The higher taxonomic groups within prokaryotes are presently distinguished mainly on the basis of their branching in phylogenetic trees. In most cases, no molecular, biochemical or physiological characteristics are known that are uniquely shared by species from these groups. Analyses of genome sequences are leading to discovery of novel molecular characteristics that are specific for different groups of bacteria and archaea and provide more precise means for identifying and circumscribing these groups of microbes in clear molecular terms and for understanding their evolution (Xu, 2010).

References:
Xu, J. (2010) Microbial Population Genetics. Caister Academic Press, Norfolk, UK.

Labels: Microbial evolution, Phylogenetic trees