Study of the Protective Activity of Chitosan Hydrolyzate Against Septoria Leaf Blotch of Wheat and Brown Spot of Tobacco

Chitosan hydrolyzate containing low-molecular-weight chitosan (≤24 kDa) and its oligomers (≤1.2 kDa) has been obtained via chemical depolimerization of high-molecular-weight chitosan by nitric acid. The fractions of the obtained chitosan hydrolyzate have been characterized by high performance gel permeation chromatography and proton magnetic resonance. The test performed on detached leaves of wheat has shown that the hydrolyzate completely inhibits the development of Stagonospora nodorum, a casual agent of the septoria leaf blotch, at a concentration of 200 μg/mL. A similar test with detached tobacco leaves has shown that the hydrolyzate at a concentration of 100 μg/mL also inhibits the development of Alternaria longipes, which causes brown spot of tobacco, by 75%.     

Prediction of the three-dimensional structure of aflatoxin of Aspergillus flavus by homology modelling

Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus spp. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. AFLR-Protein three-dimensional model was generated using Robetta server. The modeled AFLR-Protein was further optimization and validation using Rampage. In the simulations, we monitored the backbone atoms and the C-α-helix of the modeled protein. The low RMSD and the simulation time indicate that, as expected, the 3D structural model of AFLR-protein represents a stable folding conformation. This study paves the way for generating computer molecular models for proteins whose crystal structures are not available and which would aid in detailed molecular mechanism of inhibition of aflatoxin.     

Strain Improvement of Streptomyces xanthochromogenes RIA 1098 for Enhanced Pravastatin Production at High Compactin Concentrations

Pravastatin is one of the most popular cholesterol-lowering drugs. Its industrial production represents a two-stage process including the microbial production of compactin and its further biocatalytic conversion to pravastatin. To increase a conversion rate, a higher compactin content in fermentation medium should be used; however, high compactin concentrations inhibit microbial growth. Therefore, the improvement of the compactin resistance of a producer still remains a relevant problem. A multi-step random UV mutagenesis of a Streptomyces xanthochromogenes strain RIA 1098 and the further selection of high-yield compactin-resistant mutants have resulted in a highly productive compactin-resistant strain S 33-1. After the fermentation medium improvement, the maximum bioconversion rate of this strain has reached 91 % at the daily compactin dose equal to 1 g/L and still remained high (83 %) even at the doubled dose (2 g/L). A 1-year study of the mutant strain stability has proved a stable inheritance of its characteristics that provides this strain to be very promising for the pravastatin-producing industry.

Electronic supplementary material

The online version of this article (doi:10.1007/s12088-015-0537-5) contains supplementary material, which is available to authorized users.     

Mapping the amino acid properties of constituent nucleoporins onto the yeast nuclear pore complex

Visualization of molecular structures aids in the understanding of structural and functional roles of biological macromolecules. Macromolecular transport between the cell nucleus and cytoplasm is facilitated by the nuclear pore complex (NPC). The ring structure of the NPC is large and contains several distinct proteins (nucleoporins) which function as a selective gate for the passage of certain molecules into and out of the nucleus. In this note we demonstrate the utility of a python code that allows direct mapping of the physiochemical properties of the constituent nucleoporins on the scaffold of the yeast NPC׳s cytoplasmic view. We expect this tool to be useful for researchers to visualize the NPC based on their physiochemical properties and how it alters when specific mutations are introduced in one or more of the nucleoporins. The code developed using Python is available freely from the authors.     

The Influence of Chemical Mutagenesis on the Properties of the Cyclosporine a High-Producer Strain <Emphasis Type="Italic">Tolypocladium inflatum</Emphasis> VKM F-3630D

The effects of treatment with the chemical mutagen N-nitroso-N-methylurea (NMU) on the survival rate, morphological variability, and the level of production of cyclosporine A (CyA) in the Tolypocladium inflatum subsporum blastosporum strain VKM F-3630D were studied. The range of exposure to the dose of the mutagen (incubation time and concentration of HMU) was determined. The lethal and sublethal doses, as well as the conditions under which the highest variability in the levels of CyA production was observed, were determined. It was shown that the most efficient method to further increase CyA production in the studied high-producer T. inflatum strain is mutagenic treatment with 0.1% HMU for 2 h. In this case, we observed a relatively high level of survival of clones (80–85%), a low level of their morphological variability (10–15%), and a wide range in the CyA production level (80–170%) as compared to the original strain. This enabled us to select a number of clones with an increased CyA production level. The yield of the target metabolite was maximal in clone no. 13-27, where the CyA production level increased by 1.6–1.7 times.     

Complete mitochondrial genome of compactin-producing fungus Penicillium solitum and comparative analysis of Trichocomaceae mitochondrial genomes

We determined the complete mitochondrial genome sequence of the compactin-producing fungus Penicillium solitum strain 20-01. The 28?601-base pair circular-mapping DNA molecule encodes a characteristic set of mitochondrial proteins and RNA genes and is intron-free. All 46 protein- and RNA-encoding genes are located on one strand and apparently transcribed in one direction. Comparative analysis of this mtDNA and previously sequenced but unannotated mitochondrial genomes of several medically and industrially important species of the Aspergillus/Penicillium group revealed their extensive similarity in terms of size, gene content and sequence, which is also reflected in the almost perfect conservation of mitochondrial gene order in Penicillium and Aspergillus. Phylogenetic analysis based on concatenated mitochondrial protein sequences confirmed the monophyletic origin of Eurotiomycetes.