2009-04-19

comB7, comB8, comB9, comB10

TfoX

http://jb.asm.org/cgi/content/abstract/191/3/713 "The putative outer membrane channel protein (HofQ), transformation pseudopilus component (PpdD), and transmembrane pore (YcaI) are not required for plasmid transformation." .. "Our data together, with previous reports that HofQ is required for the use of dsDNA as a carbon source, suggest the existence of two routes for DNA entry, at least across the outer membrane of E. coli."

http://www.pnas.org/content/92/8/3616.abstract "Collectively, our results suggest that TfoX may play a key role in the development of genetic competence by regulating the expression of late competence-specific genes."

A New Transformation-Deficient Mutant of Haemophilus influenzae Rd with Normal DNA Uptake

http://jb.asm.org/cgi/content/abstract/180/3/746

"Haemophilus influenzae Rd is a gram-negative natural transformer. A mutant strain, RJ248, that has normal DNA uptake and translocation but whose transformation frequency is 300 times lower than that of wild-type H. influenzae and whose phage recombination is 8 times lower was isolated. The affected gene, comM, is induced during competence development in wild-type H. influenzae but not in RJ248."

requirement: comM

organism: Haemophilus influenzae Rd RJ248

A unique nine-gene comY operon in Streptococcus mutans

http://mic.sgmjournals.org/cgi/content/abstract/151/1/157

"Many Gram-positive and Gram-negative bacteria possess natural competence mechanisms for DNA capture and internalization. In Bacillus subtilis, natural competence is absolutely dependent upon the presence of a seven-gene operon known as the comG operon (comGA–G). In species of Streptococcus, this function has been described for a four-gene operon (comYA–D in Streptococcus gordonii and cglA–D in Streptococcus pneumoniae). In this study, a nine-orf operon (named comYA–I) required for natural competence in Streptococcus mutans was identified and characterized."

see the paper "Internalizing DNA" for a list of genes required for natural competence in B. subtilis and a deescription of what they are and how they were found (or guessed).

"Natural genetic competence is a genetically-encoded physiological state where the bacteria becomes capable of taking up naked/free/extracellular DNA (Chen and Dubnau, 2004; Dubnau, 1999; Lorenz and Wackernagel, 1994). Natural competence is a transient state in most naturally transformable bacteria (Lorenz and Wackernagel, 1994) and results from the growth of a bacterial culture under defined growth conditions, or it is, as in Neisseria gonorrhoea (Lorenz and Wackernagel, 1994; Thomas and Nielsen, 2005), constitutively expressed under all growth conditions (Dubnau, 1991) The evolution of the DNA uptake systems in bacteria can be accounted for by the use of incoming DNA as nutrition (Redfield, 2001), as templates for repair of DNA, or for genetic diversity by acquisition of potential useful genetic information such as antibiotic resistance (Chen and Dubnau, 2004). Competence has been found to involve approximately 20 to 50 proteins and approximately 1% of the validly described bacteria species have been found to be naturally transformable (Thomas and Nielsen, 2005)."

Competence has been found to involve approximately 20 to 50 proteins and approximately 1% of the validly described bacteria species have been found to be naturally transformable (Thomas and Nielsen, 2005).

Neisseria gonorrhoea (Lorenz and Wackernagel, 1994; Thomas and Nielsen, 2005), constitutively expressed under all growth conditions (Dubnau, 1991)

Thomas CM and Nielsen KM (2005) Mechanisms of, and barriers to, horizontal gene transfer between bacteria. Nature Reviews Microbiology 3:711-721.

Sixteen competence genes has been identified in Acinetobacter baylyi; comA, comEA, dprA, comP, comE, comF, comB, comC, pilD, pilC, pilB, comQ, comL, comM, comN, and comO (see figure 1) (Averhoff and Graf, 2008).

Averhoff B and Graf I (2008) The natural transformation system of Acinetobacter baylyi ADP1: A unique DNA transport machinery, in Acinetobacter Molecular Biology pp 120-139, Caister Academic Press, Norfolk, UK.

pg 13 Acquisition of foreign DNA by natural transformation in Acinetobacter baylyi - introgression process.pdf

For homologous recombination to occur the incoming DNA must contain regions of minimum 25 to 200 base pairs (bp) in length of similarity to the recipient genome (Thomas and Nielsen, 2005).

while most other species bind and take up DNA independently of its sequence (Lorenz and Wackernagel, 1994).