N-acetylcysteine, a biofilm disruptor, formulated as a layered nanomaterial for the control of bacterial wilt in tomato

Bacterial wilt (BW), caused by Ralstonia solanacearum, persists as a constraint to tomato production in many geographical regions, particularly in the tropics. One potential strategy that can reduce crop losses due to BW is the use of effective chemical compounds in the target tissue, xylem, to disrupt biofilm formation. Nanomaterials that can be functionalized may be an option to achieve this goal. N-acetylcysteine (NAC) has antibacterial and biofilm disruption activities. Thus, the objective of this work was to investigate the effects of NAC and a NAC-based layered nanomaterial (Zn-Al layered double hydroxide intercalated with N-acetylcysteine) on R. solanacearum cell viability, formation of bacterial biofilm, phytotoxicity to tomato plants, and the severity of BW under greenhouse conditions. R. solanacearum was grown in LB medium. Bacterial growth was assessed when exposed to 0.25, 0.50, 0.75, and 1.0 mg of NAC mL^‑1. Cell viability was evaluated by serial dilution and quantification of the CFU. Inhibition of biofilm formation was assessed using the 1% crystal violet assay. The disease index was determined in 'Santa Cruz' plants treated by either root dipping or seed imbibition with NAC and sown in infested soil. Bacterial cell viability was reduced completely and biofilm formation was prevented with 0.75 or 1 mg of NAC mL^‑1. The progress of the BW in terms of increasing disease severity was delayed by 7 days. There was no effect on germination of seeds treated with NAC up to 5 mg of NAC mL^‑1. However, phytotoxicity was observed in seedlings treated by root dipping. NAC-based nanomaterial may be useful to reduce severity of BW and/or to complement quantitative resistance in tomato varieties.