Integrated and Free State of Plasmids
It is a well documented fact that many (if not all) bacteria have but one chromosome (one continuous DNA molecule) forming a single linkage group containing all of the essential genes of the cell. Recently however one has realized that many bacteria in fact contain one or more additional DNA structures usually carrying so called facultative genes that are only essential to the cell’s survival under particular circumstances (e.g. antibioticum resistance transfer factors) so that they can be gained or lost without lethal effect for the cell. Furthermore these “extrachromosomal” DNA molecules are usually significantly smaller than the chromosomal DNA.
KeywordsHost Chromosome Extrachromosomal Element Single Linkage Group Transmissible Plasmid Multiple Drug Resistant Bacterium
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