Meilin Li,Liya Xiong,Wenhan Chen,YiSha Li,Abdullah Khan,Charles A. Powell,Baoshan Chen,Muqing Zhang
Xanthomonas albilineans (Xal) is a gram-negative bacterial pathogen responsible for developing sugarcane leaf scald disease, which engenders significant economic losses within the sugarcane industry. In the current study, homologous recombination exchange was carried out to induce mutations within the virB/D4 -like type IV secretion system (T4SS) genes of Xal. The results revealed that the virB11 -deletion mutant (Δ virB11 ) exhibited a loss in swimming and twitching motility. Application of transmission electron microscopy analysis further demonstrated that the Δ virB11 failed to develop flagella formation and type IV pilus morphology and exhibited reduced swarming behaviour and virulence. However, these alterations had no discernible impact on bacterial growth. Comparative transcriptome analysis between the wild-type Xal JG43 and the deletion-mutant Δ virB11 revealed 123 differentially expressed genes (DEGs), of which 28 and 10 DEGs were notably associated with flagellar assembly and chemotaxis, respectively. In light of these findings, we postulate that virB11 plays an indispensable role in regulating the processes related to motility and chemotaxis in Xal.
Meilin Li,Cuilin Huang,Liya Xiong,Xiao Yang,Charles A. Powell,Ronghui Wen,Muqing Zhang
Sugarcane leaf scald, caused by Xanthomonas albilineans , is a significant bacterial disease that poses a substantial threat to global sugar production. The quorum-sensing (QS) system in X. albilineans presents a promising target for anti-virulence strategies. Here, we demonstrate that penicillic acid exhibits potent antibacterial activity against X. albilineans , with a minimum inhibitory concentration (MIC) of 6 μg/mL and an effective concentration for 50 % inhibition (EC₅₀) of 3.703 μg/mL. Transcriptome analysis, molecular docking, and surface plasmon resonance (SPR) confirmed that penicillic acid competitively binds the sensory histidine kinase RpfC, disrupting DSF-mediated QS signaling. At sub-inhibitory concentrations (½ MIC), penicillic acid significantly suppressed twitching, swimming, and swarming motility by downregulating genes associated with type IV pili, flagellar assembly, and chemotaxis. At full MIC, direct binding of penicillic acid to the FlgE and CheW proteins further impaired motility. These findings elucidate the molecular mechanism of penicillic acid and support its potential as a quorum-sensing inhibitor for biocontrol of sugarcane leaf scald.
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