Tag: Oral Session 1 O

Tropical land use change effect on soil microbial function

Presenter(s): Sky Ramirez-Doble

Faculty Mentor(s): Krista McGuire & Stephanie Ostresh

Oral Session 1 O

70% of remaining tropical forests, sites with high biodiversity, primary productivity, and CO2 exchange, are being converted into agricultural or logged areas. Tropical agricultural sites have been found with altered levels of soil carbon, nitrogen, and microbial composition; however, anthropogenic effects on soil and litter microbial functional potential are poorly understood. To help reveal the relationship between an altered soil and litter chemistry and microbial functionality, total soil and litter carbon and nitrogen concentrations were correlated with the presence of key decomposition macromolecules in litter and soil in the three most abundant tree species in El Yunque National Forest: Prestoea montana var. acuminate, Casearia arborea, and Dacryodes excelsa. Through a series of statistical tests, we were able to determine if (1) tree species and land use create distinct physical and chemical zones that alter microbial composition and functional potential, (2) differential carbon and nitrogen availability across land use reflects the dominant tree species present, and (3) high land use areas are correlated to earlier successional species such as Casearia arborea and low land use are correlated with late successional species such as Dacryodes excelsa. My research will provide insight into the anthropogenic effects of tropical agriculture.

Examining Pairwise and Multi-Species Interactions in Larval Zebrafish

Presenter(s): Dylan Martins

Faculty Mentor(s): Raghuveer Parthasarathy

Oral Session 1 O

The microbial communities resident in animal intestines are composed of dozens to hundreds of species and play important roles in host health and disease. The determinants of microbial composition, which may include physical characteristics or biochemical interactions, remain largely unknown. Further, it is unclear for many multi-species consortia whether their species- level makeup can be predicted based on an understanding of pairwise species interactions, or whether higher-order interactions are needed to explain community assembly. It is also unclear how spatial organization plays a role in determining the make up of these complex communities. To address this, we consider commensal intestinal microbes in larval zebrafish, initially raised germ-free to allow introduction of controlled combinations of bacterial species. Using a combination of dissection and plating assays and three-dimensional live imaging, we demonstrate the construction of communities of one to five species and test whether outcomes from two-species competitions contain enough information to predict the abundances in more complex communities. We also quantify changes in species’ spatial distributions induced by the presence of other species, which may explain correlations in their abundances. Lastly, we explore the ability of in vitro interbacterial relationships to predict those of the same bacteria in in vivo association.

Determining growth and development in Wyeomyia smithii mosquitoes using fluctuating temperatures

Presenter(s): Danielia Lewis

Faculty Mentor(s): William Bradshaw & Chris Holzapfel-Bradshaw

Oral Session 1 O

Mosquito bites cause over one million deaths per year by spreading blood-borne diseases like malaria, and yellow fever. Synchronous emergence in the spring facilitates males finding mates and also saturating the ability of predators to consume all of the emerging insects (predator satiation). With mass swarming, it ensures that some, or many, of the potential prey will escape predation and reproduce. The ability to predict mass emergence of disease vectors increases the efficacy of control measures, whether by sterile males, toxic baits, or conventional pesticides. Using two northern and two southern populations of the pitcher-plant mosquito, Wyeomyia smithii, I determined the degree of synchronization of development by using realistic, fluctuating temperatures simulating a temperate spring environment. I found that hibernating individuals that started development at warmer temperatures later in the spring developed faster than individuals that started development at cooler temperatures earlier in the spring, both in northern and southern populations. This difference led to later developing mosquitoes “catching up” to those that started development earlier. We call this passive synchronizing effect of warming environments “autosynchronization.” The autosychonization effect was apparent within both southern and northern populations.

These results demonstrate the autosychronization effect, but this effect was not able to synchronize the developmentally conservative northern populations with the more developmentally progressive southern populations, even when encountering the same warming spring environment. The efficient timing of mosquito control efforts will be highly applicable within climatic zones but not between climatic zones due to differences in the developmental physiology of target organisms.

Host-microbe evolutionary antagonism in primates: HopQ’s role as a bacterial adhesin targeting CEACAM1

Presenter(s): Eden Brush

Faculty Mentor(s): Matt Barber

Oral Session 1 O

How animals and microbes interact with each other can mean the difference between harmonious coexistence and deadly infection. These interactions create the potential for evolutionary conflict between host and microbial proteins which can contribute to antagonistic evolution of host and microbial genomes. Specific adhesion to host tissue cells is often a necessary first step in bacterial pathogenesis; “adhesins” are proteins on bacterial surfaces that mediate host cell adhesion and subsequently, invasion and infection. The N-domain of human carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a host protein that modulates cell adhesion and other cell processes, is targeted and exploited by various human- associated bacterial adhesins. The Barber Lab at the University of Oregon has recently discovered that primate CEACAM proteins are rapidly evolving, suggesting an evolutionary ‘arms race’ with the bacterial proteins that target them. One such adhesin is HopQ of Helicobacter pylori. H. pylori is a bacterium that colonizes the stomach of ~50% of the human population worldwide and is the major causative agent for stomach ulcers and gastric cancer. It remains unclear how genetic diversity among adhesins such as HopQ impacts host specificity. We tested our hypothesis that HopQ will bind differentially to various primate CEACAM1 proteins by performing pull-down assays and western blots with H. pylori and recombinant, GFP-tagged, CEACAM1 N domains from a panel of primates. Interestingly, we found that HopQ binds to the N domains of human, chimp, and gorilla CEACAM1. We also found multiple sites of positive selection on HopQ that contact rapidly evolving sites in CEACAM1 lending support to a potential evolutionary ‘arms race’ between the two. These findings are directly applicable to human health, as the host specificity of a pathogen can determine what species are more susceptible to reverse zoonosis, the transfer of a disease-causing agent from humans to animals.