Domains of Life: Archea and Bacteria
The identification of prokaryotic organisms is complicated by the fact that their genomes have been heavily impacted by the horizontal transfers of DNA (Koonin et al. 2001). For example, complete genome analysis on three strains of E. coli revealed that they shared just 39.3% of their protein-coding genes (Welch et al. 2003). Despite such genomic fluidity, species units do exist in these taxonomic groups. Moreover, by focusing analysis on core genomic regions, an effective DNA-based identification system can be created without a massive survey of genic diversity. It is, for example, now accepted that the sequence analysis of just 6-9 genes provides enough information to enable separation of closely allied microbes (Unwin and Maiden 2003).
References
- Koonin, E. V., K. S. Msakarova and L. Arvind. 2001. Horizontal gene transfer in prokaryotes: quantification and classification. Annu. Rev. Microbiol. 55: 709-742.
- Unwin, R. and M. C. J. Maiden. 2003. Multi-locus sequence typing: a tool for global epidemiology. Trends Microbiol. 11: 479-487.
- Welch, R. A. and 18 coauthors. 2003. Extensive mosaic structure revealed by the complete genomic sequence of uropathogenic Escherichia coli. Proc. Natl. Acad. Sci. USA 99: 17020-17024.