Actinobacillus bacteria. Coloured transmission electron micrograph (TEM) of a section through Actinobacillus actinomycetemcomitans bacteria. The bacteria (also known as Actinobacter) are grouped together after being cultivated in the laboratory. These rod-shaped bacteria are bound together by their pili (dark lines). Pili are hair-like appendages of which there may be hundreds on an individual bacterial cell. Cell contents can be seen inside the bacteria. Actinobacillus actino- mycetemcomitans can cause periodontitis & subacute endocarditis in humans. Treatment is usually with antibiotics. Magnification: x30,000 at 6x7cm size. x100,000 at 8x10"~LANDSCAPE"