3.2 DNA isolation and library preparation

As in phenotypic surveillance, you’ll begin wet-laboratory work for WGS by culturing your samples. However, the next steps will differ somewhat from the usual microbiology laboratory work. For WGS, laboratory technicians must conduct DNA extraction, where cells from a pure culture are broken to isolate the DNA, and proteins and cell debris are removed.

You should also measure the extracted DNA (quantitation) to make sure that you have the specific volume and amount of DNA needed for the library preparation step that follows.

The next step in preparing for sequencing in the laboratory is called library preparation. This step includes modifying the ends of the DNA that you’ve extracted to make sure they are recognised and read by the sequencing machine. Additional steps may also be included, depending on the sequence technology being used (CDC, 2024).