Morphology of the surface coat and extracellular matrix of sulphidogenic biofilms enriched in sulphate-reducing bacteria involved in biocorrosion processes in the offshore oil extraction industry off Brazil's coast.

Abstract

Anaerobic sulphate-reducing bacteria (SRB) are among the most important microorganisms involved in industrial biocorrosion (7,11). Like other microorganisms, SRB attach to metal surfaces and develop firmly adherent biofilms, in which microcolonies of different bacterial species can grow, immersed in an extensive extracellular matrix (EM) of anionic polysaccharide nature (6, 7). This complex tissue-like structure influences many physiological parameters of microbial colonization, including rate of growth, nutrient concentration and resistance to biocides. The development of an adherent biofilm defines two phases in which SRB can appear: planktonic/swimming and sessile/adherent (7). Direct observations of bacteria growing in natural or industrial environments have shown that these cells are always surrounded by some form of glycocalyx or coat (6,15,16), both in the planktonic and in the sessile phase. As described for the petroleum industry of the North Sea (11), in Brazil, biocorrosion caused by SRB is also a serious problem, affecting marine offshore platforms operated by PETROBRAS. Mixed populations of anaerobic bacteria, rich in SRB, can be obtained from samplers installed in the water injection system of the platforms, at points with a suitable environment for

Ultrastructure of sulphidogenic biofilms rich in sulphate-reducing bacteria causing corrosion in the offshore oil extraction platforms off Brazil's atlantic coast.

“…The exopolysaccharide layer covering the biofilm creates a microenvironment that can protect bacteria from bacteriophages, antibiotics, biocides and surfactant agents (5). In another study, we observed that in SRB-enriched biofilms the morphology of the bacterial glycocalyx and of the associated extracellular matrix varied, depending on the nature of the bacterial population under study (planktonic or sessile) and on the growth medium used (9).…”