If you need clarification pls tell me but try to use that explanation: ......to convert copy numbers per microlitre (µL) to copy numbers per gram of dry soil, it is important to understand the key parameters involved: the copy number concentration of the extracted DNA solution, the total volume of that extract, and the dry weight of the soil sample used during DNA extraction.

The process begins by determining the copy number per microlitre of extracted DNA solution, typically obtained from quantitative PCR (qPCR) or another absolute quantification method. This value represents the number of target DNA molecules in one microlitre of the extracted sample. To find the total number of copies in the whole extract, multiply the number of copies per microlitre by the total volume of the extracted DNA solution. For example, if your quantification result is 5,000 copies per microlitre and the total extract volume is 200 microlitres, the total copy number in the extract would be 1,000,000 copies (calculated as 5,000 copies/µL multiplied by 200 µL).

Next, it is essential to determine the dry weight of the soil sample used for DNA extraction. This weight should be measured prior to the extraction process to ensure that the soil is completely dry to remove any moisture content which could otherwise affect the results. Let's assume that 0.5 grams of dry soil was used.

To convert the copy number to a per gram basis, divide the total copy number obtained from the extract by the dry weight of the soil. In our example, dividing 1,000,000 copies by 0.5 grams of soil gives 2,000,000 copies per gram of dry soil. This value provides a standardised measurement that reflects the abundance of target DNA in the soil sample, regardless of the initial volume or concentration of the extracted solution.

It is important to take into account any dilution steps taken during the preparation or quantification of the DNA extract. If the DNA extract has been diluted prior to quantification, this dilution must be taken into account in order to accurately determine the total copy number in the original extract. In addition, ensuring consistent units of measurement - such as grams for soil weight and microlitres or millilitres for volume - will help avoid conversion errors and maintain accuracy.

Thank you so much for this Phil Käding ! This is the only answer I had obtained despite a lot of googling.

I do have a follow up question when it comes to the dilution. Do you mind guiding me with the calculation if the samples were diluted (let say 1:10) prior to quantification?

When you dilute a sample, you are essentially reducing the concentration of DNA in the extract by a specific factor. For instance, a 1:10 dilution means that one part of the sample is mixed with nine parts of diluent (e.g., water or buffer). Therefore, the DNA concentration in the diluted sample is ten times lower than in the original extract.

To find the actual copy number concentration in the original, undiluted extract, you must account for the dilution factor in your calculation. Assume that after a 1:10 dilution, you measure 5,000 copies per microlitre (copies/µL) using quantitative PCR (qPCR).

To determine the original concentration, multiply the measured copy number by the dilution factor:

Original concentration = Measured concentration × Dilution factor

Substitute the values:

Original concentration = 5,000 copies/µL × 10 = 50,000 copies/µL

did you mean it that way? or do you need more steps?