| Five parameters can be used to genetically define a species: (i) relatedness
at conditions optimal for DNA re-association, (ii) relatedness at conditions
less than optimal for DNA re-association (at which only highly complementary
sequences can re-associate), (iii) divergence in related nucleotide sequences,
(iv) genome size, and (v) G+C content of DNA. The first three parameters are
exclusive; e.g., if strains of a given species are 90% inter-related, they cannot
be equally related to any other species, or if their related sequences show 2%
divergence, they must exhibit a greater level of divergence to all other species.
The last two parameters are not exclusive [92]. |
