The structure of the transposable genetic element ISBsu2 in the cryptic plasmid p1516 from a soil Bacillus subtilis strain and the presence of homologues of this element in the chromosomes of various Bacillus subtilis strains

A cryptic plasmid from a soil strain of Bacillus subtilis was found to contain a sequence having features of IS element. Homologous sequences were also found in the chromosome of this strain and in the chromosomes of some other B. subtilis strains.     

Plasmid deletion formation between short direct repeats in Bacillus subtilis is stimulated by single-stranded rolling-circle replication intermediates

Summary The effects of the rolling-circle mode of replication and the generation of single-stranded DNA (ss DNA) on plasmid deletion formation between short direct repeats in Bacillus subtilis were studied. Deletion units consisting of direct repeats (9, 18, or 27 bp) that do or do not flank inverted repeats (300 bp) were introduced into various plasmid replicons that generate different amounts of ss DNA (from 0% to 40% of the total plasmid DNA). With ss DNA-generating rolling-circle-type plasmids, deletion frequencies between the direct repeats were 3- to 13-fold higher than in plasmids not generating ss DNA. When the direct repeats flanked inverted repeats the deletion frequencies in ss DNA-generating plasmids were increased by as much as 20- to 140-fold. These results support models for deletion formation based on template-switching errors during complementary strand synthesis of rolling-circle-type plasmids. The structural instability (deletion formation between short direct repeats) of the ss DNA-generating plasmid pTA1060 in B. subtilis was very low in the presence of a functional initiation site for complementary strand synthesis (minus origin). This observation suggests that it will be possible to develop stable host-vector cloning systems for B. subtilis.     

Ca2+-induced fusion of cardiolipin/phosphatidylcholine vesicles monitored by mixing of aqueous contents

The kinetics of Ca²⁺-induced fusion of large (0.1 μm) unilamellar cardiolipin/phosphatidylcholine (1:1) vesicles have been investigated by continuous monitoring of the mixing of the aqueous vesicle contents. In parallel, release of vesicle contents to the external medium has been followed. Initial fusion of the vesicles is non-leaky, release of vesicle contents being largely a secondary phenomenon. The minimal Ca²⁺ concentration required for fusion in this system is approx. 9 mM. At higher Ca²⁺ concentrations fusion is extremely fast, occurring on the time scale of seconds.     

The Structure of the Transposable Genetic Element ISBsu2 from the Cryptic Plasmid p1516 of a Soil Bacillus subtilis Strain and the Presence of Homologues of This Element in the Chromosomes of Various Bacillus subtilis Strains

A cryptic plasmid from a soil strain of Bacillus subtiliswas found to contain a sequence having features of an IS element. Homologous sequences were also found in the chromosome of this strain and in the chromosomes of some other B. subtilis strains.