DIRECT INVOLVEMENT OF AN EXTRACELLULAR COMPLEX PRODUCED BY A MARINE SULFATE-REDUCING BACTERIUM IN DETERIORATION OF STEEL

A thermostable polysaccharide-protein complex capable of accelerating the deterioration of mild steel was produced by a marine strain of sul fate-reducing bacterium of the genus Desulfovibrio, and partially puri fied using low-pressure chromatography. This complex induced pitting o f steel in oxic aqueous solution. The increase in the corrosion rate o f steel exposed to the complex, determined using linear polarization r esistance measurements, correlated with the inferred increase in produ ction of exopolymer during the stationary phase of Desulfovibrio growt h. Atomic absorption analysis confirmed that the complex caused rapid dissolution of iron from the steel surface, while light microscopy obs ervations demonstrated that the complex caused grain boundary and inte rcrystalline attack of the steel, which did not occur in control solut ions. The molecular mass of the corrosive complex, determined using ge lfiltration, was greater than 200 kD.