( mple ranged from 0.07 to 0.3...)Monitoring Microbial Populations Using Real-Time qPCR on the MJ Research Opticon 2 System

The graph in Figure 1 plots relative quantification of the amoA gene for the 16 soil samples and indicates the environmental treatments for the corresponding soil plots. For these representative samples, relative levels of the amoA gene ranged from as low as 0.167 (sample 16) to as high as 5.24 (sample 9), a 32-fold difference.

Discussion
In this study, DNA was successfully extracted from soil samples and the relative amounts of amoA were determined. The real-time qPCR procedure was used to reliably quantify amoA across a 32-fold range in the 16 representative samples, well within the dynamic range of detection of the DNA Engine Opticon 2 system.¹⁰ The 32-fold range of amoA levels in the samples suggests a dramatic impact of different environmental stimuli on the population size of AOB. A complete description of the experimental design and statistical analysis of the larger sample set collected from the different environmental treatment groups can be found in Horz et al. (2004).⁷

Advantages of Real-time PCR to Analyze Population Size
Real-time qPCR provides several advantages for quantification of gene levels. The sensitivity and dynamic range of detection for this method enables analysis of both low- and high- abundance targets within a sample set.^{10, 11} The specificity and high throughput of the assay allows gene sequences in DNA from small biomass samples to be detected efficiently in a large number of samples. Primer sets for other specific functions or for individual taxons should allow the effects of environmental changes
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