Bacterium

A single-celled, microscopic prokaryotic organism: a single cell organism without a distinct nucleus.

(pl.: bacteria) nicellular prokaryotic organisms, without a distinct nucleus. Major distinctive groups are defined by Gram staining. Also classified on the basis of oxygen requirement (aerobic vs anaerobic) and shape (spherical = coccus; rodlike = bacillus; spiral = spirillum; comma-shaped = vibrio; corkscrew-shaped = spirochaete; filamentous).

More than one bacteria.

A program that attempts to propagate itself by e-mailing a copy of itself to e-mail addresses found on a recipient's hard drive. This is done without the consent or knowledge of the recipient. Note: In many cases, this type of program does not attempt to cause any direct damage to user's system, but rather attempts to overload the e-mail distribution system, much as a successful chain letter would do to the postal system. Synonym [in cryptosystems] chain letter.