Most common methods used for the detection of MIC
The study of MIC has become very prominent over the last years, and that is the main reason why new techniques are developed constantly in order to understand better how MIC works. However, many of the most innovative techniques are not affordable and require advanced equipment and trained personnel to interpret results. Techniques like XRD (X-ray diffraction), atomic force microscopy, confocal laser scanning microscopy, FISH (Fluorescence in situ hybridization), among others, have become major tools in understanding and learning more about biofilms, their structure and composition. From an academic point of view, these methods are promising and very informative. Sadly, for the fast-paced oil and gas industry most of these techniques won’t even be considered accessible.
Nowadays, there are three main techniques that are used almost everywhere and provide enough information to operators and technicians in order to assess the potential damage caused by corrosive microorganisms.
- Culture-based methods. These methods use liquid or solid bacterial media to calculate an approximated concentration of microbial cells present in a given volume. It is very popular with APB and SRB since these are the most common kinds found in MIC, and it involves using a tenfold serial dilution method of a sample in order to determine the MPN (most probable number). Culture-based methods are still the most common used worldwide due to its low cost and simplicity. They don’t require any special equipment more than an incubator, but it could take up to two weeks to obtain positive results. Most bacterial growth media tend to be specific to a certain kind of bacteria; however, false positives and contaminants can be present, so it is very important to learn how to interpret a positive culture. Media Available.
- Enzymatic assays. Most of these methods use ATP (adenosine triphosphate) as a target molecule that approximates the concentration of bacteria found in a sample. ATP is the “energy” molecule of all living organisms and it is responsible for pretty much all biochemical processes inside the cells. These methods are easy to follow and can be done in either a laboratory or on the field; however, they present a few limitations like not being able to differentiate among kinds of bacteria, and being susceptible to interference by physical aspects and chemical particles like oil, sand, and even salts. ATP-based tests are a very quick form of knowing whether there is a potential harmful number of bacteria in a system or not. ATP testing available
- Genetic-based methods. Nowadays there is a significant number of companies that provide these services. One of the most used ones is qPCR where specific DNA primers are used to target specific genes that are characteristics for certain groups of bacteria. Next generation sequencing (NGS) is another method that targets populations of microorganism as a whole and provides a complete phylogenetic profile about the dynamics in a given microbial community. All these methods continue to adapt and improve constantly providing more information about bacterial responsible for MIC. However, these services are still expensive for small companies and require trained personnel for running the tests and interpreting the respective results.
One method does not replace another; all these techniques mentioned above complement each other since they use different approaches to obtain information about a microbial population responsible for MIC in a particular environment.