CENSUS-MIC

Rapidly detect and quantify specific microbial populations and processes involved in Microbiologically Influenced Corrosion (MIC).

CENSUS employs a molecular microbiological method (MMM) called quantitative polymerase chain reaction (qPCR) for enumeration of specific microorganisms or genes encoding specific biological processes associated with MIC.  To elucidate the distribution, abundance, and functional interactions in corrosion-related microbial populations, MI offers CENSUS quantification of total bacteria and a variety of microbes commonly implicated in MIC including sulfate reducing bacteria (SRB), nitrate reducing bacteria (NRB), methanogens, and acid producing acetogens.

Evaluation of the microorganisms present within a system permits project managers to:

  • Quantify MIC bacteria and accurately assess corrosion potential
  • Evaluate the effectiveness of treatments and O&M measures
Target MI Code    Relevance / Data Interpretation
Total Eubacteria  EBAC MIC is initiated by growth of a biofilm on the material surface. Monitoring total bacteria provides a general measure for evaluating bacterial growth in the system.
Total Archaea ARC Archaea are another general group of single celled microorganisms which, like bacteria, can initiate and contribute to MIC. Depending upon types and environmental conditions, total archaea can outnumber total bacteria and be a more important factor in MIC.
Sulfate Reducing Bacteria APS Sulfate reducing bacteria (SRB) consume hydrogen, produce hydrogen sulfide and are the group of microorganism most commonly implicated in the pitting corrosion of various metals.
Sulfate Reducing Archaea SRA Sulfate reducing archaea consume hydrogen, produce hydrogen sulfide and have been implicated in MIC at elevated temperatures.
 Exopolysaccaride Production BCE Gene involved in the production of exopolysaccharide (EPS) and biofilm formation by some Burkholderia spp.
Methanogens MGN Methanogens utilize hydrogen for growth, can contribute to cathodic depolarization and can cause corrosion rates comparable to sulfate reducing bacteria.
Fermenting Bacteria
 FER Anaerobic bacteria produce organic acids and hydrogen.  Acid production can lead to localized drops in pH facilitating corrosion while hydrogen production can support growth of other MIC associated organisms including SRB.
Nitrate Reducing Bacteria DNF Increasingly, nitrate addition is being used to stimulate growth of nitrate reducing bacteria as a bioexclusion strategy to combat SRB-mediated reservoir souring and MIC. The qDNF assay quantifies target genes encoding enzymes responsible for a key step in biological nitrate reduction.
Archaeal Nitrite Reducing Bacteria ADNF Similar to the qDNF assay, qADNF quantifies the two types of nitrite reductase genes (nirS and nirK) found in archaeal organisms.
Acid Producing Bacteria  AGN Acetogenic bacteria are strict anaerobes that produce acetate from the conversion of H2-CO2, CO, or formate. Hydrogen mediated acetogenesis has been demonstrated in high pressure natural gas pipelines confirming the in situ activity of this bacterial group. Further, the presence of acetic acid is known to exacerbate carbon dioxide corrosion of carbon steel.
Acetic Acid Bacteria AAB Quantifies the alcohol dehydrogenase (adhA) genes from acetic acid bacteria (Acetobacter, Gluconobacter, and Komagataeibacter).  adhA catalyzes the oxidation of ethanol to acetic acid which can be a potential cause of corrosion.
Iron Oxidizing Bacteria FeOB Iron oxidizing bacteria are a group of microorganisms commonly implicated in metal deposition and tubercle formation.
Manganese Oxidizing Bacteria  MnOB Like iron oxidizing bacteria, manganese oxidizing bacteria are capable of making deposits of metal oxides.
Sulfur Oxidizing Bacteria  SOB Often aerobic bacteria oxidize sulfide or elemental sulfur producing sulfuric acid.  Commonly implicated in the corrosion of concrete.
Iron Reducing Bacteria (other)
 IRB Iron reducing bacteria reduce insoluble ferric iron to soluble ferrous iron potentially facilitating the removal of protective corrosion products formed on exposed iron alloy surfaces.  However, other studies have suggested that the actions of IRB can inhibit corrosion through a variety of mechanisms.  This assay targets iron reducing bacteria such as Deferribacter, Ferrimonas, Geopsychrobacter, Geothermobacter, Geothrix, Geovibrio, Geothermobacterium and Albidiferax.  Please note that Geobacter and Shewanella  are also common iron reducing bacteria which need to be ordered as separate assays.
Iron Reducing Bacteria (Geobacter) GEO Iron reducing bacteria reduce insoluble ferric iron to soluble ferrous iron potentially facilitating the removal of protective corrosion products formed on exposed iron alloy surfaces.  This assay targets a common iron reducing bacteria, Geobacter. 
Iron Reducing Bacteria (Shewanella) SHW Anaerobic bacteria which can utilize cathodic hydrogen as an energy source, reduce ferric iron and sulfite to ferrous iron and sulfide indicating that it can play a role in MIC.
Iron Reducing Archaea IRA Targets two genera of iron reducing archaea, Ferroglobus and Geoglobus.
Nitrogen Fixing Bacteria NIF Nitrogen fixation converts nitrogen gas into ammonia which can be assimilated by organisms.  Nitrogen fixation may become increasingly important in mature biofilms.
Ammonia Oxidizing Bacteria AOB Ammonia oxidation or nitrification produces nitric acid causing corrosion of concrete and natural stone.  Depending on alkalinity levels, nitrification in water systems can increase lead contamination and increase copper solubility.
Deinococcus spp.
DCS Genus of bacteria considered very efficient primary biofilm formers and therefore have been implicated in slime formation and biofouling.
Meiothermus spp.  MTS Like Deinococcus spp., Meiothermus spp. are efficient primary biofilm formers and frequently implicated in slime formation and biofouling.
Glycerol Utilizing Bacteria
GLK Microbial degradation of glycerol, a byproduct of biodiesel production from fats, leads to the generatoin of VFAs (lactic and propionic acid) both of which have been observed at high concentrations in diesel tanks.  VFA production can substantially reduce local pH and also supports the growth of other microbial groups commonly implicated in corrosion.  The GLK assay targets a key functional gene in glycerol uptake and utilization.

 

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