A lipopolysaccharide fromAspergillus flavus conidia

A lipopolysaccharide was isolated by extraction ofAspergillus flavus conidia with 45 % phenol at 68–70 °C. Quantitative analysis revealed 7 % nucleic acids, 5.5 % proteins, 46 % polysaccharides and 49 % lipids, of which 12 % were covalently bound. Glucose, mannose, galactose and fucose were detected as monosaccharide components of the polysaccharide moiety by gas chromatography; palmitic acid, stearic acid, oleic acid, linoleic acid and myristic acid were mainly present in the lipidic fraction. This material differs from the bacterial lipopolysaccharides, both in composition of the polysaccharide moiety and representation of fatty acids in the lipidic fraction.     

Variability ofAspergillus niger after treatment withN-methyl-N′-nitro-N-nitrosoguanidine

N-Methyl-N'-nitro-N-nitrosoguanidine influences strongly the variability of Aspergillus niger MU 90, particularly on long-term treatment. The number of spores capable of growth decreases with the duration of treatment and the number of morphological and biochemical mutants considerably increases. The highest number of mutants with increased organic acid production was obtained after a mutagenic treatment when the number of surviving spores decreased below 1%.     

Uptake of microperoxidase by segmenting rat ova in vitro

Summary Uptake and incidence of microperoxidase (Sigma) in the rat ova during cleavage at the 1-, 2-, 8-cell and blastocyst stages were studied after 30 min incubation with the enzyme (molecular weight of 1,900 and size of molecule of 2 nm).Evidence was furnished of the presence of a small amount of reaction product of microperoxidase in the zona pellucida and its local concentration in some parts of the perivitelline space. The larger part of surface of the ovum, however, was free of microperoxidase. In the cytoplasm microperoxidase was found in pinocytotic vesicles, less frequently in large vacuoles and starting with the eight-cell stage in secondary lysosomes. The largest amount of microperoxidase was ascertained at the stage of blastocyst, chiefly in the cells of the trophoblast. In the cells of the embryoblast, on the contrary, microperoxidase was found but occasionally. The reaction product of microperoxidase was also present in the intercellular space of ova in negligible amount, and likewise on the side of blastocysts' cavity. In comparison with the ingestion of horseradish peroxidase the incidence of microperoxidase in the segmenting rat ova was less frequent.     

Origin of sclerotia-like cells in submerged Claviceps purpurea producing clavine alkaloids

Ultrathin sectioning of submerged mycelium of Claviceps purpurea Tul. producing clavine alkaloids revealed yeast-like budding resulting in asexual sporesblastospores. These deciduous spores were born by extended hyphal cells and retained the same ultrastructure of cell organelles. Both the extended hyphae and the blastospores resembled the cells of ergot sclerotial tissue. A surface culture of C. purpurea Tul. producing no alkaloids was used as a reference.     

The effect of splenectomy, produced chemically by means of ethylpalmitate, on the formation of heteroagglutinins in the rat]

The formation of heteroagglutinins against human O-erythrocytes was pursued in Wistar rats splenectomized "chemically" by means of intravenous injections of ethyl palmitite. Contrary to some data in literature the initial inhibition in the formation of antibodies was replaced by a significant titre increase ranging from the 8th to the 14th day following immunization. The tween 20 contained in the emulsion of ethyl palmitic did not influence the formation of heteroagglutinins. The examinations show that a possible use of palmitic ethyl for immunosuppression is questionable.     

Penicillinamidohydrolase inEscherichia coli

Substrate specificity of the bacterial penicillinamidohydrolase (penicillinacylase, EC 3.5.1.11) fromEscherichia coli was determined by measuring initial rates of enzyme hydrolysis of different substrates within zero order kinetics. SomeN-phenylacetyl derivatives of amino acids and amides of phenylacetic acid and phenoxyacetic acid of different substituted amides of these acids or amides, structurally and chemically similar to these compounds, served as substrates. Significant differences in ratios of initial Tates of the enzyme hydrolysis of different substrates were found when using a toluenized suspension of bacterial cells or a crude enzyme preparation, in spite of the fact that the enzyme is localized between the cell wall and cytoplasmic membrane, in the so-called periplasmic space.N-phenylacetyl derivatives are the most rapidly hydrolyzed substrates. Beta-phenylpropionamide and 4-phenylbutyramide were not utilized as substrates. The substrate specificity of the enzyme is discussed with respect to a possible use of certain colourless compounds as substrates, hydrolysis of which yields chromophor products suitable for a simple and rapid assay of the enzyme activity.     

The topology of genome-scale metabolic reconstructions unravels independent modules and high network flexibility

The topology of metabolic networks is recognisably modular with modules weakly connected apart from sharing a pool of currency metabolites. Here, we defined modules as sets of reversible reactions isolated from the rest of metabolism by irreversible reactions except for the exchange of currency metabolites. Our approach identifies topologically independent modules under specific conditions associated with different metabolic functions. As case studies, the E.coli iJO1366 and Human Recon 2.2 genome-scale metabolic models were split in 103 and 321 modules respectively, displaying significant correlation patterns in expression data. Finally, we addressed a fundamental question about the metabolic flexibility conferred by reversible reactions: “Of all Directed Topologies (DTs) defined by fixing directions to all reversible reactions, how many are capable of carrying flux through all reactions?”. Enumeration of the DTs for iJO1366 model was performed using an efficient depth-first search algorithm, rejecting infeasible DTs based on mass-imbalanced and loopy flux patterns. We found the direction of 79% of reversible reactions must be defined before all directions in the network can be fixed, granting a high degree of flexibility.     

Permeabilization and lysis induced by bacteriocins and its effect on aldehyde formation by Lactococcus lactis

Permeabilization induced by lacticin 3147, lactococcins A, B and M, enterocin AS-48 and nisin, bacteriocins described as cell membrane-pore forming and lytic agents, enhanced in all cases aldehyde formation by Lactococcus lactis IFPL730. Nevertheless, the conversion of isoleucine into 2-methylbutyraldehyde depended not only on the degree of permeabilization but also on the bacteriocin that caused the cell membrane damage. The highest values of 2-methylbutyraldehyde corresponded to cell suspensions containing lacticin 3147 and lactococcins, treatments that provoked further lysis in addition to induced permeabilization.