Thiobacillius Thioxidans: Produce Sulfuric Acid.
 
Thiobacillis Ferrooxidans: Oxidize Ferrous to Ferric.
 
Gallionella & Sphaerotilus: Oxidize Ferrous to Ferric.
Form Tubercles.
 
Pseudomonas: Can Reduce Ferric to Ferrous.
 
Fungi: Some Can Produce Organic Acids.

Desulfovibro: Promotes formation of Sulfide films. Affects Iron & Steel, Stainless Steels, Aluminum, Zinc & Copper Alloys.
 
Desulfotomaculum: Produces Hydrogen Sulfide Gas. Affects Iron & Steel, and Stainless Steels. Spore Former.
 
Desulfomonas: Produces Hydrogen Sulfide gas. Affects Iron & Steel.

Different bacteria can thrive in different parts of your fire sprinkler system and cause damage by the MIC process.
 
Dry Systems: Mainly aerobic conditions.
 
Wet Systems: Mainly anaerobic conditions.
 
Both Systems May Have Micro-Environments where both aerobic & anaerobic conditions exist.