Genetic competence refers to the ability of some bacteria to undergo transformation — to take up exogenous DNA and incorporate it stably into their own genome.
Naturally transformable organisms express specialized proteins that function in DNA uptake and processing. These proteins are usually conserved among the competent bacteria, both Gram-positive and Gram-negative.
Among the proteins that are involved in DNA uptake, a subset is related to components of the type IV pilus and type II secretion systems. In piliated Gram-negative organisms, these proteins are involved in both pilus formation and DNA uptake, leading to a correlation between these two phenotypes.
The function of this group of proteins is to bring DNA from the surface, across the outer membrane, peptidoglycan layer and periplasmic space (in Gram-negatives), or across the cell wall (in Gram-positives), to the cytoplasmic membrane.
By contrast, Helicobacter pylori uses proteins that are related to components of the type IV secretion and conjugation systems to bring DNA to the cytoplasmic membrane.
A translocation complex mediates the transport of DNA across the cytoplasmic membrane. The proteins in this complex are: a DNA receptor, a polytopic membrane protein that can form a channel and an ATP-binding protein. These components show characteristics of elements from ABC transporter systems.
Naturally competent bacteria are able to take up exogenous DNA and undergo genetic transformation. The transport of DNA from the extracellular milieu into the cytoplasm is a complex process, and requires proteins that are related to those involved in the assembly of type IV pili and type II secretion systems, as well as a DNA translocase complex at the cytoplasmic membrane. Here, we will review the current knowledge of DNA transport during transformation.
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We thank members of our laboratory for helpful discussions and L. Mindich and B. Mulder for comments on the manuscript. We apologize to investigators whose work was not mentioned due to space constraints. The work cited from our lab was supported by NIH grants.
The authors declare no competing financial interests.
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Chen, I., Dubnau, D. DNA uptake during bacterial transformation. Nat Rev Microbiol 2, 241–249 (2004). https://doi.org/10.1038/nrmicro844
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