Lineage: Bacteria[4017]; Proteobacteria[1676]; Gammaproteobacteria[748]; Enterobacteriales[160]; Enterobacteriaceae[160]; Escherichia[7]; Escherichia coli[1]Escherichia coli. This organism was named for its discoverer, Theodore Escherich, and is one of the premier model organisms used in the study of bacterial genetics, physiology, and biochemistry. This enteric organism is typically present in the lower intestine of humans, where it is the dominant facultative anaerobe present, but it is only one minor constituent of the complete intestinal microflora. E. coli, is capable of causing various diseases in its host, especially when they acquire virulence traits. Strains of E. coli can cause urinary tract infections, neonatal meningitis, and many different intestinal diseases, usually by attaching to the host cell and introducing toxins that disrupt normal cellular processes. Virulence proteins may be encoded on extrachromosomal plasmids or within bacteriophages and distinct DNA segments termed pathogenicity islands (PAIs). PAIs are likely to have been transferred horizontally and may even have integrated into the chromosome through bacteriophage or plasmid integration or transposition. [Source: NCBI Genome ]