4. Antibacterial mechanism of nano-silica against potato late blight


Nanomaterials have certain toxicity to microorganisms and can therefore be used as antibacterial agents. Nano-chitosan and nano-copper particles can significantly inhibit the growth of a variety of microorganisms, with the minimum inhibitory concentration value being less than 0.25μg/ml. The antibacterial mechanism is that the positively charged chitosan particles interact with the negatively charged microbial cell membrane, causing cell membrane damage, increased permeability, and protein leakage, leading to microbial death. The main antibacterial mechanism of nanomaterials may be the production of some secondary products that cause microbial cell damage, such as reactive oxygen and heavy metal ions dissolved in the environment. They may also interact directly with cells, such as interrupting the transmembrane electron transfer process, destroying the outer membrane of the cell, and oxidizing the protein composition in the cell. When Phytophthora infestans is stressed by nano-silicon dioxide, the bacteria produce hydroxyl radicals OH, superoxide radicals 02- and singlet oxygen O, which lead to oxidative stress, DNA damage, increased intracellular MDA content, cell membrane structure destruction, leakage of contents, reduced respiration intensity, inhibition of bacterial physiological metabolism and even death. DCFH-DA staining of potato leaves sprayed with nano-silicon dioxide confirmed that the leaves did not produce reactive oxygen under stress, verifying the good biocompatibility between the two.