Definition of Term

Kingdom Prokaryotae (formerly Monera)

(English) Microscopic, prokaryotic cells. Comprise the bacteria, including blue-green bacteria (once considered to be algae). They are characterized by: a lack of membrane-bound organelles such as nuclei, mitochondria, or chloroplasts; the presence of small, distinctive ribosomes; and a single chromosome consisting only of nucleic acid. All major types of metabolism (heterotrophic, autotrophic, etc.) are found in this group. The gene sequence of mRNA molecules is useful for classifying bacterial types. A high degree of phenotypic instability is shown; that is, lines derived from a particular bacterial strain will come to differ from the original after only a few years. Hence, they can be very difficult to classify.

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