A ceiling fan is a mechanical fan, usually electrically powered, suspended from the ceiling of a room, that uses hub-mounted rotating paddles to circulate air.
Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most E. coli are harmless and actually are an important part of a healthy human intestinal tract. However, some E. coli are pathogenic, meaning they can cause illness, either diarrhea or illness outside of the intestinal tract.
In fact, there are more bacterial cells in our digestive tract than there are human cells in our bodies! There are a large number of E. coli strains (or subtypes) with diverse characteristics. Most are harmless to humans, including the B and K-12 strains that are used routinely for laboratory work.