|
| research | about me | publications | projects | contact | e-mail |
Overview of research
What factors regulate evolutionary diversity? Currently, I study the ecological and genetic factors that contribute to the origin and maintenance of antibiotic resistance diversity in bacterial biofilm communities.
Biofilms are bacterial communities that live at the interface of a surface and medium. Biofilms grow in diverse habitats, from the surface of rocks on the bottom of fresh water streams, to the surface of indwelling devices and medical implants, to the plaque on our teeth. Bacteria in biofilms are often highly tolerant to antibiotics, which makes treating biofilm associated infections difficult. Thus, there is interest in understanding why and how biofilms are resistant to antibiotics. I bring an evolutionary approach to the question, by testing whether antibiotic resistance evolves during the course of biofilm development.
|
 |
To date, I have found that the biofilm communities in the lab evolve high levels of variation in antibiotic sensitivity. Subsequently, I am trying to establish whether the biofilm environment selects for and maintains divergent phenotypes, or whether the variation is simply neutral. This work involves developing models involving stochastic and deterministic processes, and then using data from the lab to arbitrate between the models. This work is in collaboration with Luke Harmon, Paul Joyce, Jose Ponciano and Larry Forney.
I am also interested in mutation, the ultimate source of all genetic variation. It is unknown whether mutation rates are elevated in biofilm communities, and if so, whether variation in mutation rates is genetic (e.g., there are mutator alleles in the population) or context dependent (i.e., environmental, e.g., under biofilm conditions, mutation rates increase). I will be testing these ideas in the future.
Finally, I am interested in whether a phage (bacterial virus) can control biofilm development. In collaboration with J. Bull and D. Ally, we are testing whether an engineered T7 phage can control E. coli K12 biofilms.
For more details about my biofilm research, click here: Projects/biofilms.
|
|
| research | about me | publications | projects | contact | e-mail |
I am an evolutionary biologist interested in the origins and maintenance of biological diversity. I study evolution in real time, by using evolution experiments with fast-growing microbes. These evolution experiments let me directly test factors that are hypothesized to regulate biological diversity.
Currently, I am studying the evolution of antibiotic resistance in bacterial biofilms as a model system for understanding the process of adaptive radiation in natural and clinical settings.
I am working as a Post Doc with Luke Harmon and Larry Forney, in affiliation with IBEST at the University of Idaho (Moscow, ID, USA).
For my PhD, I studied adaptive diversification in the lab, using the bacterium Escherichia coli. My supervisor was Michael Doebeli at the University of British Columbia in Vancouver, BC, Canada.
For my MSc, I studied the evolutionary ecology of soldier allocation (i.e., defense) in the eusocial aphid, Pemphigus spyrothecae. I worked in the lab of Bernie Roitberg at Simon Fraser University, in Burnaby, BC, Canada.
My BSC honours thesis was on spatial memory, using growth-hormone transgenic mice, in the lab of David Rollo at McMaster University in Hamilton, ON, Canada.
|
|
Publications
| research | about me | publications | projects | contact | e-mail |
10. Tyerman, JG and M Doebeli (submitted) Variation in the propensity to diversify in experimental populations of Escherichia coli: Consequences for adaptive radiation.
9. Tyerman, JG, M Bertrand, CC Spencer, M Doebeli, 2008. Experimental demonstration of ecological character displacement. BMC Evol Biol 8: 9p.
8. Le Gac, M, MD Brazas, M Bertrand, JG Tyerman, CC Spencer, REW Hancock, M Doebeli. 2008. Metabolic changes associated with adaptive diversiÞcation in Escherichia coli. Genetics 178: 1049-60.
7. Spencer, CC, JG Tyerman, M Bertrand, M Doebeli. 2008. Adaptation increases the likelihood of diversiÞcation in an experimental bacterial lineage. PNAS 105: 1585-90.
6. Tyerman, JG, N. Havard, G. Saxer, M. Travisano, M. Doebeli. 2005. Unparallel diversiÞcation in bacterial microcosms. Proc R Soc B 272: 1393-98.
5. Biernaski, J and JG Tyerman. 2005. Commentary: The overextended phenotype. Ecoscience 12: 3-4.
4. Tyerman, JG and Roitberg, BD. 2004. Factors affecting soldier allocation in clonal aphids: A life history model and test. Behav Ecol 15: 94-101.
3. Roitberg, BD, Mondor EB, Tyerman, JG. 2003. Pouncing spider, ßying mosquito: Blood acquisition increases predation risk in mosquitoes. Behav Ecol 14: 736-40.
2. Rollo, CD, CV Ko, JG Tyerman, L Kajiura, 1999. The growth hormone axis and cognition: Empirical results and integrated theory derived from giant transgenic mice. Can J Zool 77: 1874-1890.
1. Roitberg, BD, IC Robertson, JG Tyerman. 1999. Vive la variance: A functional oviposition theory for insect herbivores. Entomologia Experimentalis et Applicata91: 187 - 94.
Please contact me for .pdf reprints or for my CV.
|
|
Biofilms are communities of bacteria that develop at the interface of a surface and a medium. Biofilms occur in natural, industrial, and clinical environments and thus are important to the fields of ecology, engineering, and medicine.
Biofilms are associated with many types of bacterial infections that are of relevance to human health. Some examples of biofilm associated infections include pneumonia in cystic fibrosis patients, middle ear infections in children (otitis media), tooth decay and periodontal disease, and indwelling device infections (catheters, artificial joints, and prosthetic devices). These infections are often difficult to control, and are thus chronic and debilitating (or fatal). What makes these infections so difficult to treat? One factor is that the bacteria that cause the infections are often highly resistant to antibiotic treatment. One of my goals is to understand why and how bacteria in biofilms have evolved this high tolerance to antibiotics.
|
 Do not drink the kool-aid.
|
In the lab, I culture biofilms by growing bacteria in flow-cells, which are basically chemostats that allow bacteria to settle and grow on a glass surface, while media flows through the chamber (see figure).
I am quantifying the amount of heritable varation for antibiotic sensitivity (from resistant to susceptible) -- using Kirby Bauer Disk tests -- within and betwen biofilms cultured in the lab. This involves isolating clones from biofilms at different stages of growth, and assessing individual clones for their sensitivity to a broad array of antibiotics. This work is ongoing.
|
|
Adaptive diversification in E. coli
|
 Colony morphology variation suggests that ecological variation may have evolved within populations of E. coli
|
What factors affect the process of adaptive diversification?
When different populations occupy divergent environments, they often diverge. This process is known as allopatric speciation or incidental diversification. But, can a single population in a heterogeneous environment diversify into subpopulations that each exploit a subset of the niches in the environment? This process is known as sympatric speciation or adaptive diversification. The debate between the importance of allopatric and sympatric diversification (or, adaptive vs. incidental diversification) has a long history and is still unresolved. While it is acknowledged that adaptive diversification can occur, and has occurred, it is not known how often it has contributed to diversity on our planet. In part, this is because little is known about the factors that regulate adaptive diversification.
Using the bacterium Escherichia coli, I tested the role of resource competition in causing populations to diversify in sympatry (Tyerman et al., 2008).
|
Growth curve analysis
When bacteria grow in batch culture, we are often interested in extracting growth curve parameters as resource-related phenotypes. In particular, the maximum growth rate and the maximum yield during a single batch culture growth cycle are often used as measures of fitness.
I've developed R code for analysing microbial batch culture growth curves. Growth Curve Analysis, using R (open ``readme.txt'')
Contact information
| research | about me | publications | projects | contact | e-mail |
Address: Department of Biological Sciences, Life Sciences 252, University of Idaho, P.O. Box 443051, Moscow, ID 83844-3051
Lab: Life Science 282 (Forney lab)
Office: Life Science 275
Phone: +01-(208)-885-4414
Fax: +01-(208)-885-7905
e-mail: jabus@uidaho.edu
|
|
last update: 9/13/09
Go to top | Update notes
|
|
