Biomedical subjects

V Vagner

Publications and source records attributed to V Vagner.

5 recordsLinked to original sources

PubMed2003

Essential Bacillus subtilis genes.

To estimate the minimal gene set required to sustain bacterial life in nutritious conditions, we carried out a systematic inactivation of Bacillus subtilis genes. Among approximately 4,100 genes of the organism, only 192 were shown to be indispensable by this or previous work. Another 79 genes were predicted to be essential. The vast majority of essential genes were categorized in relatively few domains of cell metabolism, with about half involved in information processing, one-fifth involved in the synthesis of cell envelope and the determination of cell shape and division, and one-tenth related to cell energetics. Only 4% of essential genes encode unknown functions. Most essential genes are present throughout a wide range of Bacteria, and almost 70% can also be found in Archaea and Eucarya. However, essential genes related to cell envelope, shape, division, and respiration tend to be lost from bacteria with small genomes. Unexpectedly, most genes involved in the Embden-Meyerhof-Parnas pathway are essential. Identification of unknown and unexpected essential genes opens research avenues to better understanding of processes that sustain bacterial life.

Bacillus subtilis↗

PubMed1992

Efficiency of homologous intermolecular recombination at different locations on the Bacillus subtilis chromosome.

The efficiencies of intermolecular recombination at 12 different locations on the Bacillus subtilis chromosome were determined by transforming competent cells with a nonreplicative plasmid. The efficiencies varied by only about threefold but were significantly different (P less than 0.05 by a chi-square test) for approximately 20% of the locations. The recA gene product is required for recombination, and the addA gene product appears to affect the variation in a site-specific way.

Bacillus subtilis↗

PubMed1990

Direction of DNA entry in competent cells of Bacillus subtilis.

Direction of DNA entry in Bacillus subtilis competent cells was studied using molecules in which only one of the two strands was radioactively labelled. The label was either distributed homogeneously or was localized in a small region of the strand, in the centre or at one of the ends. Regardless of the distribution and the position of the label, similar amounts of radioactivity were taken up by the cells exposed to the labelled molecules. This suggests that DNA enters B. subtilis either by two different uptake systems having opposite polarities, or by a single non-polar system.

Bacillus subtilis↗

PubMed1988

Efficiency of homologous DNA recombination varies along the Bacillus subtilis chromosome.

Structures consisting of a genetic marker (erythromycin or kanamycin resistance, thymidylate synthetase) flanked by 3.4-kilobase direct repeats (pBR322 sequences) were inserted in 12 different locations of the Bacillus subtilis chromosome. Recombination between the repeats was followed by the loss of the genetic marker. Recombination frequencies found in different locations varied from 1.2 X 10(-5) to 40 X 10(-5) per cell generation. Such differences were highly significant (P less than 0.001).

Bacillus subtilis↗

PubMed1985

Activation and inhibition of transcription by supercoiling.

Stimulation of transcriptional activity in vitro is observed at low and moderate negative superhelical densities up to the level of the natural superhelical form of the plasmid pBR322. We have isolated and identified three specific transcription products: ampicillinR RNA, tetracyclineR RNA and "Rep" RNA. Their enhancement of transcription occurs at different levels of superhelicity, suggesting a sequence-dependent structural alteration of promoters upon changes of axial writhe, which may generate kink formation. The activation of transcription is drastically inhibited at higher specific linking differences exceeding that of the natural superhelical form of pBR322, which is correlated with a transition from the right-handed B to a left-handed DNA form of particular sequences induced by supercoiling. We have identified a new stop point in the beta-lactamase coding sequence composed of eight alternating purine-pyrimidine residues which, at higher torsional stress, causes transcription to stop, leading to the synthesis of a short RNA of about 55 nucleotides instead of AmpR RNA (about 580 nucleotides). In the "Rep" promoter, two alternating purine-pyrimidine segments are found, which conformational change at higher superhelical densities may be implicated in repression of "Rep" RNA synthesis. The enhancement and inhibition of transcription by supercoiling support the role of energetic and structural changes in topologically constrained DNA as elements of a control mechanism.

Autoradiography↗