Hierarchical Categorical Perception in Sensing and Cognitive Processes

This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical perception (CP) and categorical sensing (CS) in order to extend the CP framework to all communication processes in living systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing semiotic freedom observed in biological and cognitive systems.

Cloning, expression and interaction of human T-cell receptors with the bacterial superantigen SSA.

Superantigens (SAgs) are a class of disease-causing and immunostimulatory proteins of bacterial or viral origin that activate a large number of T-cells through interaction with the Vbeta domain of T-cell receptors (TCRs). In this study, recombinant TCR beta chains were constructed with human variable domains Vbeta5.2, Vbeta1 and Vbeta2.1, expressed as inclusion bodies, refolded and purified. The Streptococcus pyogenes SAg SSA-1 was cloned and expressed as a soluble periplasmic protein. SSA-1 was obtained both as a monomer and a dimer that has an intermolecular disulfide bond. We analyzed the biological activity of the recombinant SAgs by proliferation assays. The results suggest that SSA dimerization occludes the TCR interaction site. Naturally occurring SSA dimerization was also observed in supernatants of S. pyogenes isolates. An SSA mutant [SSA(C26S)] was produced to eliminate the Cys responsible for dimerization. Affinity assays using a resonant biosensor showed that both the mutant and monomeric wild type SSA have affinity for human Vbeta5.2 and Vbeta1 with Kd of 9-11 microm with a fast kass and a moderately fast kdiss. In spite of the reported stimulation of Vbeta2.1 bearing T-cells by SSA, we observed no measurable interaction.     

Factors shaping European rabbit abundance

This study analyses differences in European rabbitOryctolagus cuniculus (Linnaeus, 1758) abundance between fragmented and continuous populations and the relative importance of habitat structure (micro- and macrohabitat) and isolation in determining the abundance pattern in fragmented and continuous areas of central Spain. The species was mainly restricted to mediterranean vegetation habitat. In fragmented areas, rabbit abundance was linked to scrubland cover but was not correlated to pasture/cropland cover. The model explained very little of the observed variance. Distance to continuous populations did not improve the model. Stochastic phenomena or unmeasured factors (predation level, soil type) could be acting in this context. Rabbits were more abundant in continuous areas than in fragmented ones. In continuous areas, rabbit abundance was associated with mosaics of pastures, scrublands, and croplands. These habitat features are linked to shelter and feeding requirements of rabbits. The model explained an important part of the observed variance. This supports that management and conservation strategies should be based on the landscape pattern in each situation.     

Screening and catalytic activity in organic synthesis of novel fungal and yeast lipases

A total of 969 microbial strains were isolated from soil samples and tested to determine their lipolytic activity by employing screening techniques on solid and in liquid media. Ten lipase-producing microorganisms were selected and their taxonomic identification was carried out. From these strains Achremonium murorum, Monascus mucoroides, Arthroderma ciferri, Fusarium poae, Ovadendron sulphureo-ochraceum and Rhodotorula araucariae are described as lipase-producers for the first time. Hydrolysis activity of the crude lipases against both tributyrin and olive oil was measured. Heptyl oleate synthesis was carried out to test the activity of the selected lipases as biocatalysts in organic medium. All the selected lipases were tested as biocatalysts in several organic reactions using unnatural substrates. Lipases from the fungi Fusarium. oxysporum and O. sulphureo-ochraceum gave the best yields and enantioselectivities in the esterification of carboxylic acids. F. oxysporum and Penicillium chrysogenum lipases were the most active ones for the acylation of alcohols without steric hindrance. A. murorum lipase is very useful for the esterification of menthol. F. oxysporum and Fusarium. solani lipases were very stereoselective in the synthesis of carbamates.     

Differential effects of coinoculations with Pseudomonas jessenii PS06 (a phosphate-solubilizing bacterium) and Mesorhizobium ciceri C-2/2 strains on the growth and seed yield of chickpea under greenhouse and field conditions

In the course of a project carried out in two regions of Spain, Castilla y León and Andalucía, aiming to find useful biofertilizers for staple grain-legumes, an efficient rhizobia nodulating chickpea (termed as C-2/2) and a powerful in vitro phosphate-solubilizing bacterial strain (termed as PS06) were isolated. Analyses of their 16S rDNA sequence indicated that they belong to the bacterial species Mesorhizobium ciceri and Pseudomonas jessenii, respectively. Greenhouse and field experiments were carried out in order to test the effect of single and dual inoculations on chickpea (ecotype ILC-482) growth. Under greenhouse conditions, plants inoculated with Mesorhizobium ciceri C-2/2 alone had the highest shoot dry weight. The inoculation treatment with P. jessenii PS06 yielded a shoot dry weight 14% greater than the uninoculated control treatment, but it was not correlated with shoot P contents. However, the co-inoculation of C-2/2 with PS06 resulted in a decrease in shoot dry weight with respect to the inoculation with C-2/2 alone. Under field conditions, plants inoculated with M. ciceri C-2/2, in single or dual inoculation, produced higher nodule fresh weight, nodule number and shoot N content than the other treatments. Inoculation with P. jessenii PS06 had no significant effect on plant growth. However, the co-inoculation treatment ranked the highest in seed yield (52% greater than the uninoculated control treatment) and nodule fresh weight. These data suggest that P. jessenii PS06 can act synergistically with M. ciceri C-2/2 in promoting chickpea growth. The contrasting results obtained between greenhouse and field experiments are discussed.     

Flight behaviour of Encarsia formosa in response to plant and host stimuli

The flight behaviour of Encarsia formosa Gahan (Hymenoptera: Aphelinidae), a parasitoid of Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) has been studied in response to the following natural components: bean plant (Phaseolus vulgaris L.) infested with T. vaporariorum (PHC, plant host complex), host damaged bean plant from which whiteflies were removed (HDP, host damaged plant), T. vaporariorum third instar larvae (H, host), uninfested bean plant (P, plant) and T. vaporariorum empty pupal cases (EPC, empty pupal cases). A combination of chemical and visual stimuli is necessary in host location from a distance by E. formosa and seems to deeply affect the dispersal of this parasitoid. The presence of host (PHC, H) or of its parts (EPC) led to a substantial increase of oriented flights suggesting the occurrence of host derived chemicals. At a closer range, a combination of visual and chemical stimuli deriving from all the components of the plant host complex elicited the transition flying-landing and the following landing on the source.     

A new lupene diol from Dodonaea attenuata

Lup-20(29)-ene-3β,11β-diol and lupeol have been isolated from Dodonaea attenuata A. Cunn. var. linearis Benth.     

Production of vitamin B12 in an upflow anaerobic filter continuous reactor using Acetobacterium sp.

The accumulation of biofilm by Acetobacterium sp. during continuous culture in an upflow anaerobic filter (UAF) growing on methanol-formate was the result of space velocity and inlet concentrations of substrate and Co⁺². To achieve good development of biofilm, a space velocity of 0.38 h^–1, inlet substrate concentrations of 125 mM of both methanol and formate, and Co⁺² at 0.16 mM were required. Cell productivities in the effluent of the UAF-reactor were about 6-fold higher than in chemostat cultures (0.20 g l^–1 h^–1 for UAF and 0.035 g l^–1 h^–1 for chemostat) (previous studies), and the maximum vitamin B₁₂ specific concentration was 5.1 mg g cell^–1.     

Binding of [3H]-2-isobutyl-3-methoxypyrazine to cow olfactory mucosa

The odorant 2-isobutyl-3-methoxypyrazine binds to cow olfactorymucosa homogenate. The complex, which can be separated by gelfiltration on Sephadex G-100, appears to be made up of fourmacromolecular species. No significant binding has been measuredwith respiratory epithelium. The binding disappears after treatmentwith proteolytic enzymes, or in a SDS containing buffer, thusindicating that the receptors are proteins. Complete loss ofbinding capacity has been also observed as a consequence ofdialysis: this suggests the involvement of a low molecular weightcomponent.