Click here to see a JPEG of this microbe
Nitrosomonas europaea is an "ammonia-powered" microbe that uses ammonia as a fuel to live and grow. Power generating membranes (long, thin tubes inside the cell) use electrons from ammonia's nitrogen atom to produce energy. In this image, created with a transmission electron microscope, we can see the interior of one of this microbe's cells. The semi-transparent, roughly circular area towards the top of this image (just left of center) is a cross-section of one of the bacteria. The dark lines circling much of the interior of the cell are the power generating membranes that process the ammonia. The cell to the right is more heavily stained, so it appears dark and reveals less internal structure.
Nitrosomonas europaea can obtain the carbon that it needs to grow by getting it from the atmosphere in a process known as "carbon fixation". Carbon fixation is the process of converting carbon in a gaseous form into carbon bound up in organic molecules. This bacterium contains "carboxysomes" (dark spots which can be seen scattered throughout the cell), which store the enzymes used to fix carbon dioxide for cell carbon. You may recall that plants can fix carbon, that is, they can convert carbon dioxide into sugar, using the energy from photosynthesis. This strange bacterium can also fix carbon, but instead of photosynthesis for its energy it uses the energy produced by "burning" ammonia with oxygen. N. europaea must consume large amounts of ammonia before it will divide, and cell division may take up to several days. This microbe, which does not like being exposed to light, will cover itself in slime and form clumps with other microbes to avoid it.
Some ammonia-chomping microbes can live in the walls of buildings and on the surfaces of monuments, especially in polluted areas where air contains high levels of nitrogen compounds. When these microbes use ammonia from the air, they produce nitric acid. The acid can cause dissolve some stone and other construction materials found on statues and in buildings.