Jm. Calvo et Rg. Matthews, THE LEUCINE-RESPONSIVE REGULATORY PROTEIN, A GLOBAL REGULATOR OF METABOLISM IN ESCHERICHIA-COLI, Microbiological reviews, 58(3), 1994, pp. 466-490
Natural genetic transformation is the active uptake of free DNA by bac
terial cells and the heritable incorporation of its genetic informatio
n. Since the famous discovery of transformation in Streptococcus pneum
oniae by Griffith in 1928 and the demonstration of DNA as the transfor
ming principle by Avery and coworkers in 1944, cellular processes invo
lved in transformation have been studied extensively by in vitro exper
imentation with a few transformable species. Only more recently has it
been considered that transformation may be a powerful mechanism of ho
rizontal gene transfer in natural bacterial populations. In this revie
w the current understanding of the biology of transformation is summar
ized to provide the platform on which aspects of bacterial transformat
ion in water soil, and sediments and the habitat of pathogens are disc
ussed. Direct and indirect evidence for gene transfer routes by transf
ormation within species and between different species will be presente
d, along with data suggesting that plasmids as well as chromosomal DNA
are subject to genetic exchange via transformation. Experiments explo
ring the prerequisites for transformation in the environment, includin
g the production and persistence of free DNA and factors important for
the uptake of DNA by cells, will be compiled, as well as possible nat
ural barriers to transformation. The efficiency of gene transfer by tr
ansformation in bacterial habitats is possibly genetically adjusted to
submaximal levels. The fact that natural transformation has been dete
cted among bacteria from all trophic and taxonomic groups including ar
chaebacteria suggests that transformability evolved early in phylogeny
. Probable functions of DNA uptake other than gene acquisition will be
discussed. The body of information presently available suggests that
transformation has a great impact on bacterial population dynamics as
well as on bacterial evolution and speciation.