Genetic instability of the Streptomyces chromosome

Abstract

SummaryThe Streptomyces wild-type chromosome is linear in all examples studied. The ends of the chromosome or telomeres consist of terminal inverted repeats of various sizes with proteins covalently bound to their 5Ј ends. The chromosome is very unstable and undergoes very large deletions spontaneously at rates higher than 0.1% of spores. Frequently, the telomeres are included in the deletions. Loss of both telomeres leads to circularization of the chromosome. The wildtype chromosome can also be circularized artificially by targeted recombination. Spontaneously or artificially circularized chromosomes are even more unstable than the linear ones. High-copy-number tandem amplifications of specific chromosomal regions are frequently associated with the deletions. RecA seems to be involved in the amplification mechanism and control of genetic instability. Spontaneous and induced genetic instability in Streptomyces

Phylogenetic analysis and taxonomic study of marine Cytophaga-like bacteria: proposal for Tenacibaculum gen. nov. with Tenacibaculum maritimum comb. nov. and Tenacibaculum ovolyticum comb. nov., and description of Tenacibaculum mesophilum sp. nov. and Tenacibaculum amylolyticum sp. nov.

“…The genetic variation of gyrB within a species of the Micromonospora genus is very small in comparison with our gyrB data for strains in the CFB complex and the Acinetobacter strains. The reason for such a difference is not clear at present, but it is well known that the chromosome of the actinomycetes is unstable and often undergoes substantial deletion or rearrangement (Volff & Altenbuchner, 1998). Such deletion or rearrangement may reduce the degree of DNA-DNA hybridization much more significantly than the substitution of a single nucleotide.…”

Genomics ofActinobacteria: Tracing the Evolutionary History of an Ancient Phylum

“…strain RHA1, which is not mycelial, is both very large (9.7 Mb) and linear, with telomeres (i.e., chromosome ends) like those of streptomycetes (289). Linear chromosomes have also been reported for a few other bacteria, in which the details of the structures of telomeres, and hence of replication, are different (464). The replication of linear Streptomyces chromosomes and plasmids (70) is initiated from a fairly centrally located replication origin rich in DnaA box sequences and proceeds bidirectionally towards the telomeres (396).…”

Forty years of genetics with Streptomyces: from in vivo through in vitro to in silico

“…The apparent association of deletion and amplification cycles with the end regions of the linear chromosome, although probably not in an obligate way, has recently given the topic a new impetus (e.g. Lin & Chen, 1997 ;Volff & Altenbuchner, 1998).…”