Microbes in Space

In the late 1990s, NASA decided to join the Russian space program in its evaluation of the microbial activity aboard Mir. NASA wanted to learn about the kinds of organisms that can grow in  spacecraft occupied for long periods of time and where air and water are  recycled.
When they opened a rarely-accessed service panel in Mir's Kvant-2 Module and discovered a large free-floating mass of water. Samples extracted from the globules by syringes and returned to Earth  for analysis contained several dozen species of bacteria and fungi, plus  some protozoa and dust mites.
Aboard Mir, colonies of organisms were also found growing on "the rubber  gaskets around windows, on the components of space suits, cable  insulations and tubing, on the insulation of copper wires, and on  communications devices," says Andrew Steele, scientist at the Carnegie  Institution of Washington working with other investigators at the  Marshall Space Flight Center In Alabama. Aside from being unattractive or an issue for human health, microorganisms can attack the structure of a spacecraft itself. In short, germs can be as bad for a spacecraft's health as for crew health.