An intracellular bacterium filaments to spread to neighboring intestinal cells
We found a new species of bacteria that forms long filaments inside the intestinal cells of its host. These filaments allow the bacterium to spread to neighboring intestinal cells in a unique mechanism of cell-to-cell spreading. We named this bacterium Bordetella atropi, in honor of Atropos, the Greek Fate who cuts the thread of life .
We want to determine what B. atropi detects inside of a host intestinal cell that tells it to change morphology. Currently, we believe that the bacteria detects the very nutrient rich environment of the cell to trigger it to become filaments. This is because if we delete genes involved in utilization of excess glucose, the bacterium loses the ability to form filaments inside host cells.
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.
Live C. elegans animal expressing GFP in the intestinal cells (green) and colonized in the lumen with an adhering bacteria (Lelliottia jeotgali) expressing tdTomato (red). Image credit, Dalaena Rivera
Model of bacterial species competing for adhesion to host intestinal cells, with the hypothesis that host responses can positively regulate commensal (L. jeotgali) over pathogenic (LUAb1) bacterial adherence. Image credit, Dalaena Rivera.
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)
Image credit, Marie-Anne Felix