For more information on these projects see the Publications tab where PDFs for each peer-reviewed publication are available, or send me an email!
Current Projects
Parasitism & Predation: Microbial interactions in the coral holobiont
Photo: Justin Smith
Mechanisms of bacterial predation
Microbiomes perform critical functions for their hosts and in recent years evidence has revealed the importance of both bottom-up and top-down forces in structuring microbial communities. Although predation is a known top-down regulator of ecosystem integrity, resilience, and evolution in plants and animals, we know much less about predation within microbiomes. In this project I am using lab-based assays and bioinformatic analyses to explore the ecology of a ubiquitous, yet poorly understood marine bacterial predator, Halobacteriovorax.
Welsh et al., 2017
Rickettsiales in Caribbean Acropora (RICA)
Coral microbiomes are complex, dynamic communities that provide essential functions for the coral holobiont. Disruption of these communities due to environmental stressors can alter microbiome structure and function resulting in dysbiosis and disease. The novel coral symbiont Aquarickettsia rohweri has emerged as an abundant, nutrient-responsive parasite that has a significant and negative impact on host fitness. Using samples collected from a field experiment in the Florida Keys by the Vega Thurber Lab, my contribution to this work aims to understand gene expression and localization of A. rohweri within Acropora host tissue.
Type VI secretion competition in the Vibrio-Squid Symbiosis
Photo: Andrew Cecere
Conditional regulation of the Vibrio fischeri T6SS
Bacteria experience dramatic changes in their environment as they transition from free-living to host-associated states. These host cues can act as signals to cells to alter their behavior and enhance their fitness for a host niche. Because space within desirable host colonization sites is limited, bacteria have evolved diverse strategies to compete with other potential colonizers and resident communities. The type VI secretion system (T6SS) is a broadly-distributed competitive mechanism that is important in structuring host-associated communities. My research explores how environmental and host-specific conditions (viscosity, salinity, pH, & calcium) modulate the T6SS in Vibrio fischeri light organ symbionts.
Factors mediating contact-dependent killing in a liquid environment
Bacteria employ contact-dependent competitive mechanisms that require an inhibitor cell to physically interact with a target cell to deliver effectors. Such strategies may be particularly useful in liquid environments where diffusible antimicrobial molecules can become quickly diluted. However, how inhibitor cells mediate contact and discriminate between possible target cells remains largely unknown. My work uses both a targeted mutation approach and an unbiased, genome-wide analysis to investigate essential genes for target selection and T6SS-killing in liquid environments using the bioluminescent marine bacterium Vibrio fischeri.
Previous Projects
Symbiont transmission in shipworms
Intracellular symbionts live within specialized host cells called bacteriocytes where they perform vital functions for their hosts. However, relatively little is known about host-intracellular symbiont interactions because these relationships are often obligate (neither organism can survive without the other) and are therefore tricky to study in the lab. I am working with collaborators in the Distel Lab to investigate intracellular symbiont transmission in the wood-boring shipworm species complex Lyrodus pedicellatus.
