For DNA amplification and quantitative PCR (qPCR) analysis, Each qPCR assay requires ~ 10 to 50 ng of genomic DNA, thus 1 µg of genomic DNA from the sample is adequate for repeated analysis. With an average bacterial genome size of 2 x10 6bp, about 5 x 10 8 bacteria will yield 1 µg of genomic DNA. The size of the sample required to yield 5 x 10 8 bacteria varies depending on the source:

• Less than or equal (≤) 100 ml of sewage /wastewater
• 10 liters or more of marine or fresh water sample .