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. 2006 Jun;188(11):3902-10.
doi: 10.1128/JB.01974-05.

V体育官网入口 - Escherichia coli competence gene homologs are essential for competitive fitness and the use of DNA as a nutrient

Vyacheslav Palchevskiy  1 , Steven E Finkel
Affiliations

"VSports最新版本" Escherichia coli competence gene homologs are essential for competitive fitness and the use of DNA as a nutrient

Vyacheslav Palchevskiy et al. J Bacteriol. 2006 Jun.

Abstract

Natural genetic competence is the ability of cells to take up extracellular DNA and is an important mechanism for horizontal gene transfer. Another potential benefit of natural competence is that exogenous DNA can serve as a nutrient source for starving bacteria because the ability to "eat" DNA is necessary for competitive survival in environments containing limited nutrients. We show here that eight Escherichia coli genes, identified as homologs of com genes in Haemophilus influenzae and Neisseria gonorrhoeae, are necessary for the use of extracellular DNA as the sole source of carbon and energy VSports手机版. These genes also confer a competitive advantage to E. coli during long-term stationary-phase incubation. We also show that homologs of these genes are found throughout the proteobacteria, suggesting that the use of DNA as a nutrient may be a widespread phenomenon. .

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Figures

FIG. 1.
FIG. 1.
Long-term survival and competition patterns of com gene mutants. (A) Superimposition of nine growth curves of wild-type and mutant strains grown separately as monocultures. (B) Superimposition of competition assays of cells grown in coculture. Each mutant strain was competed against the wild type. A single representative wild-type strain is shown. Mutant strains (solid lines) are grouped by their competition phenotype and indicated by symbols as follows: yrfD, squares; hofQ, yhiR, yrfC, and yrfB, triangles; and yhgI, yhgH, and yrfA, circles. Asterisks indicate no detectable cells. Representative data are shown.
FIG. 2.
FIG. 2.
Relative fitness of com mutants. (A) Schematic representation of the construct used for multiplex experiments; the asterisk indicates that the position of the upstream “check” primer varies for each gene mutated; (B) The eight knockout mutants were coinoculated in a single LB culture. The culture was sampled periodically, and PCR was performed to identify bands corresponding to each mutant. The presence of each product indicates the survival of a particular mutant strain. The bands in the right panel show the band sizes for each mutant. Representative data are shown.
FIG. 3.
FIG. 3.
Average growth yields of wild-type (WT) or com mutant cells in minimal medium supplemented with 0.1% ultrapure sonicated salmon sperm DNA as the sole source of carbon and energy. Growth yields (indicated above each bar) were determined by dividing the number of cells after 24 h of incubation by the number of cells at inoculation.
FIG. 4.
FIG. 4.
Catabolism of nucleobases, nucleosides, and dNMPs by wild-type (□) and com mutant (○) strains. Long-term survival data are shown for the wild-type and eight com mutant strains grown in adenine (A), adenosine (B), or dAMP (C) as the sole source of carbon and energy. Representative data are shown.
FIG. 5.
FIG. 5.
Model of DNA uptake and catabolism in E. coli. The outer membrane, inner membrane, and cell wall (dashed line) are depicted, defining the borders of the extracellular space, periplasm, and cytoplasm. Ovals represent putative cell surface dsDNA binding and transport complexes. Rectangles represent putative inner membrane transport and processing complexes. The “Pac-Man” represents cytoplasmic ssDNA processing enzymes, including nucleases. Small dots represent degraded DNA or nucleotides. (Step 1) Extracellular dsDNA is bound by a surface receptor on the outer membrane, and dsDNA is transported across the outer membrane to the periplasm, probably through a porin encoded by hofQ; (step 2) dsDNA is processed to ssDNA, in the periplasm or possibly during transit across the inner membrane; (step 3) nucleotides from the degraded strand are released into the periplasm; and (step 4) ssDNA is processed to nucleotides in the cytoplasm which are further metabolized.
FIG. 6.
FIG. 6.
com gene homologs. The presence (+) or absence (−) of each of the eight com gene homologs is indicated to the right of a phylogenetic tree based on small-subunit rRNA. Genera or groups that have members with or without homologs are indicated by “+” or “−”, respectively. Distances are not drawn to scale.
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References

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