Involvement of Azopirillum brasilense plasmid DNA in the productio of indole acetic acid

Indole acetic acid (IAA) production in Azospirillum brasilense strain Sp245 is controlled by a 85 MDa plasmid naturally present in this bacterium. In the presence of L-tryptophan, anthranilic acid production and almost no IAA production occurs in a derivative strain harbouring a Tn5-Mob insertion in the 85 MDa plasmid. Agrobacterium tumefaciens strain GM19023, upon transfer of Tn5-Mob labelled 85 MDa plasmid of A. brasilense Sp245, gains the ability to produce anthranilic acid.     

Yersinia pseudotuberculosis plasmids and their significance in the realization of the epidemic process in pseudotuberculosis

The results obtained in the electrophoretic study of the plasmid spectra of 190 Y. pseudotuberculosis strains, isolated from different sources, in 0.6% agarose gel are presented. 11 types of plasmids differing in their molecular weight have been detected. Plasmids with a molecular weight of 45 MD determine Ca2+ dependence, bacterial virulence for white mice and autoagglutination. The presence of differences in Y. pseudotuberculosis strains of serovars I, III and IV has been established, which is manifested by their differing plasmid spectra. The relationship between the presence of plasmids with a molecular weight of 75 and 45 DM in the strains and the character of pseudotuberculosis morbidity in the population has been demonstrated. The epidemic course of infection correlates with the presence of both these plasmids and the sporadic course of infection, with the presence of the plasmid with a molecular weight of 45 MD only.     

Polysaccharide-Degrading Activity in Marine and Terrestrial Strains of Mycelial Fungi

The activity of extracellular polysaccharide-degrading enzymes and glycosidases from mycelial fungi towards various carbohydrates and carbohydrate derivatives from plant and algal cell walls has been screened. Twenty-three strains of mycelial fungi isolated from the marine sediment and dung were grown by submerged cultivation on a plant-based substrate (a by-product of the grain processing industry) for previous screening for their biomass and protein productivity. Molecular identification allowed for the assignment of marine fungal strains to the following species: Sirastachys phyllophila, Ochroconis mirabilis, Pseudallescheria boydii, Pseudallescheria ellipsoidea, Beauveria felina, Scopulariopsis brevicaulis, Cladosporium sp., and Trichoderma sp. The terrestrial strains belonged to the species Thermomyces thermophilus, Thermomyces dupontii, Thermomyces lanuginosus, Fusarium avenaceum, Mycothermus thermophilum, and Thermothelomyces thermophila. Seven strains of thermophilic terrestrial fungal species T. thermophila, T. thermophilus, T. dupontii and M. thermophilus and two marine fungal strains of S. brevicaulis and Beauveria felina exhibited the highest protein yields and a wide range of polysaccharide-degrading activity when the cultures were cultivated at 22–25°C. The cellulolytic thermophilic strain M. thermophilus 55 isolated from dung demonstrated unusual specificity, most intensive increase of mycelial biomass, and high activity towards algal polysaccharides after seven days of cultivation. The specific activity of laminarinase was one order of magnitude higher than in the marine strains and amounted to 1180 U/mg, and the alginate lyase, carrageenase, polymannuronate lyase, agarase, and fucoidanase activity levels (from 208 to 500 U/mg) were also higher than in all marine strains. All active polysaccharide-degrading strains of thermophilic terrestrial and marine fungi identified in the present study are of considerable interest, as the potential of these fungi for polysaccharide degradation can be applied in the transformation of various agricultural and maricultural waste of plant origin and in the modification of carbohydrate-containing substances in structural research and biotechnology.     

Controlling the near‐infrared transparency of costal cartilage by impregnation with clearing agents and magnetite nanoparticles

Penetration depth of near‐infrared laser radiation to costal cartilage is controlled by the tissue absorption and scattering, and it is the critical parameter to provide the relaxation of mechanical stress throughout the whole thickness of cartilage implant. To enhance the penetration for the laser radiation on 1.56 μm, the optical clearing solutions of glycerol and fructose of various concentrations are tested. The effective and reversible tissue clearance was achieved. However, the increasing absorption of radiation should be concerned: 5°C‐8°C increase of tissue temperature was detected. Laser parameters used for stress relaxation in cartilage should be optimized when applying optical clearing agents. To concentrate the absorption in the superficial tissue layers, magnetite nanoparticle (NP) dispersions with the mean size 95 ± 5 nm and concentration 3.9 ± 1.1 × 10¹¹ particles/mL are applied. The significant increase in the tissue heating rate was observed along with the decrease in its transparency. Using NPs the respective laser power can be decreased, allowing us to obtain the working temperature locally with reduced thermal effect on the surrounding tissue.      

Structure of the carboxypeptidase B complex with N-sulfamoyl-L-phenylalanine – a transition state analog of non-specific substrate

Carboxypeptidase B (EC 3.4.17.2) (CPB) is commonly used in the industrial insulin production and as a template for drug design. However, its ability to discriminate substrates with hydrophobic, hydrophilic, and charged side chains is not well understood. We report structure of CPB complex with a transition state analog N-sulfamoyl-L-phenylalanine solved at 1.74Å. The study provided an insight into structural basis of CPB substrate specificity. Ligand binding is affected by structure-depended conformational changes of Asp255 in S1’-subsite, interactions with Asn144 and Arg145 in C-terminal binding subsite, and Glu270 in the catalytic center. Side chain of the non-specific substrate analog SPhe in comparison with that of specific substrate analog SArg (reported earlier) not only loses favorable electrostatic interactions and two hydrogen bonds with Asp255 and three fixed water molecules, but is forced to be in the unfavorable hydrophilic environment. Thus, Ser207, Gly253, Tyr248, and Asp255 residues play major role in the substrate recognition by S1’-subsite.     

Vibrational CD (VCD) and atomic force microscopy (AFM) study of DNA interaction with Cr3+ ions: VCD and AFM evidence of DNA condensation

The interaction of natural calf thymus DNA with Cr³⁺ ions was studied at room temperature by means of vibrational CD (VCD) and infrared absorption (ir) spectroscopy, and atomic force microscopy (AFM). Cr³⁺ ion binding mainly to N₇ (G) and to phosphate groups was demonstrated. ψ‐Type VCD spectra resembling electronic CD (ECD) spectra, which appear during ψ‐type DNA condensation, were observed. These spectra are characterized mainly by an anomalous, severalfold increase of VCD intensity. Such anomalous VCD spectra were assigned to DNA condensation with formation of large and dense particles of a size comparable to the wavelength of the probing ir beam and possessing large‐scale helicity. Atomic force microscopy confirmed DNA condensation by Cr³⁺ ions and the formation of tight DNA particles responsible for the ψ‐type VCD spectra. Upon increasing the Cr³⁺ ion concentration the shape of the condensates changed from loose flower‐like structures to highly packed dense spheres. No DNA denaturation was seen even at the highest concentration of Cr³⁺ ions studied. The secondary structure of DNA remained in a B‐form before and after the condensation. VCD and ir as well as AFM proved to be an effective combination for investigating DNA condensation. In addition to the ability of VCD to determine DNA condensation, VCD and ir can in the same experiment provide unambiguous information about the secondary structure of DNA contained in the condensed particles. © 2002 Wiley Periodicals, Inc. Biopolymers 61: 243–260, 2002