POSTDOCTORAL RESEARCH
I studied the evolution of metabolic interactions in microbial communities exposed to fluctuating environments. I investigated two under-explored questions: 1) how does the frequency of fluctuations between conditions affect the community when the interaction network between members changes between conditions? 2) how do evolutionary changes in community members modulate the impact of environmental fluctuations? |
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GRADUATE RESEARCH
I worked on a large-scale evolution experiment in Escherichia coli, which was designed to characterize the diversity of genetic and phenotypic solution to thermal stress. In this experiment, we exposed >100 replicate populations to thermal stress (42.2ºC) for 2000 generations and then measured the relative fitness and complete genome sequence of one isolate from each of 114 high-temperature populations. As a result, we know all of genetic mutations associated with adaptation to thermal stress for these isolates (Tenaillon et al. Science 2012). |
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I built on this experiment by measuring phenotypic variation among the lines and by investigating the functional consequences of individual mutations. The major goals of my dissertation research were to: 1) link phenotypes and fitness with specific mutations (projects 'Antibiotic resistance and stress' and 'Thermal niche evolution') and, 2) identify the functional mechanisms leading to thermal adaptation (project 'Adaptive gene expression changes').
1) ANTIBIOTIC RESISTANCE AND STRESS
EVOLUTION OF RIFAMPICIN RESISTANCE RESULTING FROM HEAT STRESS ADAPTATION
In the first chapter of my dissertation I described the emergence of rifampicin resistant clones that appeared, and were fixed, early in the evolution experiment. The underlying cause of resistance were mutations within the rpoB gene encoding the beta subunit of RNA polymerase. These mutations were highly beneficial at high temperature and low glucose. Their fitness effects depended on the environment and genetic background, providing glimpses into the prevalence of epistasis and pleiotropy (Rodriguez-Verdugo et al. BMC Evolutionary Biology 2013).
EVOLUTION OF RIFAMPICIN RESISTANCE RESULTING FROM HEAT STRESS ADAPTATION
In the first chapter of my dissertation I described the emergence of rifampicin resistant clones that appeared, and were fixed, early in the evolution experiment. The underlying cause of resistance were mutations within the rpoB gene encoding the beta subunit of RNA polymerase. These mutations were highly beneficial at high temperature and low glucose. Their fitness effects depended on the environment and genetic background, providing glimpses into the prevalence of epistasis and pleiotropy (Rodriguez-Verdugo et al. BMC Evolutionary Biology 2013).
2) THERMAL NICHE EVOLUTION
GENETIC BASES OF FITNESS TRADE-OFFS
In the second chapter of my dissertation, I explored the phenotypic consequences of thermal adaptation. I asked whether adaptation to high temperature entails a fitness trade-off at low temperature. I characterized the thermal growth curve of 114 high-temperature adapted clones and I found that there were (broadly speaking) two phenotypes: evolved clones with expanded thermal niches and evolved clones that had shifted their niche toward high temperatures. These two phenotypes were associated with single mutations in the two major adaptive pathways, one which was typified by mutations in RNA polymerase and the other by mutation in the Rho termination factor.
GENETIC BASES OF FITNESS TRADE-OFFS
In the second chapter of my dissertation, I explored the phenotypic consequences of thermal adaptation. I asked whether adaptation to high temperature entails a fitness trade-off at low temperature. I characterized the thermal growth curve of 114 high-temperature adapted clones and I found that there were (broadly speaking) two phenotypes: evolved clones with expanded thermal niches and evolved clones that had shifted their niche toward high temperatures. These two phenotypes were associated with single mutations in the two major adaptive pathways, one which was typified by mutations in RNA polymerase and the other by mutation in the Rho termination factor.
3) ADAPTIVE GENE EXPRESSION CHANGES
MOLECULAR MECHANISMS OF THERMAL ADAPTATION
My third chapter focused on identifying the molecular mechanisms leading to thermal stress adaptation. I studied the functional consequences of mutations in the rpoB gene, based on information of gene expression (mRNAseq) and measurements of transcription efficiency of the RNA polymerase.
MOLECULAR MECHANISMS OF THERMAL ADAPTATION
My third chapter focused on identifying the molecular mechanisms leading to thermal stress adaptation. I studied the functional consequences of mutations in the rpoB gene, based on information of gene expression (mRNAseq) and measurements of transcription efficiency of the RNA polymerase.
UNDERGRADUATE RESEARCH
During my undergraduate studies I got involved in several microbial ecology projects. These studies described the diversity of bacteria living in the aquatic system of Cuatro Cienegas, Coahuila located in the north of Mexico.
In my bachelor of science thesis I investigated the seasonal diversity of several species of the genus Pseudomonas from an evaporating lagoon in Cuatro Cienegas basin. My most significant result was to observe a seasonal pattern of isolates occurrence.
RELATED PUBLICATION:
During my undergraduate studies I got involved in several microbial ecology projects. These studies described the diversity of bacteria living in the aquatic system of Cuatro Cienegas, Coahuila located in the north of Mexico.
In my bachelor of science thesis I investigated the seasonal diversity of several species of the genus Pseudomonas from an evaporating lagoon in Cuatro Cienegas basin. My most significant result was to observe a seasonal pattern of isolates occurrence.
RELATED PUBLICATION:
- Rodríguez-Verdugo A., V. Souza, L.E. Eguiarte, and A.E. Escalante. 2012. Diversity across seasons of culturable Pseudomonas from a dessication lagoon in Cuatro Cienegas, Mexico. International Journal of Microbiology. doi:10.1155/2012/201389