Isolation and characterization of a new restriction endonuclease, Sru30DI, from Selenomonas ruminantium

Anthraquinones quinizarin and danthron unwind negatively supercoiled DNA and lengthen linear DNA

The intercalating drugs possess a planar aromatic chromophore unit by which they insert between DNA bases causing the distortion of classical B-DNA form. The planar tricyclic structure of anthraquinones belongs to the group of chromophore units and enables anthraquinones to bind to DNA by intercalating mode. The interactions of simple derivatives of anthraquinone, quinizarin (1,4-dihydroxyanthraquinone) and danthron (1,8-dihydroxyanthraquinone), with negatively supercoiled and linear DNA were investigated using a combination of the electrophoretic methods, fluorescence spectrophotometry and single molecule technique an atomic force microscopy. The detection of the topological change of negatively supercoiled plasmid DNA, unwinding of negatively supercoiled DNA, corresponding to appearance of DNA topoisomers with the low superhelicity and an increase of the contour length of linear DNA in the presence of quinizarin and danthron indicate the binding of both anthraquinones to DNA by intercalating mode.

Prevalence of CTGCAG Recognizing Restriction and Modification Systemsin Ruminal Selenomonades

Analysis of restriction and modification activities in natural population of Selenomonas ruminantium have revealed the prevalence of CTGCAG (Pst I isoschizomers) recognizing restriction and/or modification systems in these bacteria. Pst I isoschizomeric restriction endonucleases were detected in 4 out of 15 strains tested. In one strain, the Pst I isoschizomeric restriction system was accompanied by another restriction and modification system recognizing GAATTC sequence (Eco RI isoschizomer). Four other strains contained CTGCAG specific methylases which lacked cognate endo-nuclease activities. Presence of identical restriction and modification systems in both of subspecies of S. ruminantium, as well as the occurrence of Pst I isoschizomers in various combinations, indicate the possibility of horizontal transfer of genes coding for these systems.

The rumen microbial ecosystem--some recent developments

The rumen of sheep and cattle represents a mobile, self-sustaining fermentation system for plant material. Analysis of the rumen flora continues to provide fundamental knowledge of anaerobic microbiology and is now yielding microbial genes that have potential in biotechnology. Recent research has provided fascinating glimpses into the microbial enzyme systems that degrade plant material and into the complex interplay among members of the rumen community.