Anti-Biofilm Ability Of Garlic Extract On Pantoea Agglomerans And Application To Biosand Filter

A biosand filter (BSF) is used as one of the appropriate technology to get purified water in waterpoor countries and developing countries. BSF purifies water to the level of cleanness necessary to be used in daily life and is widely used worldwide, especially given its producibility and simplicity. However, there is a circumstance that pathogens may be included in the formation of schmutzdecke (biofilm) that helps with internal water purification. The environment may be exposed to the pathogens located inside the BSF, causing complications. Pantoea agglomerans found in the biofilm of the BSF were selected as an opportunistic pathogen, and research was conducted to identify and inhibit the biofilm formation of opportunistic pathogens. The natural substances used to inhibit the biofilm formation were garlic extract and moss extract. Moreover, indole, which acts as a signaling molecule in microbes, was also used as a control. The biofilm growth curve of P. agglomerans in vitro was measured and the biofilm formation inhibition abilities of indole and natural extract were confirmed. Subsequently, genes related to biofilm formation and quorum sensing, a method of bacterial communication, were selected, and their expression levels were compared in relation to each other. BSF was produced and applied in an actual filter and water was poured in for 4 weeks to form biofilm. Garlic extract and moss extract were added to each filter, and the gene expressions and colony-forming unit (CFU) counts of the biofilm layer, effluent water, and the source water were compared. Furthermore, 16S rRNA sequencing was carried out. Indole and garlic treatment groups inhibited biofilm formation by 85.37% and 76.99% respectively and when incubated for 18 h, the biofilm formation was reduced to as low as 20%. Each treatment significantly affected gene expression in indole and garlic treatment groups: in both groups, pagI/R was reduced; in the indole treatment group only, bssS increased; and in both groups, ompW increased only at the early stages of biofilm formation. Indole and garlic treatment group's pagI/R increased in correlation to the duration of incubation. Moss-treated group inhibited biofilm formation rates, CFU counts, and gene expression levels, but to a lower extent than the other groups. P. agglomerans biofilm was inhibited by garlic or indole. The application on the actual filter confirmed the antibacterial effect and anti-biofilm effects of garlic and that the total variety of microbes was also reduced.