Recent Projects
Phytoplankton population demographics
Quantifying mortality and dormancy rates in temperature changes
Phytoplankton play a key role in the global carbon cycle and in sustaining marine ecosystems. They are experiencing thermal perturbations that are more extreme and frequent than ever before due to anthropogenic climate change. It is imperative to develop accurate and empirically grounded ecological models to predict the impact of such environmental changes on phytoplankton populations. Currently, essential data on how temperature affects key demographic rates (including mortality and dormancy) of phytoplankton are lacking. Estimating these rates requires tracking the fate of the individual phytoplankton. I developed a novel approach to examine phytoplankton population composition using flow cytometry. Using this technique, I aim to answer the following questions:
1.How do temperature-dependent stress and mortality affect phytoplankton populations and limit their spatial and temporal distribution?
2.How effective is dormancy as a means of surviving heatwaves and acute stress?
Antibiotics and the environment
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Temperature effects on antibiotic efficacy and the evolution of resistance
The interplay between antibiotics and temperature shifts is now beginning to be further investigated. I have highlighted the physiological and genetic similarities, the possible effects of global climate change, and how it can affect the global health concerns of antibiotic resistance (Rodríguez-Verdugo et al. 2020). I also examined the interactions between changes in temperature and antibiotic use. Through this method, we were able to suggest and support the idea that the bacterial response to some antibiotics is actually a co-opted thermal response (Cruz-Loya et al., 2019). By developing a model to determine the optimal temperature, we found that the optimal temperature systematically shifts in the presence of certain antibiotics (Cruz-Loya et al., 2021). Other projects have examined how the adaptation of antibiotic resistance affects the optimal temperature (Mira et al., 2022), and the optimal temperature shifts after adaptation to heat stress.
Evolution of antibiotic resistance
Cross-Resistance, Collateral Sensitivity, Antibiotic Interactions, and Their Influence on Antibiotic Resistance Evolution in Bacteria
The prevalence and strength of multi-drug antibiotic resistance have resulted in an arms race between the development of new treatment options and the evolution of resistance in bacteria. Combination drug therapies and antibiotic cycling are possible solutions to this problem. However, these solutions present new challenges. I used experimental evolution to broaden our understanding of the evolution of resistance to combinations of multiple antibiotics. I found that the range of antibiotic concentrations that can select for resistant mutants widens once resistance has evolved (Gianvecchio et al., 2019 and Lozano-Huntelman et al., 2020). In addition, this work investigated how the genetic background of resistant strains affects the viability of four effective 3-drug combinations and each of the individual drugs that make up the combination (Lozano-Huntelman et al., 2023). This work also evaluated the presence and persistence of an understudied type of drug interaction, hidden suppression, in 3-, 4-, and 5- drug combinations (Lozano-Huntelman et al., 2021). Hidden suppression occurs when the combined effects of multiple antibiotics result in more bacterial growth than the effects of a smaller subset of those same antibiotics. Finally, this work asked if the drug interactions within a 3-drug combination can affect the rate at which resistance evolves in Staphylococcus epidermidis (submitted). Using a microbial system to study the evolution of antibiotic resistance allows me to help solve public health crises while addressing fundamental questions in evolutionary biology.
