Toxic influence of pristine and surfactant modified halloysite nanotubes on phytopathogenic bacteria

Halloysite nanotube (Hal nanotube) - a clay mineral nanomaterial, was surface modified using cationic, anionic and non-ionic surfactants - cetyl trimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and Tween 80 respectively. The pristine Hal nanotube and the three surfactant modified Hal nanotubes (SM-Hal nanotubes) were tested against three phytopathogenic bacteria Xanthomonas oryzae, Agrobacterium tumifeciens and Ralstonia solanacearum. In the present study, by performing various bacterial toxicity assays, it has been established that SM-Hal nanotubes had a higher killing efficiency of phytopathogenic bacteria than pristine Hal nanotube. The surfactant modifications improved the dispersion of the Hal nanotube and altered the physicochemical properties like grain size, particle diameter, surface charge and hydrophilicity, which consecutively enhanced the interaction and the toxic effects on phytopathogenic bacteria. SM-Hal nanotubes inhibited phytopathogenic bacteria at a lower minimum inhibitory concentration (MIC) as compared to the pristine Hal nanotube. Among the three SM-Hal nanotubes, CTAB-modified Hal nanotube effectively suppressed the growth, disrupted the cell membrane integrity, induced higher reactive oxygen species (ROS) production and inhibited the biofilm formation of all the three phytopathogenic bacteria followed by Tween 80-modified and SDS-modified Hal nanotubes. Hence, it is evident that these tailor made SM-Hal nanotubes, can be effectively used as potent clay mineral nanomaterials to control phytopathogenic bacteria.