Horizontal Gene Transfer in Porous Media: A Real Time Microscopic Investigation
EMSL Project ID
44692
Abstract
Horizontal gene transfer is widespread among bacteria and is an important component of microbial evolution and trait dispersal. Specifically, gene transfer can create new metabolic capabilities, e.g., for degradation of new anthropogenic contaminants, and can facilitate the dissemination of existing capabilities, such as antimicrobial resistance. Soil surfaces provide a natural reservoir for transferrable DNA because sorbed DNA avoids aqueous phase enzymatic degradation and can transform soil bacteria. Cell motility can exert primary control on the frequency with which cells associate with surfaces, and therefore is likely to affect the frequency of interaction between the cells and adsorbed DNA. Thus the work proposed here investigates the relationships among cell motility, cell attachment and transport, and gene transfer by extracellular DNA. Our goal is to identify controls on the kinetic rate of transformation of bacteria, as a resident-time dependent surface reaction. Transformation should involve truly surface-associated cells, so cells will transform only upon passage through secondary minima to reach primary minima attachment. Thus transformation kinetics of both motile and non-motile cells will depend on their residence-time on surfaces coated with extracellular DNA. In this context we will test the following two hypotheses: (1) The rates of gene transfer for non-motile bacteria depend primarily on the attachment efficiency to porous media surfaces, governed by biocolloid-surface interaction forces; (2) The rates of gene transfer for motile bacteria depend primarily on their swimming behavior. The ability of motile cells to swim allows them to approach surfaces independent of aqueous chemistry controls on biocolloid-surface interaction forces. Consequently motile cells will exhibit greater frequency of transformation in porous media than non-motile cells. These hypotheses will be tested through specific experimental and modeling objectives involving determination of attachment mechanisms in a radial stagnation point flow (RSPF) system, of residence time distributions and spatial distribution in a micromodel system, and of attachment-detachment and gene transfer kinetics in batch and column systems. The experiments will involve both motile and non-motile bacterial strains and will use surfaces coated with extracellular DNA. Results will be used in the development and testing of models of bacterial transport and horizontal gene transfer in porous media.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2011-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
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