Color enhanced scanning electron microscope (SEM) of salmonella enteritidis. This is a rod-shaped, gram-negative, non-spore forming bacteria primarily adapted to animal hosts. S. enteritidis are considered facultative anaerobes, which means that they propagate in the presence or absence of oxygen. S. enteritidis are propelled through their host's intestines with flagella. These bacteria are currently the leading species of Salmonella that causes illness in the United States. They are capable of infecting hens' eggs in their ovaries. Raw, unpasteurized uncooked eggs pose a health risk. S. enteritidis has recently been discovered to release acyl-homoserine lactone (AHL), which is a chemical that acts as a communication signal between cells. The idea that bacteria cells can communicate chemically is known as quorum-sensing. Image width: 9.14 micrometers. Magnification: 10,940x if printed 10 cm wide.