Mitochondrial heredity of resistance to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, an inhibitor of cytochrome b oxidation, in Saccharomyces cerevisiae.

3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), an inhibitor of cytochrome b oxidation, has been used for the selection of three resistant mutants (diur) of Saccharomyces cerevisiae. The mutant diur-64 exhibits in vivo cross-resistance to antimycin A while diur-34 and diur-1 are more sensitive to antimycin A than the parental strain. The three mutants exhibit mitochondrial inheritance according to the following criteria: mitotic segregation of diuron-resistant and diuron-sensitive diploids is obtained among the diploid progeny of a cross between diur and dius; non-Mendelian segregation of diuron resistance (4:0) is observed in spores of tetrads issued from diuron-resistant diploid; extensive ethidium bromide treatment leads to the formation of Q- mutants which no longer transmit diur and dius alleles. Evidence for two distinct diuron-resistant loci were obtained by allelism tests. Recombination analysis shows that diuron-resistance is not located in the polar region of the mitochondrial genome. The diur loci are not linked to the erythromycin locus since the upper limit in recombinants frequency (26%) for a non-polar region is obtained between diur and eryr. A low recombinants frequency (3%) is observed in crosses between diur-34 mutation and the two mutants cob1 and cob2 suggesting that diur-34 might be located between these two cytochrome-b-deficient loci. The resistance to diuron is also expressed in vitro since the oxidation rates of succinate by sonicated submitochondrial particles from the mutants are clearly less sensitive to diuron than that of the wild type.     

Presence and Analysis of Plasmids in Human and Animal Associated Arcobacter Species

In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration.     

In vitro differentiation of inflammatory and non-inflammatory states of the synovial fluid by magnetic protonic relaxation

The differentiation between inflammatory and non inflammatory states has been performed using Nuclear Magnetic Resonance (NMR) in vitro by measuring relaxation times T1 and T2 in 84 synovials fluids obtained from various rheumatologic diseases. The results show that the T1/T2 ratio is more sensitive to distinguish these two situations rather than the isolated T1 or T2 values. In particular, high values of T1/T2 ratio are found in septic arthritis.     

Dynamics of long-leaved sundew Drosera intermedia populations at two extremes of a hydrological gradient

Densities of Drosera intermedia were low in two studied habitats (10–25 ramets m⁻¹), a path through a wet heath (short inundation in spring, low soil moisture in summer) and a pool edge (longlasting inundation, high soil moisture in summer). The low densities could be explained by the observed low recruitment and high adult mortality.
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality.     

A locus involved in kanamycin, chloramphenicol and L-serine resistance is located in the bglY-galU region of the Escherichia coli K12 chromosome

Summary Spontaneous mutants of Escherichia coli K12 displaying an increased level of the kanamycin resistance conferred by plasmid pGR71 were selected. Several mutants obtained in this way apparently carry large chromosomal deletions extending into galU and/or bglY (27 min). This positive selection of deletions allowed detection of a new locus located between galU and bglY. Deletions of this locus are responsible for increased resistance to kanamycin (Irk), decreased resistance to l-serine in minimal medium (Drs) and decreased resistance to chloramphenicol (Drc) when a cat gene is present in the bacteria.     

Molecular recognition between oligopeptides and nucleic acids. DNA sequence specificity and binding properties of an acridine-linked netropsin hybrid ligand

The binding to DNA of a mixed function ligand (NETGA) is described, in which a potential intercalating group, an acridine moiety, is incorporated at the carboxyl terminus of the minor groove binding oligopeptide netropsin skeleton. Scatchard analysis of absorption data provided evidence of two modes of binding to DNA with K1 = 9.1 x 10(5) M-1 at low r values (0.003-0.1), and a binding site size n = 10, indicative of binding of both moeities. At high binding ratios (greater than 0.1), K2 = 0.9 x 10(5) M-1 and n = 5 corresponding to external binding. Complementary strand MPE footprinting on a pBR322 restriction fragment showed NETGA binds to 5'-AAAT like netropsin. It causes enhanced cleavage by MPE, particularly at G-C rich sequences and remote from the preferred binding sites. Viscometry measurements provided evidence for biphasic modes of the two binding portions of NETGA. Fluorescence polarization and linear dichroism measurements were in accord with distinct modes of interaction of the acridine (intercalation) and oligopeptide (minor groove binding) portions of NETGA. LD measurements on NETGA indicate that the oligopeptide moiety (netropsin-like) has an orientation typical of minor groove binders, whereas the degree of intercalation of the acridine group is decreased by association of the oligopeptide moiety.     

The reproductive behaviour of a clonal herbaceous plant, the longleaved sundew Drosera intermedia, in different heathland habitats

The reproductive behaviour of the longleaved sundew Drosera intermedia Hayne was studied in three hydrologically differing heathland habitats a pool edge, an old path through the wet heath and a seepage area
Sexual reproductive allocation (SRA) (the slope of the regression of sexual biomass on vegetative biomass m a given season) differed strongly between years (related to temperature and precipitation) and habitats Averaged over years, path plants had a higher SRA than plants in the seepage area and at the pool edge
Asexual reproductive allocation, expressed as the size-dependent probability of reproducing asexually, did not differ between habitats in most years
The observations agreed with general life history theory SRA was high in the path habitat where adult survival chances were low and juvenile (= seed, first year seedling) survival was high SRA was lower in the seepage area where adult survival chances were higher and juvenile survival lower At the pool edge, a habitat with high adult mortality and low juvenile establishment, the predicted optimal reproductive behaviour, a high SRA, was not observed due to environmental constraints (inundation)