Bacteria

From PLANTFACTS.OSU.EDU

1. microscopic organisms having round, rod-like, spiral or filamentous single-celled or noncellular bodies often gathered into colonies.

The various forms of bacteria.
Source: http://www.sdnhm.org/exhibits/epidemic/teachers/background.html

General Bacteria Diagram
Source: http://www.ou.edu/class/pheidole/bacteria.html