Scanning electron microscope study of biofilm formation at different flow rates over metal surfaces using sulphate‐reducing bacteria

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Abstract
Sulphate‐reducing bacteria (SRB) are implicated in biocorrosion in the oil industry. SRB biofilm formation was studied on metal coupons under a static system (SS) and a dynamic system (DS), using mixed populations of bacteria recovered from samplers installed in the water injection systems of offshore platforms on Brazil's Atlantic coast. Adherent biofilms consisting of rod, vibrio, filamentous, spiral and coccoid‐shaped bacteria enmeshed in an extracellular polysaccharide matrix (EPM) formed over the coupon surfaces. Coupons subjected to SS, showed significant differences in the kinetics of biofilm formation, the nature of the initial adhesion process and the amount of EPM produced, compared with DS. After 4 h incubation, a reversible attraction of a large number of bacteria was observed under SS. However, by 24 h, true attachment of bacteria to the substrate had begun in both systems. Using DS, many more EPM elements were observed at given points in time. Biofilm maturation under DS showed a 6 days’ lead compared with SS, requiring respectively, 4 and 10 d incubation. Thus, it was concluded that dynamic culture conditions should be preferentially used in laboratory studies of biofilm formation.

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