Top Lab: Randal Fox

My research in laboratory of Dr. Eva Top has been divided into two areas:

 Evolution of unfavorable plasmid-host association

 The plasmid pB10 is a broad-host-range antibiotic resistance plasmid with the ability to transfer to and replicate in most Gram-negative bacteria. It has been shown that pB10 has been stably maintained in several species in the absence of antibiotics. My work was to view whether there are some Gram-negative species that are not well adapted to pB10, or in other words, species in which pB10 is less stable or has a high cost. I isolated transconjugants from various habitats and determined that plasmid pB10 showed a low stability and a high cost in a P. putida strain, designated H2.  Strain H2 with pB10 was evolved in medium with antibiotics for 1000 generations. After 1,000 generations, the stability of the evolved plasmids in the ancestral host had increased and the metabolic burden decreased.  A manuscript (Holger Heuer, Randal Fox, and Eva Top) is in press in FEMS Microbiol. Ecol.

 Invasion of a plasmid free population of E. coli by plasmid pB10.

 Recent genomic data indicate that horizontal gene transfer is an essential mechanism in the adaptive evolution of bacteria.  This is also very evident in the emergence and rapid spread of antibiotic resistance genes. We are investigating how spatial structure is a key determinant in the spread and persistence of antibiotic resistance plasmids in bacterial populations, and how stochastic cellular automata models can accurately predict the resulting behavior.  My goal is to examine the effects of spatial structure on the persistence and spread of resistance plasmids on agar plates.  I am studying the effects of nutrient concentration on the ability of pB10 to spread through a spatially structured population of plasmid free cells.  Results show that this is possible under certain environmental conditions in at least two species.

I am working towards a Bachelor’s degree and Master’s degree in Microbiology, Molecular Biology & Biochemistry through the Seamless Master’s Program.  Anticipated graduation date:  May 2007.

Peer-Reviewed

Holger Heuer, Randal E. Fox, Eva M. Top. Frequent conjugative transfer accelerates adaptation of a broad-host-range plasmid to an unfavourable Pseudomonas putida host.  FEMS Microbiol. Ecol.  (In press)

Stephen M. Krone, Ruinan Lu, Randal E. Fox, and Eva M. Top.  Modeling the Spatial Dynamics of Plasmid Transfer and Persistence. (In Prep.)

Abstracts

Top E.M., L. De Gelder, H. Heuer, R. Fox, R. Ganta, L.J. Forney, J. Ponciano, Z. Abdo, P. Joyce, R. Lu, S. Krone. 2005.  Ecology and evolution of broad-host-range plasmids: time for new quantitative approaches.  Plasmid 53: 57 (Presented at the 2004 Plasmid Biology Meeting in Kanoni, Greece)

Presentations

Poster

Randal Fox, Holger Heuer, Eva M. Top. IncP-1 plasmid pB10 is unstable and costly in P. putida H2.  2003 Northwest Branch Meeting of the American Society of Microbiology in Vancouver, Canada

Randal Fox, Holger Heuer, Eva M. Top. IncP-1 plasmid pB10 is unstable and costly in P. putida H2.  2003 COBRE External Advisory Committee Meeting in Moscow, Idaho.

Randal Fox, Holger Heuer, Eva M. Top.  Rapid coevolution of a broad-host-range antibiotic resistance plasmid with its bacterial host.  2004 Idaho BRIN/INBRE Annual Meeting in Pocatello, Idaho.

Randal Fox, Holger Heuer, Eva M. Top.  Rapid coevolution of a broad-host-range antibiotic resistance plasmid with its bacterial host.  2004 COBRE External Advisory Committee Meeting in Moscow, Idaho.

Randal E. Fox, Eva M. Top. Invasion of a plasmid free population of E. coli by plasmid pB10.  2006 Northwest Branch Meeting of the American Society of Microbiology in Seattle, WA.

Eva M. Top, Ruinan Lu, Randal Fox, and Stephen M. Krone.  Modeling the Spatial Dynamics of Plasmid Transfer and Persistence.  2006 Northwest Branch Meeting of the American Society of Microbiology in Seattle, WA.

Randal E. Fox and Eva M. Top. Invasion of a plasmid free population of E. coli by the IncP-1b plasmid pB10.  2006 Plasmid Biology Meeting in Lake Tahoe.