Immunofluorescent micrograph of spirochaete (spiral-shaped) bacteria Borrelia burgdorferi, that causes Lyme disease. These bacteria are passed to humans through the bites of infected Ixodes sp. ticks. Symptoms of Lyme disease include skin lesions, muscle pain, neurological and cardiac abnormalities, and arthritis. B. burgdorferi changes the expression of its outer proteins depending on the host. Here, spirochaetes that express outer surface protein D were identified using immunofluorescent antibodies (yellow and orange). This was then merged with an image showing all other spirochaetes, labelled using anti-B.burgdoferi antibodies (green).