Isolation and identification of early marine biofilm-forming bacteria on commercial paint surface

Aims: To investigate early marine biofilm-forming bacterial diversity on immersed antimicrobial-free commercial paint substratum in seawater. Methodology and results: Total ten bacterial strains were successfully isolated and identified by complete 16S rRNA sequencing. The isolates morphological, biochemical properties, biofilm-forming ability, extracellular polymeric substance (EPS) productivity and components were characterised. The morphological and biochemical characterization of the strains showed strains-specific variation. All isolates were strong biofilm producers with four motile strains being both flat-bottom and air-liquid-interface biofilm producers, while other strains were only air-liquid interface biofilm producer. Based on 16S rRNA, three strains were identified as Marinomonas communis, two were Marinomonas sp., while the rest were Alteromonas litorea, Alteromonas sp., Salinimonas lutimaris, Idiomarine baltica and Bacillus niabensis. The amount of EPS that the isolates produced ranged from 1.95 to 2.89 g/L and productivity of EPS was inversely correlated with the cell biomass. Analysis of the extracted EPS using attenuated total reflectance- fourier transform infrared (ATR-FTiR) showed that all isolates EPS contained carbohydrates, nucleic acid, protein, DNA/RNA and lipid. Conclusion, significance and impact of study: Bacterial diversity in early stages of biofilm on the commercial paint surface was dominated by Gram-negative bacteria from Gammaproteobacteria class. Isolates with superior cell growth showed lowest EPS production. This finding was expected to provide knowledge on distribution of different marine bacterial species in the biofilm on paint coated surfaces which may beneficial to formularize a new antibiofilm paint additive.