Shewanella purefaciens

In this study, [95] model anaerobic corrosion of iron without the involvement of hydrogen. They postulate that the SRB that grow in very close contact with the iron surface can take electrons directly from the metal surface (in a slept they call electron pick-up ) and transfer these electrons to the sulphate-reducing system (SRS). While this proposed mechanism is certainly a breakthrough, there are still serious questions to be answered. For example, it is unknown how the electron pick-up step works and what mechanisms are involved there. As we will see later. Little et al. [32] have also demonstrated that for another group of bacteria which are important in corrosion (i.e., Shewanella purefaciens which are iron-reducing bacteria), the reduction of metal requires contact between the cell and the surface where the reduction rate is directly related to the surface area. The same researchers also found that the location of pits induced by these bacteria on carbon steel coincided with sites of bacterial colonisation. 

Most of the IRB are fermentators under anaerobic conditions, however, there are a few that actually need ferric iron under anaerobic conditions [112]. To add more into the complex picture, some of the IRB can use nitrate for anaerobic respiration [112]. Little et al. reported that IRB such as Shewanella purefaciens can use oxygen, Fe(III), Mn(lV), NOj, NOj, S2O3", SO3" and others [32]. The same researchers also reported that S. purefaciens under aerobic and anaerobic conditions may or may not use the same material (e.g., acetate that can be used aerobically but not anaerobically). Perhaps Panter is right in his recommendation that oxygen content [for IRB] is more important in determination [of their] numbers than available ferric ion content [112]. 

On the other hand. Little et al., who did not use polarisation methods but instead one of the safest electrochemical methods, electrochemical noise analysis (to be discussed later in Chapter 6) reported the corrosion-enhancing effects of another type of IRB, Shewanella purefaciens [32]. 

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See also in sourсe #XX -- [ ]

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