Hydride-mediated reduction of 2,4,6-trinitrotoluene by yeasts as the way to its deep degradation

Broad screening of microorganisms from natural and anthropogenic ecological niches has revealed strains Candida sp. AN-L15 and Geotrichum sp. AN-Z4 which transform, 2,4,6-trinitrotoluene (TNT) via alternative pathways (with the domination of hydride ion-mediated reduction of the aromatic ring) and produce relatively high amounts of nitrites. According to the spectrophotometry data, the hydride attack of TNT by Candida sp. AN-L15 and Geotrichum sp. AN-Z4 grown at pH 5.0–8.0 leads to the mono-and dihydride complexes of TNT (H^?-TNT and 2H^?-TNT, respectively) and to protonated forms of the latter. Analysis by HPLC, GC-mass spectrometry, and ion chromatography revealed the products of deep conversion of TNT. The growth of the yeast strains in a weakly acidic medium with TNT (440 μM) is accompanied by formation of 2,4-dinitrotoluene (2,4-DNT, up to 18.2 μM). Together with accumulation of nitrites (up to 76.0 μM, depending on pH of the medium), these findings demonstrate the capacity of both strains for TNT denitration. Formation of 2,4-DNT reflects the realization of one of the possible mechanisms of TNT ortho-nitro group elimination and switching over to the pathways of metabolism of dinitrotoluenes, which are much more easily biodegradable than TNT. Simultaneously with the dominating TNT hydride attack, the mechanism of 4-and 6-electron reduction of the nitro group also functions in Candida sp. AN-L15 and Geotrichum sp. AN-Z4. Realization of the studied mechanisms of TNT transformation under growth of Candida sp. AN-L15 on n-alkane is important for bioremediation in the cases of combined pollution by oil products and explosives.     

Hybrid Selection of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> Yeasts for Thermotolerance and Fermentation Activity

Molecular genetic screening of Saccharomyces yeasts, isolated from natural sources in the regions of the world with a hot climate (Africa, South America, Southeast and Central Asia) was used for the search of thermotolerant S. cerevisiae strains. Based on physiological tests, four strains were selected that could grow at high temperatures (42 and 43°C) and had good fermentation activity: 7962-4B, 3529-7B, 52922-4-1-1A- 1C, and 87-2421.1-2A. Hybrids of monosporic culture of distiller’s race XII (XII₇-2) with the thermotolerant strains were obtained. Unlike the strain XII₇-2, which is unable to grow at above 39°C, all hybrids showed good growth at 42°C. Two of the six hybrids analyzed, H2-1 (87-2421.1-2A × XII₇-2) and H3-2 (7962-4B × XII₇-2), showed higher fermentation activity than the parental strains. According to the results obtained, inter-strain hybridization is an efficient method of obtaining S. cerevisiae strains, which combine thermotolerance with high efficiency of alcoholic fermentation.     

Analysis of copia sequence variation within and between Drosophila species

The sequences of the 5' long-terminal repeat (LTR) and adjacent leader regions of 27 full-length copia elements isolated from natural populations of Drosophila melanogaster, D. simulans, and D. mauritiana are presented. Phylogenetic analyses indicate that although D. melanogaster copia elements are distinct from those of D. simulans and D. mauritiana, the elements of these latter two species are not distinguishable from one another. LTRs and adjacent 5' leader regions of elements isolated from D. simulans and D. mauritiana are structurally similar to one another and carry substantial deletional variation mapping to regions previously identified as being of potential importance for copia expression.      

The occurrence of teichoic acids in streptomycetes

The presence of teichoic acids in a number of streptomycetes led to the conclusion that these biopolymers were widely spread in genus Streptomyces. The nature of the teichoic acid present in the mycelium was determined by extracting it with 10% trichloroacetic acid, precipitating it with ethanol and identifying the precipitated polymer by partial acid and alkali hydrolysis to alditol, alditol phosphates and glycosylalditol phosphates. Most strains examined in this survey contained glycerol or ribitol teichoic acids; in some cases neither type was detected.Structurally teichoic acids closely resemble those of other genera of gram-positive bacteria and in many cases represent poly(glycerol phosphate) and poly(ribitol phosphate) chains. The proportion of alditol residues bearing sugar substituents varied widely.Three species of genus Streptoverticillium contained glycerol teichoic acids. It is belived that some of the data presented in this paper might be used with some success in taxonomic studies of streptomycetes.     

Characteristics of detection of the general direction of movement of visual objects by preschool-age children with typical and atypical cognitive development

The specifics of functioning of two channels for processing visual information, the magnocellular and parvocellular ones, in preschool children with normal and impaired cognitive development have been studied. Children with delayed psychological development have been found to have a diminished activity in the magnocellular channel due to weakening of the mechanism responsible for assessing the temporal parameters of the visual input. At the same time, children displaying a spectrum of infantile autism syndromes complicated by a delayed psychological development and mental retardation have a pronounced deficit in information processing in both channels of the visual system, manifested in an impaired ability to assess the direction of movement in terms of both temporal and spatial characteristics of the objects. The degree of this impairment is correlated with both the severity of the particular neurological disorder and the level of speech development of the child.     

Cell Wall Teichoic Acids of Two Brevibacterium Strains

Structurally identical teichoic acids were detected in cell walls of two soil isolates assigned to Brevibacterium linens based on phylogenetic data. Both cell walls contain unsubstituted 1,3-poly(glycerol phosphate) and poly(glycosylglycerol phosphate). Repeating units of the latter--alpha-D-GlcpNAc-(1-->4)-beta-D-Galp-(1-->1)-Gro--are bound by phosphodiester bonds including OH-3 of galactose and OH-3 of glycerol. Some of the N-acetylglucosamine residues have 4,6-pyruvic acid acetal, amounts of the latter in the two strains being unequal. Species-specificity of the structures of teichoic acids in the genus Brevibacterium is discussed.     

Nitrogen Requirements of Microtus rossiaemeridionalis

Total nitrogen requirements in the small herbivorous rodent Microtus rossiaemeridionaliswere studied. When provided with two kinds of standard laboratory food (about 20% and 0% digestible protein, respectively) ad libitum(cafeteria diet), the voles chose a diet of 14% protein. The total daily (with urine and faeces) nitrogen losses were, in this case, determined as 3.65 ± 0. 60 mg N/ g of body mass. When provided with a protein-free diet alone, the animals lost 0.90 ± 0,05 mg N/ g body mass per day, comprising about 3% of their body mass daily. It was proposed that the consumption of a low-fiber diet (about 4% in both kinds of food) could affect the gastrointestinal bacterial flora and, thus, lead to changes in the primarily herbivorous nitrogen metabolism.     

Mitochondrial DNA variability in populations and ethnic groups of Tatars of the Tobol-Irtysh basin

The data on mitochondrial DNA diversity in seven local populations (villages) and four territorial groups of Tatars of the Tobol-Irtysh basin are presented. In the Turkic-speaking populations from the Tobol and Irtysh river basins, high levels of intergroup and interpopulation mtDNA variation were observed. It was demonstrated that genetic diversity of the territorial groups of Tatars of the Tobol-Irtysh basin resulted from various interethnic relationships and different ethnic components integrated into these groups.