Phenotypic and genotypic characterization of competitive exclusion products for use in poultry

AIMS: Phenotypic and genotypic bacteria identification methods were compared for their efficacy in determining the composition of competitive exclusion (CE) products. METHODS AND RESULTS: Phenotypic methods used for bacterial identification were fatty acid methyl ester profiles, biochemical assays and carbohydrate utilization profiles. Genotypic methods were MicroSeq16S rRNA sequence analysis and BLAST searches of the GenBank sequence database. Agreement between phenotypic and genotypic methods for identification of bacteria isolated from the Preempt CE product was 20%. A defined test mixture of bacteria was identified to the species level 100% by BLAST analysis, 64% by MicroSeq and 36% by phenotypic techniques. CONCLUSIONS: The wide range of facultative and obligate anaerobic bacteria present in a CE product are more accurately identified with 16S rRNA sequence analyses than with phenotypic identification techniques. SIGNIFICANCE AND IMPACT OF THE STUDY: These results will provide guidelines for manufacturers of CE products to submit more reliable product information for market approval by regulatory agencies.     

Comparison of cardiopulmonary responses to two types of dry-land upper-body exercise testing modes in competitive swimmers

In this study we compared cardiopulmonary responses to upper-body exercise in 12 swimmers, using simulation of the front-crawl arm-pulling action on a computer-interfaced isokinetic swim bench and arm cranking on a modified cycle ergometer. Subjects adopted a prone posture; exercise was initially set at 20 W and subsequently increased by 10 W. min(-1). The tests were performed in a randomised order at the same time of day, within 72 h. The highest (peak) oxygen consumption (VO(2peak)), heart rate (HR(peak)), blood lactate ([la(-)](peak)) and exercise intensity (EI(peak)) were recorded at exhaustion. Mean (SEM) peak responses to simulated swimming were higher than those to arm cranking for VO(2peak) [2.9 (0.2) vs 2.4 (0.1) l x min(-1); P = 0.01], HR(peak) [174 (2) vs 161 (2) beats x min(-1); P = 0.03], and EI(peak) [122 (6) vs 102 (5) W; P = 0.02]. However, there were no significant differences in [la(-)](peak) [9.6 (0.6) vs 8.2 (0.6) mmol x l(-1); P = 0.08]. Thus simulated swimming is the preferred form of dry-land ergometry for the assessment of swimmers.     

On the competitive exclusion principle

The Competitive Exclusion Principle, formulated by V. Volterra (Memorie del R. Comitato Talassografico Italiano,131, 1–142, 1927) for a number of species competing for a common ecological niche, is extended to a number of species competing for many ecological niches. Supported by an N.I.H. training grant.     

Aggregation and the competitive exclusion principle

A mathematical model for aggregation in a single animal population is set up. It relies on two premises. First, there is an advantage to individuals in the population in grouping together, for example for social purposes or to reduce the risk of predation. Second, the intra-specific competition at a point depends not simply on the population density at that point but on the average population density near the point, since the animals may move to find resources. The model is then extended to competing populations, and inter-specific competition is also assumed to depend on an average population density. It is shown that the resulting aggregation may lead to the co-existence of populations one of which would otherwise be excluded by the other. This finding is discussed with regard to the Competitive Exclusion Principle.     

Comparison of two methods for quality assessment of macroalgae assemblages,under different pollution types

The selection of adequate methodologies for the assessment of different biological quality elements is urgently needed for the application of the water framework directive (WFD 2000/60/EEC). In the case of macroalgae in coastal waters of the North East Atlantic, two methodologies have been proposed: the reduced species list (RSL) index and the quality of rocky bottoms (CFR) index. Both methods use multimetric approaches to evaluate the quality of macroalgae assemblages, which are based on community characteristics (species/populations richness, cover, percentage of opportunistic species, ecological state groups ratio, etc.). In this paper the results of applying both indices on three different types of pollution gradients in the North coast of Spain (bay of Biscay) are presented, in order to test their usefulness and intercalibration possibilities. In general terms, the CFR index responded more accurately than the RSL index to the pollution gradients under study. With respect to the indicators used in the current evaluation, richness, opportunistic species and cover seemed to be the most accurate for quality assessment of macroalgal communities. While the first two indicators are taken into account in both indices, the latter (cover) is only considered in the CFR index, even though the abundance of macroalgae is one of the aspects to be included in the evaluation of this biological element, according to the WFD.     

Species-level selection reduces selfishness through competitive exclusion

Adaptation does not necessarily lead to traits which are optimal for the population. This is because selection is often the strongest at the individual or gene level. The evolution of selfishness can lead to a 'tragedy of the commons', where traits such as aggression or social cheating reduce population size and may lead to extinction. This suggests that species-level selection will result whenever species differ in the incentive to be selfish. We explore this idea in a simple model that combines individual-level selection with ecology in two interacting species. Our model is not influenced by kin or trait-group selection. We find that individual selection in combination with competitive exclusion greatly increases the likelihood that selfish species go extinct. A simple example of this would be a vertebrate species that invests heavily into squabbles over breeding sites, which is then excluded by a species that invests more into direct reproduction. A multispecies simulation shows that these extinctions result in communities containing species that are much less selfish. Our results suggest that species-level selection and community dynamics play an important role in regulating the intensity of conflicts in natural populations.     

A competitive exclusion principle for pathogen virulence

For a modified Anderson and May model of host parasite dynamics it is shown that infections of different levels of virulence die out asymptotically except those that optimize the basic reproductive rate of the causative parasite. The result holds under the assumption that infection with one strain of parasite precludes additional infections with other strains. Technically, the model includes an environmental carrying capacity for the host. A threshold condition is derived which decides whether or not the parasites persist in the host population.Supported by a Heisenberg scholarship of Deutsche Forschungsgemeinschaft     

The present status of the competitive exclusion principle

Since Darwin accepted the Malthusian population theory to solve the demographic problems he thought to be logically connected with the universal operation of natural selection, the numerical processes in both populations and communities were generally supposed to be governed by competition. For interspecific relations this found expression in the 'competitive exclusion principle'. After it was shown that coexistence rather than exclusion of closely related species is the rule, this principle gradually changed into the 'competitive niche shift principle'. Recently the universality of competition has been increasingly questioned, so that other interspecific relationships (especially predation) are revaluated as possibly governing many natural population and inter-population processes.     

Temperature mediates competitive exclusion and diversity in benthic microalgae under different N:P stoichiometry

The dependence of competitive interactions on abiotic conditions is attracting increasing interest in the face of globally rising temperatures and altered biogeochemical cycles of major nutrients. In a microcosm experiment involving a natural inoculum of benthic microalgae, temperature and nutrient supply ratios were manipulated in order to test three main hypotheses: (1) temperature and nutrient supply ratios determine species composition and diversity of the assemblage, (2) the identity of the dominating species depends on nutrient supply and temperature, and (3) higher temperature leads to faster competitive exclusion and thus more rapid decline in species richness. Over a period of 7 weeks, algal biomass reached an equilibrium carrying capacity, with was higher at colder temperatures and intermediate N:P supply ratios (N:P = 16). Initial growth rate increased with temperature and under high P-supply. Species richness in the stationary phase of the experiment decreased with increasing temperature, reflecting a higher extinction rate in the warmer treatments, which were also characterized by higher dominance of single species. Thus, increasing temperature both altered the identity of the dominating species and accelerated competitive displacement. This experiment thus indicates that warming might influence outcome and temporal dynamics in species interactions, and thereby eventually local diversity.     

Comparison of different types of biomasses for copper biosorption

Three biomass, birch wood Betula sp., marine brown alga Fucus vesiculosus, and terrestrial moss Pleurozium schreberi, have been compared as raw materials for preparation of biosorbents for removal of copper ions from diluted water solutions. Small sample doses (0.5 g/100ml) of the biosorbents prepared from alga and moss enabled more than 90% removal of Cu(II) ions from diluted water solutions (5-20mg/l). The sample from sawdust was less effective. A pseudo-second-order rate model properly described the experimental kinetic data for the biosorbents. The maximum sorption capacities (Xm) determined from the experimental equilibrium isotherms by applying the Langmuir model showed that the alga had the best copper-binding ability (Xm=23.4 mg/g), followed by the moss (Xm=11.1mg/g), and the sawdust (Xm=4.9 mg/g). No visible damages or performance losses were detected for the alga and moss after five sorption-desorption cycles using diluted HCl as eluent.     

Mutual exclusion versus coexistence for discrete competitive systems

Using discrete competition models where the density dependent growth functions are either all exponential or all rational, notwithstanding the complex interactions of the species, we establish an exclusion principle. Moreover, in a 2-species discrete competition model where the growth functions are exponential and rational, an example is given illustrating coexistence when our conditions are satisfied. We obtain an exclusion principle for this 2-species model for some choice of parameters.Research partially supported by funds provided by a Science and Education Grant to the USDA-Forest Service, Southeastern Forest Experiment Station, Population Genetics of Forest Trees Research Unit, Raleigh, North Carolina     

Comparison of organic matter degradation and microbial community during thermophilic composting of two different types of anaerobic sludge

Changes in organic matter degradation and microbial communities during thermophilic composting were compared using two different types of anaerobic sludge, one from mesophilic methane fermentation, containing a high concentration of proteins (S-sludge), and the other from thermophilic methane fermentation, containing high concentrations of lipids and fibers (K-sludge). The difference in the organic matter degradation rate corresponded to the difference in the organic matter constituents; the CO(2) evolution rate was greater in the composting of S-sludge than of K-sludge; moreover, the NH(3) evolution resulting from the protein degradation was especially higher in the composting of S-sludge. Then the differences in the microbial communities that contributed to each composting were determined by the PCR-DGGE method. Ureibacillus sp., which is known as a degrader with high organic matter degradation activity, was observed during the composting of S-sludge, whereas Thermobifida fusca, which is a well known thermophilic actinomycete that produces enzymes for lignocellulose degradation, were observed during the composting of K-sludge.     

Comparison of two different lysozyme types under native and crystallization conditions using two-dimensional NMR and dynamic light scattering

In order to elucidate differences observed in the aggregation kinetics of hen-egg white lysozyme under crystallization conditions we have undertaken a comparative study of the enzyme marketed by Seikagaku and Sigma companies. When the crystallization of the two lysozyme preparations is followed by time-resolved dynamic light scattering, the structural differences are also observed under native conditions in the early nucleation kinetics. The differences are manifested in the formation rates of macroscopic crystals, but do not influence the morphology of the typical tetragonal lysozyme crystal. Using two-dimensional NMR we have followed the differences in the native-like solution structure of the two preparations, while the primary sequence and molecular mass are identical. According to the published structure of tetragonal lysozyme crystal the largest deviations were found for the residues involved in the intermolecular interactions in crystal structure.     

Complex food webs prevent competitive exclusion among producer species

Herbivorous top-down forces and bottom-up competition for nutrients determine the coexistence and relative biomass patterns of producer species. Combining models of predator-prey and producer-nutrient interactions with a structural model of complex food webs, I investigated these two aspects in a dynamic food-web model. While competitive exclusion leads to persistence of only one producer species in 99.7% of the simulated simple producer communities without consumers, embedding the same producer communities in complex food webs generally yields producer coexistence. In simple producer communities, the producers with the most efficient nutrient-intake rates increase in biomass until they competitively exclude inferior producers. In food webs, herbivory predominantly reduces the biomass density of those producers that dominated in producer communities, which yields a more even biomass distribution. In contrast to prior analyses of simple modules, this facilitation of producer coexistence by herbivory does not require a trade-off between the nutrient-intake efficiency and the resistance to herbivory. The local network structure of food webs (top-down effects of the number of herbivores and the herbivores' maximum consumption rates) and the nutrient supply (bottom-up effect) interactively determine the relative biomass densities of the producer species. A strong negative feedback loop emerges in food webs: factors that increase producer biomasses also increase herbivory, which reduces producer biomasses. This negative feedback loop regulates the coexistence and biomass patterns of the producers by balancing biomass increases of producers and biomass fluxes to herbivores, which prevents competitive exclusion.     

Pioneer exclusion in a one-hump discrete pioneer-climax competitive system

One-hump maps as single species pioneer and climax ecological models confirm the expected pioneer exclusion in an uninterrupted two dimensional discrete pioneer-climax competition model. Other dynamic situations occur in such models. In particular a mutual exclusion principle is presented as a mathematical theorem.     

Mutarotation of hydrolysis products by different types of exo-cellulases from Trichoderma viride.

Mutarotation of products from p-nitrophenyl beta-D-cellobioside and cellopentaitol by two different types of exo-cellulases from Trichoderma viride was investigated. It was found that an exo-cellulase of glucosidase type produced from the former substrate D-glucose which was mutarotated in a downward direction, while another exo-cellulase of Avicelase type produced from the latter substrate cellobiose which was mutarotated in an upward direction.     

不同耐旱性大麦品种叶片发育的研究

选用耐旱性不同的两个大麦品种作为研究对象,分析其叶片结构的异同。结果表明:两个大麦品种的叶片发育可以分为幼叶萌发期、幼叶抽出期、幼叶生长期和叶片成熟期四个阶段,其中在幼叶萌发期,叶片结构无明显差异。经PAS染色,从幼叶生长期开始,耐旱性弱的Moroc 9-75,含淀粉粒的叶肉细胞少,淀粉粒颗粒小; 耐旱性强的HS 41-1,含淀粉粒的叶肉细胞多,淀粉粒颗粒大。遭受干旱胁迫后,两个品种的植株长势明显较弱,叶片短而窄; 表皮细胞角质层变厚,叶片中叶肉细胞变小,叶肉细胞胞间隙变大,叶肉细胞破裂现象增多; PAS染色反应显示,含淀粉粒的叶肉细胞减少,淀粉粒颗粒变小或基本没有; HS 41-1解体的细胞不如Moroc 9-75多。因此,在光镜下,叶片结构的差异,特别是细胞含有的淀粉粒大小与数量的区别,是植物对水分胁迫的一种适应; 同时叶脉对植物刚性的影响较大。