Silver Armor Against Bacteria: A Battle of Antimicrobial Effectiveness

For many farmers, there is a need to improve crop resistance to pathogenic organisms. The climate of Florida and hurricane-prone location promotes the spread of many crop pathogens making management difficult and expensive. Therefore, this study evaluates using a Do-It-Yourself, DIY, method to produce colloidal silver solutions that may be used as effective inhibitors of bacteria growth. The efficacy was compared across gram-negative and gram-positive bacteria species. Production of colloidal silver used an electric current from eight 9-volt batteries wired in series. The starting silver was a jewelry chain, approx. 98% silver, suspended in a container of distilled water. Treatment effects were compared to a commercially available silver solution (10K, ppm) as the positive control via the Kirby-Baur method. Each petri dish was divided into four quadrants, into which each had a treated cellulose square impregnated with a treatment solution. Treatments were: T1-10K ppm AgNp; T-2-5ppm AgNp, T3-3ppm AgNp; and positive control T4-blank water control. The dimensions of Zones of Clearance (ZOC) and the bacterial growth surrounding treated squares were analyzed. The experiment was replicated four times. Data analysis conducted using one-way ANOVA with post hoc separation of means using the T test and Tukeys HSD. The positive control solution was the most effective bactericide across all species, followed by Treatment-2 (5-ppm treatment), which caused ZOC in gram-negative species. Treatment-3, the 3ppm, did not significantly affect bacterial suppression, while activity at 5ppm suggests that simple home-based, DIY systems can produce low cost, bactericidal nano-silver solutions. In this experiment the bacterium that tested that is also beneficial to plants, R. rubrum, showed an increased tolerance to all silver treatments. Improving homemade, DIY, systems may provide low-cost treatment solutions against some bacteria species important to backyard agriculturists.