There is an increasing need by the oil industry and downstream related industries to monitor microbial communities in ‘real time’ in order to address specific issues such as oil field souring, microbiologically influenced corrosion (MIC) and biofouling. Molecular Microbiology Methods (MMM) can be applied to oil fields (and other oil-related industries) to analyze and quantify the in-situ microbial communities and their activities in response to changing environmental conditions. Such information will help oil companies to employ more directed, cost-effective strategies to prevent the major problems associated with deleterious microbial activities, as well as to encourage beneficial microbes.