Observations on biofilm bacteria isolated from aluminium panels immersed in estuarine waters

Microfouling biomass generally increased on aluminium panels immersed in the surface waters of a tropical estuary over a period of 30 d. A hundred bacterial colonies were randomly isolated, purified and morphologically, physiologically and biochemically characterised. There was an obvious difference in colony morphology during the period of immersion. Most of the colonies were motile, catalase and oxidase positive Gram negative rods. Pseudomonas was the most abundant initial colonizer during the first 24 h following immersion, and Flavobacterium and Alkaligenes were common throughout the immersion period. Representatives of the Enterobacteriaceae were present only during the first 7 d after immersion. Vibrio was the most predominant organism and its abundance generally increased over the period of immersion. Alkaligenes exhibited a decreasing trend over the 22 d immersion period followed by an increase in abundance at day 30 after immersion. However, no particular trend was observed for Flavobacteria.

The isolates were screened for their cell surface hydrophobicity using the BATH method. Most of the isolates were hydrophilic. However, as the period of immersion increased there was a relative increase in cell surface hydrophobicity of the isolates.