Effect of genome size andrrn gene copy numbers of PCR amplification products of 16S rRNA genes from mixed bacterial species

Results and conclusion As determined by image analysis of SYBR green-stained amplification products the experimentally determined ratio corresponded well with the expected ratio calculated from the number ofrrn genes per equimolar amount of DNA in mixtures containing DNA ofEscherichia coli and Thermus thermophilus and DNA ofPseudomonas aeruginosa and T. thermophilus. The values for the pairBacillus subtilis and T. thermophilus showed higher deviation from the predicted value. The dependence of the amount of 16S rDNA amplification products on these two parameters makes it impossible to quantify the number of species present in 16S rDNA clone library of an environmental sample, as long as these two parameters are unknown for these species.