life cycle,
including those normally produced by aerobic respiration or upon exposition to ultraviolet
(UV) radiation. Moreover, ROS are key components of the host immune response. Among
enzymatic ROS-detoxifying mechanisms, catalases eliminate H2O2, avoiding the potential
damage caused by this specie. Xcc genome includes four catalase genes. In this work, we
studied the physiological role of KatG, the only bifunctional catalase of Xcc, through the
construction and characterization of a modified strain (XcckatG), carrying an insertional
mutation in the katG gene. First, we evaluated the involvement of KatG in the bacterial
adaptive response to H2O2. XcckatG cultures exhibited lower catalase activity than those of
the wild-type strain, and this activity was not induced upon treatment with sub-lethal doses
of H2O2. Moreover, the KatG-deficient mutant exhibited decreased tolerance to H2O2 toxicity compared to wild-type cells and accumulated high intracellular levels of peroxides upon
exposure to sub-lethal concentrations of H2O2. To further study the role of KatG in Xcc
physiology, we evaluated bacterial survival upon exposure to UV-A or UV-B radiation. In
both conditions, XcckatG showed a high mortality in comparison to Xcc wild-type. Finally,
we studied the development of bacterial biofilms. While structured biofilms were observed
for the Xcc wild-type, the development of these structures was impaired for XcckatG. Based
on these results, we demonstrated that KatG is responsible for Xcc adaptive response to
H2O2 and a key component of the bacterial response to oxidative stress. Moreover, this
enzyme plays an important role during Xcc epiphytic survival, being essential for biofilm formation and UV resistance.
Para citar este articulo: Tondo ML, Delprato ML, Kraiselburd I, Fernández Zenoff MV, Farías ME, Orellano EG (2016) KatG, the Bifunctional Catalase of Xanthomonas citri subsp. citri, Responds to Hydrogen Peroxide and Contributes to Epiphytic Survival on Citrus Leaves. PLoS ONE 11(3): e0151657. doi:10.1371/journal.pone.0151657
Para citar este articulo: Tondo ML, Delprato ML, Kraiselburd I, Fernández Zenoff MV, Farías ME, Orellano EG (2016) KatG, the Bifunctional Catalase of Xanthomonas citri subsp. citri, Responds to Hydrogen Peroxide and Contributes to Epiphytic Survival on Citrus Leaves. PLoS ONE 11(3): e0151657. doi:10.1371/journal.pone.0151657
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