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Rod-shaped Bacterium Listeria Monocytogenes
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Rod-shaped Bacterium Listeria Monocytogenes

June 22, 2010
Listeria Monocytogenes L. monocytogenes -- a rod-shaped bacterium that moves by means of flagella -- is a carrier of listeriosis, a general name given to the group of disorders caused by the organism, such as meningitis and encephalitis. This image was taken during research performed in the lab of professor Daniel Portnoy, Department of Molecular and Cell Biology, University of California, Berkeley. Dr. Portnoy's research focuses on understanding the molecular and cellular basis of microbial pathogenesis and the mechanisms used by the host to defend against infection. Specifically, the lab is focused on the interaction of the facultative intracellular bacterial pathogen L. monocytogenes and mammalian cells. This fascinating microorganism is able to enter cells, escape from a phagosome and grow rapidly in the cytosol. By exploiting a host system of actin-based motility, the bacteria move through the cytosol to the cell membrane and into pseudopod-like projections (listeriopods) that are ingested by neighboring cells. This mechanism allows pathogens to spread from one cell to another without ever leaving the host cytoplasm thereby avoiding the immune response. (Date of Image: 2000)