Pulmonale Sequestration

Transformation and transduction to tryptophan independence of strains of Bacillus subtilis carrying the "trpE26" chromosomal aberrations (a translocation and an inversion) with a "normal" 168 type strain as donor induce a tandem duplication of the thrA-ilvA region of the chromosome. The clones possessing this unstable duplication segregate besides the Trp- some stable Trp+ cells which retain only part of the duplication (the trpE-ilvA region) in nontandem configuration. Such clones may also be produced directly during the crosses. The genetic map of these clones (designated as class I stable merodiploids) was constructed: they possess the tranlocation and the inversion of the trpE26 parental strain. Another type of stable Trp+ clones (class II) also appears, although more rarely, in similar crosses. Studies on their genetic structure revealed that they are haploid for the trpE-ilvA region and carry a nontandem duplication of the thrA-trpE region. In these clones the cysB-tre region has the orientation of the 168 type strain. The duplications in both classes are stable, that of class I being more stable than that of class II where loss of one copy of the thrA-trpE region leads to about 1% haploid cells. Detailed genetic studies on heterozygous clones from both classes have shown exchange of alleles between copies of the nontandem duplications. Models are proposed for the formation of each class of merodiploids and for recombination events taking place in them. These models imply recombination at sequences of intrachromosomal homology and (or) introduction of heterologous juncions ("novel joints") by transformation or transduction.

show abstract

“…is phage SP ~3 discovered by WARNER et al. 1977, and extensively studied by ZAHLER and coworkers (ZAHLER et al 1977, ROSENTHAL et aE.…”

Section: Discussionmentioning

confidence: 90%

“…ANAGNOSTOPOULOS 1975, 1976;ANAGNOSTOPOULOS and TROWSDALE 1976;ANAGNOSTOPOULOS 1977). Analogous situations have been encountered in other bacteria and in particular Escherichia coli and Salmonella typhimurium (for reviews see ANDERSON and ROTH 1977;STARLINGER 1977).…”

mentioning

confidence: 71%