Is bacteria a single celled organism?

A unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell, unlike a multicellular organism that consists of more than one cell. Unicellular organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Prokaryotes include bacteria and archaea. read more

Algae are photosynthetic organisms that can be multicellular or single-celled. Single-celled algae include pond organisms like Chlamydomonas and ocean plankton like diatoms, which are unicellular but sometimes exist as colonies that form beautiful shapes when viewed under a microscope. read more

As well as simple bacteria, there are more complex organisms, known as protoctists. Unlike bacteria, they have complex internal structures, such as nuclei containing organized strands of genetic material called chromosomes. Most are single-celled, but some form colonies, with each cell usually remaining self-sufficient. read more