If the "DNA analysis" isn't entirely invented then my guess is that they have analysed the DNA of a mixture of microorganisms that happened to be present on the specimens.
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To proceed with the NGS run a library of the fragments to sequence has to be prepared first. This library preparation method was performed by CEN4GEN using a specialized protocol
proprietary of CEN4GEN labs and reagents kits based on a commercial kit called Kapa Hyper Prep that were optimal to recover fragmented DNA for ancient samples. The results of the library construction methods were successfully performed for the 3 MDA amplified samples as shown below.
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