qPCR is used to evaluate biodegradation potential or activity in contaminated groundwater. qPCR is used to detect and quantify bacteria such as dehalococcoides mccartyi as well as vinyl chloride reductase functional genes essential to the biodegradation of chlorinated solvents including trichloroethene and tetrachloroethylene. qPCR is also commonly used to quantify functional genes involved in the biodegradation of benzene, toluene, ethylbenzene, and xylenes (BTEX) and evaluate monitored natural attenuation (MNA) or other remedial methods at impacted petroleum hydrocarbon sites. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR), which is based on the analysis of RNA rather than DNA, is used to quantify gene expression and identify biodegradation activity.