Oral ingestion of Microbacterium nematophilum leads to anal-region infection in Caenorhabditis elegans

Microbacterium nematophilum is a gram positive bacterium that colonizes the Caenorhabditis elegans rectal region causing swelling and constipation. This interaction has been exploited as a model system to identify and study genes important in host–pathogen interactions and innate immunity. During attempts to inhibit the host–pathogen interaction, it became important to clarify the route of infection. Using bacteria labeled with the fluorescent dye Cy3, we show that infection is via the oral route only and that infection follows a clear pattern of ingestion, plug formation, and bump development that can be quantitatively tracked over time.