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Mobility of extracellular DNA within gonococcal colonies
Niklas Bender1, Marc Hennes1, Berenike Maier1,2
1Institute for Biological Physics, University of Cologne, Zülpicherstr. 47a, 50647, Köln, Germany.
Biofilm
|June 1, 2022
Summary
Bacterial transformation relies on extracellular DNA (eDNA) mobility. Neisseria gonorrhoeae colonies trap longer DNA fragments and those with DNA uptake sequences (DUS), limiting transformation to colony edges.
Area of Science:
- Microbiology
- Bacterial genetics
- Molecular biology
Background:
- Bacterial transformation is a key mechanism for genetic exchange, involving the uptake of extracellular DNA (eDNA).
- Bacterial colony structure can influence eDNA diffusion and accessibility for transformation, impacting genetic diversity.
Purpose of the Study:
- To investigate the mobility of extracellular DNA within Neisseria gonorrhoeae colonies.
- To correlate DNA mobility with transformation efficiency in N. gonorrhoeae colonies.
- To understand the role of DNA length and the DNA uptake sequence (DUS) in modulating DNA mobility and transformation.
Main Methods:
- Characterization of fluorescent DNA fragment penetration dynamics into N. gonorrhoeae colonies over hours.
- Analysis of DNA concentration gradients within colonies based on DNA length and the presence of DUS.
- Assessment of transformation efficiency in relation to DNA diffusion patterns within young colonies.
Main Results:
- Short DNA fragments (300 bp) diffused freely within N. gonorrhoeae colonies.
- Longer DNA fragments (>3 kbp) exhibited hindered diffusion, forming concentration gradients from colony edge to center.
- The DNA uptake sequence (DUS) significantly reduced DNA mobility, trapping DNA at the colony periphery, and transformation was restricted to the colony edge.
Conclusions:
- DNA mobility in N. gonorrhoeae colonies is dependent on DNA length and specific interactions mediated by the DUS.
- The DUS binding to type 4 pili restricts gonococcal DNA mobility, limiting transformation to specific colony regions.
- N. gonorrhoeae colonies can act as reservoirs for eDNA, accumulating DNA and potentially influencing horizontal gene transfer.
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