Bacterium

A bacterium is a unicellular micro-organism without a nucleus (prokaryote) whose genome is formed from DNA. The bacterium contains a single chromosome and may contain plasmids.

Some bacteria can be pathogenic. The symptoms of bacterial infection in human beings are similar to those of viral infection (skin rash, cough, nasal drip, tear formation, tiredness, nausea, temperature, and muscle pain). Bacterial infections are treated with antibiotics.