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

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