Cover photograph (Copyright © 2001, American Society for Microbiology. All rights reserved.): An extruded foregut from a Steinernema carpocapsae nematode showing Xenorhabdus nematophilus bacterial symbionts colonizing the anterior portion of the intestine. The head of an individual nematode was severed with a razor blade, causing the esophagus, basal bulb muscle, and intestine to be extruded from the body. The dissected nematode was stained with crystal violet and viewed with a Nikon Eclipse TE300 inverted microscope at ×1,000 magnification. X. nematophilus colonizes the intestine of the free-living, soil-dwelling stage of the nematode. Together, the nematode and bacterium infect, kill, and reproduce inside larval stage insects. (See related article on page 4687.)