0.2 to 5 microns
50-500 nm
The average size of a bacterium is typically around 1-10 micrometers in diameter. However, some bacteria can be as small as 0.2 micrometers or as large as 750 micrometers.
Bacterium size is measured by a technique called Micrometry. With micrometry you can measured the size of very small beings like bacteria, cells, etc. This technique involves the use of a microscope in which the eye piece is calibrated in micrometers. A similarly calibrated slide is used for standardization. The specimen is then mounted and the size measured. Normally, the size of many cells are taken into account and an average value is taken, since all cells may not be of the same size.
The largest bacterium is Thiomargarita namibiensis, which can have a size of up to 0.75 mm in diameter and up to several millimeters in length.
A virus is much much much smaller then a bacterium. Virus called phage can infect bacteria.
Bacteria are all unicelular, but some live in colonies where they actually don't differ that much in cell size. 'Bacteria' is the plural form of 'bacterium'.
On average, a bacterium is 1 μm or 1 micrometer wide. Hope this helps!
All bacterium is microscopic.
The largest bacterium is Thiomargarita namibiensis, which can reach up to 0.75mm in length, making it one of the largest known bacteria.
Bacteria are generally smaller in size compared to human cells. The average size of a bacterium is around 1-5 micrometers (µm), while the average size of a human cell can range from 10-30 micrometers.
100 times bigger
1.1 to 1.5 µm wide http://www.mansfield.osu.edu/~sabedon/biol2010.htm