ULTRASTRUCTURE OF SULPHIDOGENIC BIOFILMS RICH IN SULFATE-REDUCING BACTERIA CAUSING CORROSION IN THE OFFSHORE OIL EXTRACTION PLATFORMS OFF BRAZILS ATLANTIC COAST

Microorganisms, especially sulphate-reducing bacteria (SRB), have long been implicated in metal corrosion in the petroleum industry. SRB can appear in planktonic or adherent forms, interacting with surfaces to produce thick, consortial biofilms. We carried out an uItrastructural investigation of biofilms and planktonic bacteria obtained from samplers on offshore platforms operated in southeast Brazil. A great variety of Gram-negative bacteria were observed. The surface coat and extracellular matrix of these cells stained strongly with ruthenium red, indicating their anionic character. Sessile bacteria were found to be enmeshed in an extensive extracellular matrix. The inner ultrastructure of sessile bacteria was characterized by vacuoles, inclusions and internal membranes. ESI analysis revealed the presence of corrosion products associated with the surface coat of these bacteria.