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A phylum of pathogens infecting Caenorhabditis nematodes

Wild Caenorhabditis nematodes are commonly found to be infected by many different species of fungal-like pathogens called microsporidia. For one particular genus (Nematocida), nine different species of microsporidia have been found that display some very divergent pathogenic phenotypes when infecting C. elegans. Our lab wants to understand these various divergent pathogenic phenotypes in the context of host interaction and defense. For example, N. displodere and N. homosporus appear to be sister species but infect completely different tissues. Similarly, N. displodere and the newly discovered N. sp. 9 both infect similar tissues but have divergent temperature preferences.

 
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Understanding what restricts pathogen growth to specific tissues

What are the differentiating factors in host tissues that result in intracellular pathogens either thriving or perishing? Our lab wants to understand why one species of pathogen, Nematocida displodere, thrives in the epidermis and muscle but fails to grow successfully in the intestine, while other, closely-related species, Nematocida parisii and Nematocida homosporus, can only grow in the intestine. Using C. elegans, we hope to understand the host and pathogen processes behind tissue-restricted pathogenic growth, especially with regards to tissue-specific innate immunity.

 
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Understanding how temperature affects pathogenesis and host defense or behavior

What role does temperature play in affecting the ability of a pathogen to grow in a host or the ability of the host to defend against the pathogen? Our lab has two related microsporidia pathogens, N. displodere and N. sp. 9, that show similar infection phenotypes (like tissue tropism and spore size) but opposing temperature ranges for growth in the host. We want to study these divergent pathogen phenotypes in C. elegans to better understand what roles host innate immunity and pathogen virulence play in infection, and to investigate whether host behavior can positively or negatively affect on host outcome.

 

Studying bacterial colonization of the intestine

What host and pathogen factors are important for the colonization of the gut epithelia? Our lab studies a variety of new bacterial species found colonizing the intestinal lumen of wild Caenorhabditis nematodes (discovered by Marie-Anne Felix). These bacteria show directional binding to the intestinal epithelial cells, suggesting a direct host/microbe interaction. Using C. elegans, we want to genetically dissect the host and microbe factors responsible for gut colonization and discover the functional consequences of this interaction (pathogenic or commensal). With this we hope to use these bacteria in C. elegans as a model for understanding the molecular and genetic bases for colonization of the gut by extracellular bacteria, and discover ways to disrupt and promote host interaction.

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Sampling wild Caenorhabditis nematodes for new pathogens

We are constantly searching for wild nematodes in and around San Diego State University. We bring rotten fruits and plant stems back to the lab and isolate any nematodes that crawl out. If these nematodes are infected with any new pathogens (bacteria, fungi, microsporidia, or viruses), we isolate and identify them, and then characterize the infection phenotypes. In this manner we plan to study many different natural host/microbe interactions in C. elegans, with the goal to better understand innate immunity, host defense, and pathogen virulence mechanism. (Photo credit: Marie-Anne Felix)

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