Effects of anti-fouling paints on marine bacterial biofilm development

Biofilm bacteria can cause several problems in marine infrastructures. The goal of the research was to isolate and identify biofilm bacteria that produce extracellular polymeric substance (EPS) on static panels and to determine minimum inhibitory concentrations (MICs) of the antifouling agents preventing the growth of biofilm bacteria. Zinc oxide, copper oxide, tributyltin, fluorine, triazine diamine based additives and one type rustproof paint were used as the antifouling agents in the paints. Bacterial growth was detected on all test panels coated by each of the antifouling paints during the sampling period in the two marinas located at the Izmir region. One hundered twenty strains isolated from the test panels were cultured, and a total of twenty unique strains were selected for further characterization using biochemical and molecular methods. Phylogenetic analysis using rDNA sequences indicated that the twenty strains belonged to the ?-Proteobacteria subclass and Firmicutes subclass (Pseudoalteromonas, Alteromonas, Klebsiella, Vibrio, and Exiguobacterium). Eight isolates were selected for further study based on their EPS-producing ability and sugar and protein contents of the EPS. Cell growth and EPS productivity were found to be negatively correlated. Sugar composition of EPS were determined by thin layer choromatography (TLC). It was observed that of these polysaccharides contained glucose, galactose, fructose and rhamnose. The paint, which contains triazine diamine and copper oxide, showed strong antibacterial activity against each individual strains in the MIC test. It was observed that while biofilm bacteria were very sensitive to antifouling paints, they were able to gain resistance following the development of biofilm. Additionally, physico-chemical parameters of seawater and viable bacteria counts displayed relations during the study period. However, it was not found any strong correlation between viable bacteria density and nutrient concentrations.