Glossary of Terms

Total Bacteria	A summary count of all the bacteria in a sample
Total archaea	A summary count of all the archaea in a sample.
Quality Controls	Internal DNA controls are used to ensure accurate and precise qPCR quantification
Sulfate reducing bacteria	Sulfate reducing bacteria (SRB) gain energy for growth by reducing sulfate(SO42-) to sulfide (H2S). Sulfide production can cause souring of a system SRB can also cause MIC by directly removing electrons from steel surfaces, and indirectly by producing corrosive by-products such as sulfide which react with iron to produce iron sulfide (FeS) deposits.
Methanogens	These anaerobic Archaea produce methane during their metabolism Can lead to MIC by removing electrons directly from steel surfaces or indirectly through syntrophic interactions with other microbes
Iron oxidizing bacteria	Iron oxidizing bacteria (IOB) gain energy for growth by oxidizing ferrous iron (Fe2+) to ferric iron (Fe3+), resulting in the formation of ferric iron oxides on the steel surface These oxides can be a protective physical barrier preventing any further corrosion, however they also result in the formation of oxygen depleted zones leading to electrochemical alterations of the steel surface, and localized, pitting corrosion
Iron reducing bacteria	Iron reducing bacteria (IRB) gain energy for growth by reducing ferric iron (Fe3+) to ferrous iron (Fe2+) Fe3+ reduction can remove protective oxide coatings, exposing the surface beneath to further corrosion
Thiosulfate reducing bacteria	A sulfide producing microbe, increasingly common to oil and gas reservoirs stimulated by hydraulic fracturing methods Sulfide production occurs via the use of thiosulfate and not sulfate, making this microbe a non-traditional SRB, undetectable by culture media bottle methods Sulfide production poses both a souring and corrosion-based risk
Acid producing bacteria	Many bacteria form different organic acids during their metabolism, these acids can lead to corrosion of metal surfaces
Sulfur Cycling	A broad spectrum qPCR target evaluating the genetic capacity for microbial conversion of sulfur related compounds Supplementary to the total SRB qPCR primer set, the presence of “sulfur cycling” genes indicates a potential for microbial souring and/or MIC
Sulfur Oxidizing Bacteria	A qPCR primer targeting the oxidation of sulfur-related compounds (sulfide, sulfur, thiosulfate) to sulfate. Often considered a beneficial group of microbes as they function to remove sulfide (H2S) from a system, and are stimulated (used) in nitrate injection strategies for souring control. Recent research has indicated select SOB species can cause MIC by oxidizing sulfide to sulfuric acid (H2SO4).
Nitrate reducing bacteria	Nitrate reducing bacteria (NRB) gain energy for growth by reducing nitrate to nitrite Nitrate reduction is energetically favourable – NRB can outcompete SRB for growth on the same organics Nitrite is itself corrosive, but is also a potent inhibitor of SRB
Slime producing bacteria	Many microbes prefer to live in a sessile community known as a biofilm Biofilms are held together by a viscous slime or “extracellular matrix” Some microbes produce particularly large amounts of slime when growing as a biofilm, and therefore pose a proportionately greater risk to biofouling or clogging events
Souring	Oilfield souring is a phenomenon whereby oil or gas reservoirs are made “sour” by the presence of hydrogen sulfide, H2S. The sulfide source can be non-biogenic (sulfur containing deposits in the reservoir), but is often a result of sulfide producing bacteria (biogenic sulfide).
16S	16S is an rRNA gene found universally in all microbes (it encodes for highly important protein building machinery) that is analogous to a fingerprint – it can be used to identify the microbe(s) down to the species level. The 16S gene can be used in several molecular MIC tests
Archaea	A domain of microorganisms (microbes) very similar, yet distinct from bacteria.
ATP	Adenosine Triphosphate or ATP is the energy currency of cells. All cells (microbe or even human) use energy in the form of ATP to do work.
Bacteria	Single cell, microscopic organisms. Bacteria are found everywhere (capable of living under a very wide range of habitats including extreme environments).
Gene	A functional region/unit of DNA within an organism (microbe). Genes have codes to make proteins that provide a specific function to the microbe. Example, the dsrAB gene(s) codes for proteins that are used in sulfate reduction by SRB.
Metagenomics	Sequencing all of the 16S genes (reading all of the fingerprints) in a sample gives a list of all the microbes present, along with relative abundance percentages (semi-quantitative assay).
MIC	Microbiologically Influenced Corrosion (MIC) describes the corrosive damage to surfaces caused by microbes, including bacteria and archaea.
Microbe	A unifying term used to describe bacteria and archaea (microscopic, unicellular organisms).
MMM	Molecular Microbiological Methods (MMM) are culture-independent, genetic-based assays for MIC diagnostics.
qPCR	Quantitative Polymerase Chain Reaction (qPCR) is a molecular microbiological method (MMM) that functions by counting/enumerating instances of a gene of interest in a given sample. For example, by counting the number of 16S genes in a sample, one can quantify the total number of microbes.
Sequencing	see metagenomics