Individual patterns of immediate skin reactivity to mold extracts.

One hundred atopic patients were skin tested intradermally over a 2-year period with 30 different mold extracts. Subjects were monitored for immediate reactions. Data suggest that to evaluate mold sensitivity in atopic patients one must use multiple mold extracts.

Characterization of siderophores from Ustilago maydis.

Two siderophores, ferrichrome and ferrichrome A, were found in cultures of Ustilago maydis (DC) Corda. Both siderophores were found intracellularly and extracellularly. Their authenticity was confirmed by thin layer chromatography, HPLC, UV-visible spectrometry, paper electrophoresis, amino acid analysis, NMR and fast atom bombardment mass spectroscopy. Regulation of siderophore production by iron was examined. Repression of biosynthesis of extracellular siderophores occurred at 10(-5) M iron. Ferrichrome was found intracellularly at all iron concentrations employed; in general, ferrichrome A was not found to be cell-associated.

Two Ustilago maydis viral dsRNAs of different size code for the same product.

UmV is a double-stranded RNA (dsRNA) virus of the corn fungus Ustilago maydis. There are three viral subtypes, P1, P4 and P6, which differ in the specificity of their secreted killer toxins. Each has three size classes of dsRNAs: H (heavy), M (medium), and L (light). We find that, unique among dsRNA viruses, two segments of different size code for the same product--the toxin resistance factor. The smaller dsRNA (L) is homologous to one end of the larger (M), and may have arisen by replication and packaging of a sub-genomic mRNA. We have also compared all the UmV dsRNAs with each other and with the dsRNAs of the similar yeast virus (ScV) by Northern gel and by 3' sequence analysis. Like those of ScV, many of the UmV dsRNAs have one 3' terminus with the sequence UUUUUCAOH or UUUUUCGOH. The H and L dsRNAs of similar size in different viral subtypes are generally related in sequence. The UmV H dsRNAs of different size are not detectably related in sequence.

The mitochondrial genomes of Ustilago cynodontis and Acanthamoeba castellanii.

Mitochondrial DNA from Ustilago cynodontis has been investigated in several of its properties. Its dG + dC content is equal to 33.5%; its buoyant density (1.698 g/cm3) is higher, by 5 mg/cm3, and its melting temperature (82.5 degrees C) is lower than expected for a bacterial DNA having the same base composition; the first derivative of its melting curve indicates a large compositional heterogeneity, its molarity of elution from hydroxyapatite is high, 0.28 M phosphate, and allows its partial separation from nuclear DNA. Degradation by micrococcal nuclease indicates that about 25% of the DNA is formed by stretches having no more than 15% dG + dC. Finally, the unit size of mitochondrial genome is about 50 X 10(6). In most of its properties, the mitochondrial genome of U. cynodontis presents strong analogies with that of Saccharomyces cerevisiae. A parallel investigation on mitochondrial DNA from Acanthamoeba castellanii which has as genome unit size of only 27 X 10(6), has shown that this shares with the former the dG + dC content (32.9%), the melting temperature (82.5 degrees C), a large compositional heterogeneity and a very similar pattern of micrococcal nuclease degradation; its buoyant density (1.692 g/cm3) and its molarity of elution from hydroxyapatite (0.25 M phosphate) are, however, normal, probably because of a different short-sequence pattern and the fact that its dA + dT-rich stretches are shorter, on the average.

Further characterisation of a nucleic acid binding protein.

A glycoprotein which binds to nucleic acids has now been purified from Ustilago maydis until free from detectable deoxyribonuclease activity. It binds to a variety of substrates and in doing so, makes them soluble in dilute trichloroacetic acid. Physical studies suggest that it forms a variety of aggregates under low ionic strength, but at high ionic strength the monomer consists of a single polypeptide chain. Preliminary experiments have detected this novel binding activity in bacterial, fungal and mammalian cells.

Lipid composition of strains of the fungus Ustilago zeae (Beckm.) differing as regards their hybridization type.

The composition of the intracellular lipids was studied in four strains of Ustilago zeae differing as regards their hybridization type. In all strains, irrespective of the hybridization type, the bulk of the lipids are formed during the first three days of growth and constitute 43.2--55.7% of the weight of the dry cells. It was established that the total lipid fraction is composed of: phospholipids + monoglycerides, sterols, free fatty acids, diglycerides and sterol esters. The qualitative composition of the total lipids was found to be identical in all four strains regardless of the time of incubation of the cultures. While the qualitative composition remains constant, the ratio of the individual fractions changes in the various strains during the process of incubation. However, compatible strains with respect to hybridization do not differ as regards the amount of individual lipid fractions, while strains incompatible with respect to hybridization differ as regards this trait.

Inheritance of killer phenotypes and double-stranded RNA in Ustilago maydis.

Three different killer specificities in U. maydis are inherited cytoplasmically and transmitted by cell fusion. Each killer generates low frequencies of specifically immune forms in crosses with sensitive strains. The properties of immunity to each killer are also inherited cytoplasmically and transmitted by cell fusion. Killer strains carry virus-like particles about 41 nm in diameter. Each killer possesses distinct double-stranded RNA components that range in molecular weight from 0.46 X 10(6) to 2.9 X 10(6). Two components are shared by all three killers. Immune strains possess new forms. Crosses and heterokaryons between different killers revealed unilateral or mutual restrictions that prevent inclusion of two killer specificities in the same cell.