Intestinal bacteria, coloured transmission electron micrograph (TEM). The TEM shows a section through the bacteria (red/yellow) and the wall of the intestines (bottom). The bacteria (Citrobacter sp.) have induced the intestinal cells to form the 'pedestals' (one at centre) on which the bacteria are resting. These pedestals have a concentration of actin microfilaments. Citrobacter bacteria are a normal component of the bacterial population in the human intestines, but some species have been associated with cases of diarrhoea. Magnification: x15,800 when printed 10cm high.