what is a bacteriam

A bacterium is the singular form of the plural word "bacteria". To put it another way, you use "bacterium" when there is only one of them and only use the word "bacteria" if you are refering to more than one. Many people get this wrong and you often see a phrase such as "a bacteria can cause disease" when of course it should be "a bacterium can cause disease".

A bacterium is a living cell consisting of a fluid called cytoplasm enclosed by a cell membrane and cell wall. A bacterium contains DNA in the cytoplasm in the form of a chromosome. Although a bacterium only has one chromosome it can have other, smaller DNA elements called plasmids. The chromosome of a bacterium is never surrounded by a nuclear membrane and this fact defines a bacterium as a prokaryote. Organisms that have their DNA in a nucleus surrounded by a nuclear membrane are called eukaryotes. A bacterium also has ribosomes in the cytoplasm. Ribosomes are involved in making proteins.