Artificial circularization of the chromosome with concomitant deletion of its terminal inverted repeats enhances genetic instability and genome rearrangement in Streptomyces lividans |
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Authors: | J-N Volff P Viell and J Altenbuchner |
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Institution: | (1) Institut für Industrielle Genetik, Universit?t Stuttgart, Allmandring 31, D-70569 Stuttgart, Germany, DE |
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Abstract: | The unstable linear chromosome of Streptomyces lividans was circularized by homologous recombination and its terminal inverted repeats deleted. Strains with circularized chromosomes
showed no obvious phenotypic disadvantages compared to the wild type. However, they segregated about 20 times more chloramphenicol-sensitive
mutants than the wild type (24.3% vs. 1.4%), due to a higher incidence of large deletions. In addition, in all circularized
chromosomes amplification of 30–60 kb fragments was observed at the new chromosomal junction, to levels of approximately 10
copies per chromosome. Arginine auxotrophs that arose spontaneously among the progeny of strains with a circularized chromosome
showed high-copy-number amplification of the DNA element AUD1, as also seen in mutants of the wild type. These observations
demonstrate that the circular form of the Streptomyces chromosome is more unstable than the linear one.
Received: 28 July 1996 / Accepted: 18 November 1996 |
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Keywords: | Streptomyces Circularized chromosome Genetic instability Deletions DNA amplification |
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