Answer:
DNA is the genetic material of almost all the prokaryotes and the DNA sequence of the same species is almost same but the DNA sequence of different species are not same. Metagenomics is a DNA sequence approach which is used by scientist to identify the new species of prokaryotes.
An organism is said to be of new species if it has a difference in the DNA sequence from the DNA sequence of members of other species that are known today.
So DNA testing helps in identifying the new prokaryote species by identifying the new DNA sequence in that prokaryote. Scientists also use rRNA sequence to find the evolutionary relationship between species.