Natural Competence - Regulation of Competence

Regulation of Competence

In laboratory cultures natural competence is usually tightly regulated and often triggered by nutritional shortages or adverse conditions. However the specific inducing signals and regulatory machinery are much more variable than the uptake machinery, and little is known about the regulation of competence in the natural environments of these bacteria. Transcription factors have been discovered which regulate competence; an example is sxy (also known as tfoX) which has been found to be regulated in turn by a 5' non-coding RNA element. In bacteria capable of forming spores, conditions inducing sporulation often overlap with those inducing competence. Thus cultures or colonies containing sporulating cells often also contain competent cells. Recent research by Süel et al. has identified an excitable core module of genes which can explain entry into and exit from competence when cellular noise is taken into account.

Most competent bacteria are thought to take up all DNA molecules with roughly equal efficiencies, but bacteria in the families Neisseriaceae and Pasteurellaceae preferentially take up DNA fragments containing short DNA sequences, termed DNA uptake sequence (DUS and USS respectively), that are very frequent in their own genomes. Neisserial genomes contain thousands of copies of the preferred sequence GCCGTCTGAA, and Pasteurellacean genomes contain either AAGTGCGGT or ACAAGCGGT.