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Four Transfer Factors in a Single Bacterial Strain

Naturevolume 214pages414415 (1967) | Download Citation



A NEW class of genetic elements, termed episomes1, has been recognized in bacteria. Episomes are accessory cell components which may or may not be present in any individual organism, and they are characterized by the ability to exist in a bacterium in either one of two states: as an integrated addition to the bacterial chromosome (with which the episome divides in synchrony), or as an autonomous, independently replicating, cytoplasmic inclusion. In the latter state, episomes replicate more rapidly than the host chromosome and can be transmitted at high frequency to other cells, without associated chromosomal transfer. Herein resides the importance of these structures, because an entire bacterial population can rapidly acquire one or more new heritable traits through infection from a cell carrying an episome.

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  1. Department of Microbiology, Johns Hopkins University School of Medicine, Baltimore, Maryland

    •  & E. ELLEN NELL


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