卤虫染色体倍性组成的研究

本文报道了我国4个地理品系卤虫的染色体倍性组成及卵径分布,分析了卤虫染色体的非整倍性,讨论了卤虫种的分布。 天津卤虫有2倍体(2n=42),占33.3％和5倍体,占16.2％;染色体数的波动为21—108;卵径为262±17μm。 海南卤虫有2倍体(2n=42),占8％;4倍体,占17.7％;5倍体,占18.3％;染色体数的波动为16—111;卵径为285±15μm。 新疆卤虫有2倍体(2n=42),占39.2％;染色体数的波动为17—106;卵径为269±15μm。 山西卤虫有2倍体(2n=42),占45.1％,染色体数的波动为17—84;卵径为234±13μm。     

A型肉毒毒素轻链基因的克隆及其结构分析

以献报道的A型肉毒毒素基因全序列为标准,设计并合成一对引物,自肉毒梭菌基因组中扩增出肉毒毒素轻链基因片段,并将扩增产物与pGEM—T载体在体外连接,构建测序重组质粒,进行测序和基因结构分析。PCR扩增获得了产物为1 364bp的DNA片段,测序结果与DNA数据库对照检索分析证明,此基因片段与GenBank中的A型肉毒毒素LC基因的一致性达99．9％以上,可以认为克隆的基因为A型肉毒毒素LC基因。     

Microbial processes at the Lost City vent field,Mid-Atlantic Ridge

Microbiological and biogeochemical measurements showed that the intensities of CO₂ assimilation, methane oxidation, and sulfate reduction at the Lost City vent field (3° N) reach 3.8 µg C/(1 day), 0.06 µg C/(1 day), and 117 µg S/(1 day), respectively. On the surface of the carbonate structures occurring at this field, two varieties of bacterial mats were found. The first variety, which is specific to the Lost City alkaline vent field, represents jellylike bacterial mats dominated by slime-producing bacteria of several morphotypes. This mat variety also contains chemolithotrophic and heterotrophic microorganisms, either microaerobic or anaerobic. The intensities of CO₂ assimilation, methane oxidation, and sulfate reduction in this variety reach 747 µg C/(dm³ day), 0.02 µg C/(dm³ day), and 28000 µg S/(dm³ day), respectively. Bacterial mats of the second variety are formed by nonpigmented filamentous sulfur bacteria, which are close morphologically to Thiothrix. The intensities of CO₂ assimilation, methane oxidation, and sulfate reduction in the second mat variety reach 8.2 µg C/(dm³ day), 5.8 µg C/(dm³ day), and 17000 µg S/(dm³ day), respectively. These data suggest the existence of subsurface microflora at the Lost City vent field.Translated from Mikrobiologiya, Vol. 74, No. 1, 2005, pp. 111–118.Original Russian Text Copyright © 2005 by Dulov, Lein, Dubinina, Pimenov.     

The functional role of reduced inorganic sulfur compounds in the metabolism of the microaerophilic bacterium <Emphasis Type=Italic>Spirillum winogradskii</Emphasis>

Oxidation of reduced sulfur compounds by the microaerophilic sulfur bacterium spirillum winogradskii was found to occur only concomitantly with consumption of an organic substrate and was not linked to their utilization as electron donors in energy metabolism. No enzymes of dissimilatory sulfur metabolism were found in the cells of the sulfur bacterium oxidizing thiosulfate to tetrathionate; oxidation of thiosulfate and sulfide was caused by their reaction with reactive oxygen species (ROSs), mostly H₂O₂ produced in the course of aerobic growth. A decreased lytic effect of ROSs in the presence of thiosulfate resulted in a twofold increase in the cell yield under aerobic conditions and more efficient substrate utilization. The latter effect was caused by decreased expenditure of energy for the biosynthesis of oxygen-protective polysaccharides. The stimulatory effect of thiosulfate on the growth processes was due to the activation of a number of TCA cycle enzymes producing the intermediates for constructive metabolism, especially of the NADP-dependent malic enzyme. As a result of thiosulfate-induced synthesis of SH-containing cell components, the integral antioxidative activity increased 1.5-fold.Translated from Mikrobiologiya, Vol. 74, No. 1, 2005, pp. 17–25.Original Russian Text Copyright © 2005 by Podkopaeva, Grabovich, Dubinina.     

Some aspects of avian flu in the Tyumen region

The list of the actions spent in the summer of 2005 in territory of the Tyumen region, in connection with a destruction of wild birds and poultry from the avian flu is submitted. Except for the quarantine and other sanitary-epidemic measures warning drift of a avian influenza virus in facilities, it is carried out of serological monitoring among workers of poultry-farming facilities and the population of the struck settlements on presence of antibodies to an influenza A (H5N1) virus. Taking into account ways of migration of a wild waterfowl in this territory, probability of contact to it and risk of infection of people, the conclusion about necessity of continuation the monitoring behind circulation of an avian influenza virus in region is made.     

Arthrobacter siderocapsulatus isolated from lake water]

Two microbial strains have been isolated from lake water. The strains oxidize ferrous compounds and manganese. By the structure of microcolonies and the character of deposited oxides of these metals, the strains are identical to the genus Siderocapsa. However, according to their growth cycle and some morpho-physiological characteristics, they were included into the genus Arthrobacter (Corynebacteriaceae). Since these microorganisms differ, by their cultural and morpho-physiological properties, from other species of this genus, they were classed as a new species. Arthrobacter siderocapsulatus nov. sp.     

Morphophysiological monitoring of winter wheat in spring in the context of global climate warming

Data on morphophysiological monitoring of winter wheat (Triticum aestivum L.) cultivar Mironovskaya 808 grown in Hoagland and Arnon solution in a greenhouse and transferred to natural conditions in March–April 2004 with the mean daily temperature of 0.6 ± 0.7°C within the exposure period of 42 days are presented. Water content, dry weight of plants and their organs, frost hardiness of plants, degree of tissue damage by frost, CO₂ metabolism (photosynthesis and respiration), concentrations of sugars in tissues and proportions between different sugar forms, and activities of soluble and insoluble acid and alkaline phosphatases were monitored. Monitoring was carried out for three experimental variants simulating different microclimatic conditions in spring: after snow melting (experiment I), under ice crust (experiment II), and under snow cover (experiment III). Plants in experiments III and II demonstrated a higher water content in tissues, lower frost hardiness, higher rates of biomass loss, lower concentration of sugars and lower di-to monosaccharide ratio in tissues, and higher total invertase activity, particularly, cell wall-associated acid invertase activity. The dark respiration rates at 0°C did not significantly differ between experimental variants. The photosynthetic capacity at this measurement temperature was maintained in all experimental variants being most pronounced in experiment II with the most intense photoinhibition under natural conditions. Comparison of experiments III and II with experiment I is used to discuss the negative effect of changes in certain microclimatic indices associated with global warming and leading to plant exhaustion and death from frost in spring.     

Lithotrophic microorganisms of the oxidative cycles of sulfur and iron

The review deals with sulfur bacteria (the first chemolithotrophs ever studied) and with the acidophilic bacteria of sulfur and iron cycles which were investigated as a result of Winogradsky’s discovery. The diversity of these organisms and the factors and mechanism of its origin are emphasized; their metabolic functions and nutritional regulation are discussed.     

L-citrulline supplementation reverses the impaired airway relaxation in neonatal rats exposed to hyperoxia

Background

Hyperoxia is shown to impair airway relaxation via limiting L-arginine bioavailability to nitric oxide synthase (NOS) and reducing NO production as a consequence. L-arginine can also be synthesized by L-citrulline recycling. The role of L-citrulline supplementation was investigated in the reversing of hyperoxia-induced impaired relaxation of rat tracheal smooth muscle (TSM).

Methods

Electrical field stimulation (EFS, 2–20 V)-induced relaxation was measured under in vitro conditions in preconstricted tracheal preparations obtained from 12 day old rat pups exposed to room air or hyperoxia (>95% oxygen) for 7 days supplemented with L-citrulline or saline (in vitro or in vivo). The role of the L-citrulline/L-arginine cycle under basal conditions was studied by incubation of preparations in the presence of argininosuccinate synthase (ASS) inhibitor [α-methyl-D, L-aspartate, 1 mM] or argininosuccinate lyase inhibitor (ASL) succinate (1 mM) and/or NOS inhibitor [N^ω-nitro-L-arginine methyl ester; 100 μM] with respect to the presence or absence of L-citrulline (2 mM).

Results

Hyperoxia impaired the EFS-induced relaxation of TSM as compared to room air control (p < 0.001; 0.5 ± 0.1% at 2 V to 50.6 ± 5.7% at 20 V in hyperoxic group: 0.7 ± 0.2 at 2 V to 80.0 ± 5.6% at 20 V in room air group). Inhibition of ASS or ASL, and L-citrulline supplementation did not affect relaxation responses under basal conditions. However, inhibition of NOS significantly reduced relaxation responses (p < 0.001), which were restored to control level by L-citrulline. L-citrulline supplementation in vivo and in vitro also reversed the hyperoxia-impaired relaxation. The differences were significant (p <0.001; 0.8 ± 0.3% at 2 V to 47.1 ± 4.1% at 20 V without L-citrulline; 0.9 ± 0.3% at 2 V to 68.2 ± 4.8% at 20 V with L-citrulline). Inhibition of ASS or ASL prevented this effect of L-citrulline.

Conclusion

The results indicate the presence of an L-citrulline/L-arginine cycle in the airways of rat pups. L-citrulline recycling does not play a major role under basal conditions in airways, but it has an important role under conditions of substrate limitations to NOS as a source of L-arginine, and L-citrulline supplementation reverses the impaired relaxation of airways under hyperoxic conditions.