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Definition: prokaryote from Processing Water, Wastewater, Residuals, and Excreta for Health and Environmental Protection: An Encyclopedic Dictionary

Any cellular organism in which the nucleus has no limiting membrane, mitochondria, or plastids; a simple life form of a diverse group that includes bacteria, blue-green algae (cyanobacteria), and archaea. Also spelled procaryote. See also eukaryote.

Summary Article: prokaryote
From Dictionary of DNA and Genome Technology

Any organism – limited to species of the ARCHAEA or BACTERIA – whose cellular structure is characterized by the absence of a nuclear membrane and the absence of organelles such as mitochondria. (cf. EUKARYOTE.) There are other basic differences that distinguish prokaryotes from eukaryotes, e.g. differences in ribosome structure, and translation factors etc.; in the enzymes that act on nucleic acids; in proteasomes; in membrane lipids; in various aspects of metabolism; and, not least, in the general organization of the genome.

The typical prokaryotic genome is a circular dsDNA molecule (chromosome) present in one or more copies, depending on species and on growth temperature. Prokaryotes typically have only one type of chromosome, but cells of e.g. Vibrio cholerae contain two dissimilar chromosomes which (jointly) constitute the genome of the species [Nature (2000) 406:477–483]. (See also NUCLEOID.)

Some prokaryotic chromosomes are not ccc dsDNA. For example, the chromosomes are molecules of linear dsDNA in the bacterium BORRELIA BURGDORFERI and in species of e.g. Rhodococcus and Streptomyces.

© 2013 by Paul Singleton

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