General mcrA primers for quantifying methanogens using a SYBR Green-based assay. ABCD1NameDirectionSequenceCitation2mlas_modFwdGGY GGT GTM GGD TTC ACM CAR TAAngel et al., 20113mcrA_revRevCGT TCA TBG CGT AGT TVG GRT AGTSteinberg and Regan, 2008