you mean primer for some reference genes (with constitutive expression)? You can try ITS genes (Internal Transcribed Spacer) region between ribosomal subunits.
Hi, I have used the primers EUB338 5' ACT CCT ACG GGA GGC AGC AG 3' and EUB518 5' ATT ACC GCG GCT GCT GG 3' listed in the following paper "Assessment of Soil Microbial Community Structure by Use of Taxon-Specific Quantitative PCR Assays" with great success in qPCR experiments.