The life strategy and self-regulation mechanisms of populations of the causative agents of sapronoses (exemplified by Pseudomonas pseudomallei)

The strategy of the selection (life) of P. pseudomallei has been defined as C-competitiveness, combining the advantages of the limited (r and K) types of the ecological strategies of microorganisms and ensuring their good capacity of survival in soil biota. The self-regulation mechanisms of P. pseudomallei populations in the environment are determined by the type of their strategy of selection, which also determines the place of this species among other organisms inhabiting the soil. C-competitiveness of P. pseudomallei permits the realization of the self-support of its populations under changing conditions of their habitat, in particular in vivo.     

Taste attractiveness of free amino acids and their physicochemical and biological properties (as exemplified by fishes)

Using fishes (32 species, 11 families) as an example, the relationship between the taste attractiveness of free amino acids (L-isomers) and their physicochemical and biological properties was analyzed. It was shown that essential amino acids, most nutritionally required for an organism, have lower taste attractiveness for fishes than nonessential amino acids. Only in 6 of the 32 tested species (sunbleak Leucaspius delineatus, European minnow Phoxinus phoxinus, dace Leuciscus leuciscus, chub Leuciscus cephalus, blue gourami Trichopodus trichopterus, pearl gourami Trichopodus leerii) the relationship between the taste attractiveness and molecular weight of amino acids was supported statistically, being negative in all cases. Only in 2 species, a statistically significant correlation between the taste properties of amino acids and the dissociation constant (K₁) was found, positive in the stone loach Barbatula barbatula and negative in the lake char Salvelinus namaycush. A positive correlation between taste preferences and the magnitude of the isoelectric point (pI) of amino acids was found in one species (roach Rutilus rutilus) and a negative correlation in 2 species (brown trout Salmo trutta and Arctic char Salvelinus alpinus erythrinus). A statistically significant correlation between the taste attractiveness and water solubility of amino acids was revealed in 2 species (chum salmon Oncorhynchus keta and navaga Eleginus nawaga), negative in both cases. The flavor, which stimulates food intake, was found to be more often intrinsic to acidic and polar uncharged than basic and nonpolar amino acids, L- than D-isomers, amino acids with an amino group at the α- than β-position. Amino acids are more attractive than their salts. Aromatic amino acids are much less attractive than S-containing or acyclic amino acids. Thus, in most fish species there is no or weak relationship between the taste attractiveness of free amino acids and many of their physical, chemical and biological properties, suggesting a mediated character of this relationship and/or its poor detectability.     

了哥王(Wikstroemia indica)的生态生物学特征

对了哥王的生态生物学特征研究表明 ,了哥王分布区气候条件温暖湿润 ,生境主要为草坡和开旷林地 .了哥王耐贫瘠 ,是一种阳生性灌木 ,其光合速率平均为 7.33μmolCO2 ·m-2 ·s-1.其竞争力明显弱于同在灌草丛中分布的桃金娘 .因而在灌草丛阶段的演替过程中 ,其种群减少 ,桃金娘种群增长 .了哥王体内加权平均养分含量为N 0 .6 6 7% ,P 0 .0 81% ,K 0 .5 4 0 % ,Ca 0 .776 % ,Mg 0 .2 5 9% .种群生物量分析表明 ,荒坡上野生了哥王生物量较低 ,仅 0 .0 2 73t·hm2 .若要大量开发了哥王资源 ,需要人工种植以提高生产量 .     

The genomic fingerprinting of the causative agents of sapronoses

The genome polymorphism of the causative agents of sapronoses (Vibrio cholerae, Legionella and Leptospira) has been studied. The use of the method of genome fingerprinting [correction of dactyloscopy] has been shown to permit the differentiation of closely related strains of such causative agents. The epidemically significant strains of the causative agents of sapronoses, isolated in different geographical regions, have been found to be genotypically related, i.e., they are probably of clonal origin. Avirulent and nontoxigenic strains are genotypically heterogeneous and differ both from one another and from epidemically significant strains. Using V. cholerae as an example, the hypothesis of the appearance of potentially dangerous variants at the epidemic period in the absence of their release at the period between epidemics is considered.     

Ecological and molecular maintenance strategies of mobile genetic elements

This review considers the influence of selection pressure, fitness and population structures on the evolution of mobile genetic elements (including plasmids, phage, pathogenicity islands, transposons and insertion sequences) that constitute the horizontal gene pool of bacteria. These are considered at different scales using examples from in vitro evolutionary studies of Escherichia coli and associated bacteriophage, detailed molecular analyses of the broad host-range IncP-1 plasmids, population surveys of pseudomonad plasmids and genomic comparisons of members of the Rhizobiaceae. All biological systems show genetic redundancy (the existence of allelic variation) at some population level, i.e. within a cell, a clone, population or community. We consider the level(s) at which redundancy is expressed and how this will affect and has influenced the evolution of mobile genetic elements.     

Species-forming involution of pathogenic bacteria as a biological pattern (exemplified by bacteria of the genus Moraxella)

The author advances a hypothesis stating that a species disappearing as a result of new conditions evolving in a colonized animal or human body, unfavorable for the existence of this species, does not become extinct, but reverts into newly developing species due to the loss of its properties and acquiring new properties corresponding to new conditions. Thus the genus is preserved through the loss of species characteristics by individual organisms. The advanced hypothesis is substantiated by the analysis of the relevant processes observed in cases of infectious keratoconjunctivitis in humans and cattle, caused by bacteria of the genus Moraxella. The data indicating the possibility of such reversion in the genera Neisseria and Bordetella are presented.     

Hydrobionts as reservoir hosts for infectious agents of bacterial sapronoses

Data on parasitism of the infectious agents of sapronoses in hydrobionts (protozoans, crustaceans, worms, mollusks, echinoderms, and fishes) are considered from the population-ecological viewpoint. The symbiotic relationships between populations of pathogenic bacteria and protozoans are of the host-parasite type. An ultrastructural analysis demonstrates that phagocytosis is incomplete both in planktonic forms and in biofilms formed by bacteria and protozoa. This provides for long-term survival of infectious agents in the environment. The migration of Yersinia pseudotuberculosis along trophic chains from the lowest to the highest level has been simulated experimentally. The long-term survival of pathogenic bacteria in aquatic animals and the ability of bacteria to migrate along trophic chains, reaching soil animals and humans, provide evidence that comprehensive studies on the routes of circulation of pathogens in natural ecosystems are highly relevant from the ecological and epidemiological viewpoints.     

Two dimensions of biodiversity research exemplified by nematomorpha and gastrotricha

Biodiversity research combines two dimensions, the horizontalone that contains species diversity, patterns among this diversityand its interconnections and the vertical one that deals withthe history of biodiversity, i.e., its phylogeny. With thesetight interconnections, the importance of so-called "lesserknown groups" such as Nematomorpha and Gastrotricha can be shown.Two examples are the life cycle of Nematomorpha and the phylogeneticposition of Gastrotricha. The life cycle of Nematomorpha isonly partially known and almost no conclusions can be made aboutthe impact of Nematomorpha on their hosts. For the phylogeneticposition of Gastrotricha, alternative hypotheses are available,mainly due to different results of morphological and molecular(18S rDNA) analyses. It is demonstrated how these differenthypotheses influence character interpretation and reconstructionamong Protostomia (Gastroneuralia).     

Nonlinear theory of coupled waves exemplified by beam-plasma instability

The nonlinear stage of instability of an annular electron beam spatially separated from an annular plasma is investigated. The equations describing coupled waves for an arbitrary ratio between the beam and plasma densities are derived. It is shown that instability saturates at distances on the order of several inverse spatial growth rates. The saturation is caused by relativistic nonlinearity, generation of the second harmonic, and low-frequency modulation of the electromagnetic field. At larger distances, resonant generation of low-frequency beam oscillations becomes a dominant factor. In the case of a low-density beam, an expression for the maximum power of the generated plasma wave is obtained in an explicit form.     

Identification of the causative agents of glanders and melioidosis by polymerase chain reaction

Burkholderia mallei and B. pseudomallei are causative agents of glanders and melioidosis, respectively, i.e. severe and fatal infection diseases of man and animal. The computer-based analysis of the 23S rRNA gene sites was used for selecting the primers. Two pairs of primers were chosen for the identification of B. mallei and Bpseudomallei. DNAs from 48 B. pseudomallei and 15 strains of B. mallei, unlike from other geterological bacteria, were positively amplified. Therefore, the method of polymerase chain reaction can be used in laboratory diagnosis of glanders and melioidosis.     

Biomonitoring of air pollution as exemplified by recent IAEA programs

Biomonitoring is an appropriate tool for assessing the levels of atmospheric pollution, having several advantages compared with the use of direct measurements of contaminants (e.g., in airborne particulate matter, atmospheric deposition, precipitation), related primarily to the permanent and common occurrence of the chosen organisms in the field, the ease of sampling, and trace element accumulation. Furthermore, biomonitors may provide a measure of integrated exposure over an extended period of time and are present in remote areas and no expensive technical equipment is involved in collecting them. They accumulate contaminants over the exposure time and concentrate them, thus facilitating analytical measurements. Based on largescale biomonitoring surveys, polluted areas can be identified, and by applying appropriate statistical tools, information can be obtained on the type of pollution sources and on the transboundary transport of atmospheric pollutants. The International Atomic Energy Agency is including the research on biomonitors in its projects on health-related environmental studies. Biomonitoring activities from several coordinated research projects on air pollution are presented, and results from an international workshop are discussed. In addition, activities in supporting improvement quality in the participating laboratories are outlined.     

Computer-assisted measurement of biomechanical values exemplified by the renovascular system

The high innovation in electronics and measuring techniques has influenced the development of medical equipment. The progressive miniaturization of integrated circuits yields in an increased possibility of functions with the respective technical equipments. Therewith also in medical technology more universal equipments are available. Unfortunately the development of sensors did not match the development rate in microelectronics. Hence computer-aided measuring (indirect measuring) becomes more and more important, to pick up normally non-measurable biomechanical quantities, which will be shown for the case study of the renovascular system.     

Arabidopsis genome analysis as exemplified by analysis of chromosome 4

During the last decade the small cruciferous plant Arabidopsis thaliana has become a model organism for flowering plants. Sequencing and analysis of the Arabidopsis genome is nearing completion. Beside an overview on methods and strategies for Arabidopsis genome analysis, a summary of the results from the first analysis is presented.This includes an overview on chromosomal organisation and topological features as well as a first comparison with other genomes.