Investigating Polyhydroxyalkanoate Synthesis for Insights into Drug Resistance in Xanthomonas oryzae pv. oryzae

Polyhydroxyalkanoates (PHAs), synthesized by <i>Xanthomonas</i> to endure adverse conditions, are primarily regulated by the critical genes <i>phaC</i> and <i>phaZ</i>. Poly-3-hydroxybutyrate (PHB), a common polyhydroxyalkanoate (PHA), has been implicated in metabolism, pathogenicity, and various physiological processes in <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> (<i>Xoo</i>). In this study, we investigated the effects of HN-2 using n-butanol extract (HN-2 n-butanol extract) derived from <i>Bacillus velezensis</i> on <i>Xoo</i>. The results showed that HN-2 n-butanol extract could induce PHB accumulation in <i>Xoo</i>, potentially via surfactin. Moreover, examination of drug resistance, pathogenicity, and morphological characteristics of <i>Xoo</i> revealed PHB played a significant role in the drug resistance, pathogenicity, membrane integrity, and growth rate of <i>Xoo</i> strains following the deletion of <i>phaZ</i> and <i>phaC</i>. The ∆<i>phaZ</i> strain was the most significant, with a growth rate reduced to 58.19% of the <i>PXO99^A</i> at 36 h and an inhibition zone 57.46% larger than that of <i>PXO99^A</i> by HN-2 n-butanol extract. Transmission electron microscopy further revealed blank spots in <i>Xoo</i> after treatment, with the fewest spots observed in ∆<i>phaZ</i>, indicating its impaired ability to repair and maintain membrane integrity. These findings offer valuable insights that could serve as a foundation for elucidating the mechanisms of drug resistance and future research on preventing <i>Xoo</i>-induced diseases.