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Inhibition of bacterial conjugation by phage M13 and its protein g3p: quantitative analysis and model
Abraham Lin1, Jose Jimenez, Julien Derr
1FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts, United States of America.
Abstract:
Conjugation is the main mode of horizontal gene transfer that spreads antibiotic resistance among bacteria. Strategies for inhibiting conjugation may be useful for preserving the effectiveness of antibiotics and preventing the emergence of bacterial strains with multiple resistances. Filamentous bacteriophages were first observed to inhibit conjugation several decades ago. Here we investigate the mechanism of inhibition and find that the primary effect on conjugation is occlusion of the conjugative pilus by phage particles. This interaction is mediated primarily by phage coat protein g3p, and exogenous addition of the soluble fragment of g3p inhibited conjugation at low nanomolar concentrations. Our data are quantitatively consistent with a simple model in which association between the pili and phage particles or g3p prevents transmission of an F plasmid encoding tetracycline resistance. We also observe a decrease in the donor ability of infected cells, which is quantitatively consistent with a reduction in pili elaboration. Since many antibiotic-resistance factors confer susceptibility to phage infection through expression of conjugative pili (the receptor for filamentous phage), these results suggest that phage may be a source of soluble proteins that slow the spread of antibiotic resistance genes.
Insights
Bacteriophages, or phages, can inhibit bacterial conjugation, a key process in spreading antibiotic resistance. Soluble phage proteins effectively block this gene transfer, offering a novel strategy against resistant bacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Conjugation is a primary mechanism for the spread of antibiotic resistance genes among bacteria.
- Inhibiting conjugation is crucial for preserving antibiotic effectiveness and preventing multi-drug resistance.
- Filamentous bacteriophages have been previously observed to inhibit bacterial conjugation.
Purpose of the Study:
- To investigate the mechanism by which filamentous bacteriophages inhibit bacterial conjugation.
- To determine the role of phage particles and specific phage proteins in conjugation inhibition.
- To explore the potential of phage-derived proteins as therapeutic agents against antibiotic resistance.
Main Methods:
- Studying the interaction between filamentous phage particles and bacterial conjugative pili.
- Quantifying the effect of phage particles and soluble phage protein g3p on F plasmid transfer.
- Measuring the impact of phage infection on bacterial donor ability and pilus elaboration.
Main Results:
- Filamentous phage particles inhibit conjugation primarily by occluding the conjugative pilus.
- The phage coat protein g3p is the main mediator of this interaction.
- Exogenous soluble g3p inhibited conjugation at low nanomolar concentrations.
- Phage infection reduced bacterial donor ability, consistent with reduced pilus elaboration.
Conclusions:
- Filamentous bacteriophages, particularly their soluble g3p protein, can effectively inhibit bacterial conjugation.
- Phage particles and g3p physically block conjugative pili, preventing plasmid transmission.
- These findings suggest phage-derived proteins as a potential strategy to combat the spread of antibiotic resistance.
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