Natural transformation of adsorbed DNA and its role in the transfer of antimicrobial resistance

Antibiotic resistance is a major and increasing public health problem. I seek a better understanding of the agricultural and environmental side of this problem. What are the impacts of our widespread use of antibiotics in animal production? My past work on this topic has included measurements of antibiotics and antibiotic resistance on conventional and organic swine farms and lab reactor studies looking at the effects of antibiotics in a controlled environment.

Here I approached the question from a more fundamental perspective, looking at what controls horizontal gene transfer, and in particular the transfer of free DNA (natural transformation), in the soil environment. We have investigated how conditions such as solution chemistry and the presence of natural organic matter (NOM) affect DNA binding to mineral surfaces and its availability for natural transformation of the soil bacterium Azotobacter vinelandii.  We also investigated the role of motility in transport and natural transformation of A. vinelandii and integrated our experimental results with mathematical models of gene transfer.


Funding: USDA CSREES Agriculture and Food Research Initiative Water and Watersheds and NSF Hydrologic Sciences

Collaborators: Helen Nguyen (Illinois), Tim Ginn (UC Davis), Arash Massoudieh (Catholic University of America)

Students: Heather Goetsch & Nanxi Lu

Related publications:

Lu, N., A. Massoudieh, X. Liang, D. Hu, T. Kamai, T. R. Ginn, J. L. Zilles, T. H. Nguyen. 2015. Swimming motility reduces Azotobacter vinelandii deposition to silica surfaces. J Environ. Qual. 44(5):1366-1375 DOI:    10.2134/jeq2015.03.0141

Lu, N., A. Massoudieh, X. Liang, T. Kamai, J. L Zilles, T. H. Nguyen, T. R. Ginn. 2015. A kinetic model of gene transfer via natural transformation for Azotobacter vinelandii. Environmental Science: Water Research & Technology 1:363-374 DOI: 10.1039/C5EW00023H

Lu, N., T. Bevard, A. Massoudieh, C. Zhang, A. C. Dohnalkova, J. L. Zilles, T. H. Nguyen. 2013. Flagella-mediated differences in deposition dynamics for Azotobacter vinelandii in porous media. Environ. Sci. Technol. 47(10):5162–5170.

Lu, N., S. E. Mylon, R. Kong, R. Bhargava, J. L. Zilles, T. H. Nguyen. 2012. Interactions between dissolved natural organic matter and adsorbed DNA and their effect on natural transformation of Azotobacter vinelandii. Sci. Total Environ. 426:430-435.

Goetsch, H. E., S. E. Mylon, S. Butler, J. L. Zilles, and T. H. Nguyen. 2012. Adsorption of oxytetracycline to soil and its effects on natural transformation and growth inhibition of Azotobacter vinelandii. Environ. Toxicol. Chem.  2012 Jul 21. doi: 10.1002/etc.1945. [Epub ahead of print]

Lu, N., J. L. Zilles, and T. H. Nguyen. 2010. Adsorption of extracellular chromosomal DNA and its effects on natural transformation of Azotobacter vinelandii. Appl. Environ. Microbiol. 76(13):4179-84. free full text through PubMed