Genetic instability in streptomycetes.

Genetic instability is very common in Streptomyces species and is usually due to large chromosomal deletions. In the case of Streptomyces lividans 66, instability can be separated into two steps, each of which involves deletion of over 200 kb of DNA. Extreme DNA amplification often accompanies deletion and in S. lividans 66 this property has been used to amplify cloned genes to obtain stable high-copy-number derivatives.