Both bacterial growth and corrosion involve electrochemical (charge-transfer) half-cell reactions which have been conveniently compared on the potential-ps (Pourbaix) diagram in this paper. We have tabulated bacteria which mediate or facilitate various pairs of these half-cell reactions in otherwise kinetically unfavorable electrochemical cells. The tabulated electrochemical cells cover the range of microbial physiology from oxidizing (aerobic) to reducing (anaerobic) conditions and from acidic to neutral and alkaline pH on the Pourbaix diagram. Correlations emerging from Pourbaix plots of microbially affected half-cell reactions are discussed in relation to general microbial ecology and specifically to their influence on the corrosion of iron and carbon steel.