Phytotoxic Activities of Chernozem Saprotrophic Micromycetes: Specificity,Sorption, and Stability of Phytotoxins in Soil

Micromycetes of the complex of typical chernozem saprotrophic fungi released phytotoxic metabolites into their growth medium. The metabolites displayed their phytotoxic activities directly in soil. Evaluation of the toxicity, range of biological effects, activity, and stability of the phytotoxins in soil, as well as of the rates of their biodegradation, made it possible to select species that can serve as indicators of microbial toxicosis of chernozem (Aspergillus clavatus, Fusarium solani, Talaromyces flavus, Penicillium rubrum, and P. funiculosum).     

Clinical and microbiological features of acute enteric mixed infection caused by Hafnia alvei and rotavirus

The data obtained in the clinical and laboratory study of 72 hospitalized patients with acute enteric infection are presented. The observed outbreak was caused by H. alvei producing heat-stable enterotoxin. The role of this etiological agent is also confirmed by simultaneous occurrence of the disease after using the same foodstuff, a short incubation period, the severity of the course of the disease with pronounced symptoms of neurotoxicosis, a high detection rate of H. alvei in material taken from patients at the acute period of the disease, rapid disappearance of this agent in the period of convalescence and a pronounced rise in the titer of specific antibodies to H. alvei in the dynamics of the disease. At the same time in the feces of 8 patients rotavirus antigen was detected, which, in combination with residual catarrhal phenomena, hyperemia and granularity of the pharynx, yellow stool, was indicative of the simultaneous circulation of rotavirus among these patients.     

The properties of the cellular surface of Yersinia pestis strain EV and its achromogenic variants

The comparative study of the properties of the surface of vaccine strain Y. pestis EV and its achromogenic variants (AV) differing from the initial strain by decreased immunogenicity and by the morphology of colonies, has been made. The achromogenicity of Y. pestis colonies has been shown to correlate with the loss of the outer membrane protein with a molecular weight 22 kD. The synthesis of this protein is determined by chromosomal genes. AV have been found to have different sensitivity to bacteriophages. The analysis of the electrokinetic potential of Y. pestis EV and its AV has revealed that in the latter have surface charge is considerably greater (1.4- to 1.5-fold). As shown in this study, the hemagglutinating activity of AV with respect to red blood cells of humans with blood group I (O) and guinea pigs is decreased by 1-2 orders and these strains do not agglutinate with sheep red blood cells. The low activity of the initial stage of the phagocytosis of AV by mouse macrophages has been shown. The possible role of the 22 kD proteins as an adhesion factor is discussed.     

Recombinant non-structural 3A, 3B and 3AB proteins of foot-and-mouth disease virus: use for differentiation of vaccinated and infected cattle

Recombinant proteins 3A, 3B and 3AB were obtained by expression in Escherichia coli and purified by metal-chelate chromatography. The proteins were used as antigens in indirect ELISA to differentiate vaccinated and infected cattle. While testing 200 sera from cattle 3A-ELISA was more sensitive and specific than 3B- and 3AB-ELISA. Compared with "Chekit FMD-3ABC", 3A-ELISA showed the same level of specificity and higher level of sensitivity.     

Role of nitrogen metabolism in the development of salt tolerance in barley plants

The 7- to 8-day-old barley (Hordeum vulgare L.) seedlings grown in KNO3 solutions (1-40 mM) were characterized by the substrate activation of nitrate reductase (NR) in the apical leaf segments (1–2 cm in length), as well as by stimulated growth, broadened leaf blades, and by vigorously developed system of shortened roots. When the seedlings were grown in the presence of 20 mM KNO₃, the ability of leaf segments to generate superoxide anion radical remained at the level typical of control plants grown in water. The content of 5-aminolevulinic acid (ALA) in plants grown in the presence of 20 mM KNO₃ was 2.2–2.4 times higher than in control plants. The plants grown in the presence of nitrate had an elevated content of chlorophylls a and b, heme, and protein (by 42%). At the same time, the proline content was almost twofold lower than in control plants, which was due to substantial reduction (by 40%) in activity of Δ¹-pyrroline-5-carboxylate synthetase (P5CS). It is concluded that the substrate activation of NR by KNO₃ under normal growth conditions results in predominant utilization of glutamic acid (the primary product of inorganic nitrogen assimilation) for biosynthesis of tetrapyrroles and protein amino acids at the expense of inhibition of proline synthesis. When barley seedlings were grown in 150 mM NaCl solution, the plant growth and the root system development were suppressed to the levels of 63 ± 6% and 61 ± 11% of the control values, respectively. In the apical leaf tissues of plants adapted to NaCl, there was a slight decrease in the total NR activity (by 10%), a significant reduction in protein content (by 32%), and a parallel increase in the content of ALA (by a factor of 4.3), chlorophylls, heme, carotenoids, proline (2.2-fold) and P5CS (1.6-fold) with respect to the control values. It is proposed that the accumulation of ALA and proline under salinity-induced suppression of nitrogen assimilation results from the predominant allocation of glutamate for biosyntheses of ALA and proline at the expense of inhibition of growth-related processes requiring intense protein synthesis. The substrate activation of NR by KNO₃ under salinity conditions was associated with prevailing allocation of the assimilated nitrogen for synthesis of proline and protein amino acids, which reinforced plant cell protection against salinity and stimulated plant growth.     

Double-strand break repair and recombination-dependent replication of DNA in bacteriophage T4 in the absence of UvsX recombinase: replicative resolution pathway

The effects of mutations in bacteriophage T4 genes uvsX and 49 on the double-strand break (DSB)-promoted recombination were studied in crosses, in which DSBs were induced site-specifically within the rIIB gene by SegC endonuclease in the DNA of only one of the parents. Frequency of rII+ recombinants was measured in two-factor crosses of the type i×ets1 and in three-factor crosses of the type i×ets1 a6, where ets1 is an insertion in the rIIB gene carrying the cleavage site for SegC; i's are rIIB or rIIA point mutations located at various distances (12-2040 bp) from the ets1 site, and a6 is rIIA point mutation located at 2040 bp from ets1. The frequency/distance relationships were obtained in crosses of the wild-type phage and of the amber mutant S17 (gene uvsX) and the double mutant S17 E727 (genes uvsX and 49). These data provide information about the frequency and distance distribution of the single-exchange (splices) and double-exchange (patches) events. The extended variant of the splice/patch coupling (SPC) model of recombination, which includes transition to the replication resolution (RR) alternative is substantiated and used for interpretation of the frequency/distance relationships. We conclude that the uvsX mutant executes recombination-dependent replication but does it by a qualitatively different way. In the absence of UvsX function, the DSB repair runs largely through the RR subpathway because of inability of the mutant to form a Holliday junction. In the two-factor crosses, the double uvsX 49- is recombinationally more proficient than the single uvsX mutant (partial suppression of the uvsX deficiency), while the patch-related double exchanges are virtually eliminated in this background.     

Double-strand break repair in bacteriophage T4: recombination effects of 3'-5' exonuclease mutations

The role of 3'-5' exonucleases in double-strand break (DSB)-promoted recombination was studied in crosses of bacteriophage T4, in which DSBs were induced site specifically within the rIIB gene by SegC endonuclease in the DNA of only one of the parents. Frequency of rII+ recombinants was measured in two-factor crosses of the type i x ets1, where ets1 designates an insertion in the rIIB gene carrying the cleavage site for SegC and i's are rIIB or rIIA point mutations located at various distances (12-2040 bp) from the ets1 site. The frequency/distance relationship was obtained in crosses of the wild-type phage and dexA1 (deficiency in deoxyribonuclease A), D219A (deficiency in the proofreading exonuclease of DNA polymerase), and tsL42 (antimutator allele of DNA polymerase) mutants. In all the mutants, recombinant frequency in crosses with the i-markers located at 12 and 33 bp from ets1 was significantly enhanced, implying better preservation of 3'-terminal sequences at the ends of the broken DNA. The effects of dexA1 and D219A were additive, suggesting an independent action of the corresponding nucleases in the DSB repair pathway. The recombination enhancement in the dexA1 mutant was limited to short distances (<100 bp from ets1), whereas in the D219A mutant a significant enhancement was seen at all the tested distances. From the character of the frequency/distance relationship, it is inferred that the synthesis-dependent strand-annealing pathway may operate in the D219A mutant. The recombination-enhancing effect of the tsL42 mutation could be explained by the hypothesis that the antimutator 43Exo removes a shorter stretch of paired nucleotides than the wild-type enzyme does during hydrolysis of the unpaired terminus in the D-loop intermediate. The role of the proofreading exonuclease in the formation of a robust replicative fork is discussed.     

Genetic recombination: Formal implications of a crossed strand-exchange between two homologous DNA molecules

Formal genetic consequences of generation and break-up of a structure with cross connection have been studied on the basis of a simple quantitative model with a symmetric exchange of two strands between parental DNA molecules. In recombination analysis, this intermediate structure gives rise to a critical frequency R(ξ) (see Fig. 3), which corresponds to recombination between two markers separated by a distance equal to the mean genetic length ξ of the hybrid region at the time of scission of the cross connection. As concerns the routine mapping practice, a fundamental inference emerges: since genetic exchange has no invariable equivalent on molecular level it fails basically to serve as statistically independent elementary event in fine scale mapping. Instead of the number of exchanges between markers (or proportional metrics) the use of the number of the sites of initiation of hybrid regions (or proportional metrics) as a measure of map distance is suggested. Usage of the mean length of hybrid region ξ as a natural unit of map distance is shown to be of particular interest.In the case of bacteriophage T4 under the conditions of standard crosses, the structure with cross connection is characterized by the value R(ξ) equal to 3·0.10^?2, at the time of scission of the cross connection this structure acquiring either of the two alternative isomeric configurations with equal probability. About four percent of the total number of mismatches emerging as a result of formation of hybrid regions were repaired.     

Immune Checkpoints of the B7 Family. Part 2. Representatives of the B7 Family B7-H3, B7-H4, B7-H5, B7-H6, B7-H7, and ILDR2 and Their Receptors

Russian Journal of Bioorganic Chemistry - Immune checkpoints regulate polarity, strength, and termination of the immune response. The leading roles in these processes are played by molecules of the...