Thiobacillus spp.
- Thiobacillus thiooxidans: Acidophilic, chemolithoautotrophic, and efficient in oxidizing elemental sulfur and sulfide to sulfuric acid, especially in acidic environments.
- Thiobacillus ferrooxidans (now reclassified as Acidithiobacillus ferrooxidans): Known for its role in sulfur and iron oxidation; common in mining environments where it drives bioleaching and accelerates corrosion.
Acidithiobacillus spp.
- Acidithiobacillus thiooxidans: Capable of oxidizing sulfur and contributing to severe acidification, especially in environments with low pH.
- Acidithiobacillus caldus: Highly thermophilic and acidophilic, oxidizes sulfur compounds in high-temperature, low-pH settings.
Beggiatoa spp.
- Filamentous sulfur-oxidizing bacteria often found in marine and sulfur-rich environments. Known to produce sulfuric acid in anaerobic environments, contributing to “sulfide corrosion.”
Thiomicrorhabdus spp. (formerly Thiomicrospira)
- Marine sulfur-oxidizing bacteria found in high-sulfide, low-oxygen environments, such as deep-sea vents, that contribute to the biocorrosion of submerged structures.
Desulfovibrio spp. (secondary involvement)
- Though primarily sulfate-reducing, some species can contribute indirectly to corrosion by producing H₂S, which then serves as a substrate for sulfur-oxidizing bacteria, accelerating corrosion in a consortia.
Paracoccus spp.
- Paracoccus pantotrophus: Known for its sulfur-oxidizing capabilities and presence in wastewater and biofilm environments, where it can contribute to sulfuric acid production and infrastructure corrosion.
Pseudomonas spp.
- Some species within the Pseudomonas genus can oxidize sulfur under specific conditions. Although not exclusive sulfur oxidizers, they are often found in sulfur-rich environments and can contribute to corrosion in wastewater systems.
Starkeya novella
- A facultative sulfur-oxidizing bacterium capable of oxidizing thiosulfate to sulfate, commonly found in soil and sometimes in wastewater environments.
Sulfur-Oxidizing Archaea Associated with Corrosion
Acidianus spp.
- Acidianus brierleyi: A thermophilic sulfur-oxidizing archaeon found in hot, acidic environments such as geothermal vents; oxidizes sulfur and contributes to bioleaching and corrosion.
Sulfolobus spp.
- Sulfolobus acidocaldarius and Sulfolobus metallicus: Extreme thermophiles and acidophiles that oxidize sulfur in environments like hot springs and geothermal sites. Known to contribute to corrosion in high-temperature, acidic conditions.
Metallosphaera spp.
- Metallosphaera sedula: Known for sulfur and metal oxidation, commonly found in acid mine drainage and other sulfur-rich environments; contributes to corrosion in acidic conditions by producing sulfuric acid.
Thermoplasma spp.
- Thermoplasma acidophilum: Lacks a cell wall and thrives in extremely acidic environments, oxidizing sulfur compounds and contributing to acid production, often found in hot, acidic environments that accelerate corrosion processes
Environmental Contexts of SOB and SOA in Corrosion
These bacteria and archaea are commonly found in:
- Acid Mine Drainage (AMD): Where sulfide minerals are exposed to oxygen and water, creating ideal conditions for SOB and SOA.
- Wastewater Treatment Plants: Specifically in pipes and systems where hydrogen sulfide accumulates and leads to anaerobic corrosion.
- Marine and Submerged Structures: Areas rich in sulfur compounds and low oxygen levels, like subsea pipelines and ship hulls.
- Industrial Cooling and Water Systems: Where warm, nutrient-rich water can harbor microbial biofilms that include SOB, leading to sulfuric acid production and bio-corrosion.
These SOB and SOA, particularly when in consortia with sulfate-reducing bacteria (SRB), can form biofilms that enhance corrosion, posing significant challenges in many industrial and natural environments.
