Temperature-dependent development of <Emphasis Type="Italic">Macrolophus pygmaeus</Emphasis> and its applicability to biological control

A linear model and three nonlinear models (Logan type III, Lactin and Brière) were applied to Macrolophus pygmaeus (Rambur) (Hemiptera: Miridae) at constant temperatures and validated under diel temperature variation, and field conditions. Complete development from egg to adult, with >80% survivorship, occurred at nine constant temperatures between 15 and 32 °C. Total developmental time decreased from a maximum at 15 °C (68.48 days) to a minimum at 30 °C (18.69 days) and then increased at 32 °C (23.44 days). Optimal survival and the highest developmental rate occurred within the range of 27–30 °C. The adjusted determination coefficients were high for linear and nonlinear models (>0.89). Field validation showed high levels of accuracy in all models (≥93.4%). These valid mathematical models contribute to optimal application, field management, and mass rearing of M. pygmaeus for its applicability to biological control.     

Different blocking effects of HgCl2 and NaCl on aquaporins of pepper plants

In this study we have compared the short-term effects of both NaCl and HgCl₂ on aquaporins of Capsicum annuum L. plants, in order to determine whether or not they are similar. Stomatal conductance, turgor, root hydraulic conductance and water status were measured after 0.5, 2, 4 and 6 h of NaCl (60 mmol/L) or HgCl₂ (50 μmol/L) treatment. When 60 mmol/L NaCl was added to the nutrient solution, a large decrease in stomatal conductance was observed after 2 h. However, when HgCl₂ (50 μmol/L) was added, the decrease occurred after 4 h. The number of open stomata closed was always lower in plants treated with HgCl₂ than in plants treated with NaCl. The water content of the Hg²⁺-treated plants was decreased, compared with controls and NaCl-treated. The root hydraulic conductance decreased after HgCl₂ and NaCl treatment plants. Turgor of leaf epidermal cells was greatly reduced in plants treated with HgCl₂, but remained constant in the NaCl treatment, compared with control plants. The fact that the stomatal conductance was reduced more rapidly after NaCl addition, followed by the stomatal closure, and that both water content and turgor did not differ from the control suggests that in NaCl-treated plants there must be a signal moving from root to shoot. Therefore, the control of plant homeostasis through a combined regulation of root and stomatal exchanges may be dependent on aquaporin regulation.     

A new method to determine the aw range in which immobilized lipases display optimum activity in organic media

Summary We describe a qualitative method to predict the pre-equilibration a_w, system value in which, covalent immobilized lipase B from Candida antarctica to sepharose and silica, displayed best synthetic activity. The methodology is based in the analysis of the water adsorption isotherms of the biocatalyst in air and in the organic solvent. The biocatalyst is active at pre-equilibration a_w values higher than the divergence point between both isotherms. In addition, native and immobilized lipase display highest activity if the biocatalyst is pre-equilibrated at a_w=P point. For preparative purposes, the validity of the method was proved in the esterification of racemic 2-(4-isobutyl phenyl) propionic acid with 1-propanol in isooctane at long reaction time.     

Microplate-based high throughput screening procedure for the isolation of lipid-rich marine microalgae

Background

Termites are highly effective at degrading lignocelluloses, and thus can be used as a model for studying plant cell-wall degradation in biological systems. However, the process of lignin deconstruction and/or degradation in termites is still not well understood.

Methods

We investigated the associated structural modification caused by termites in the lignin biomolecular assembly in softwood tissues crucial for cell-wall degradation. We conducted comparative studies on the termite-digested (i.e. termite feces) and native (control) softwood tissues with the aid of advanced analytical techniques: ¹³C crosspolarization magic angle spinning and nuclear magnetic resonance (CP-MAS-NMR) spectroscopy, flash pyrolysis with gas chromatography mass spectrometry (Py-GC/MS), and Py-GC-MS in the presence of tetramethylammonium hydroxide (Py-TMAH)-GC/MS.

Results

The ¹³C CP/MAS NMR spectroscopic analysis revealed an increased level of guaiacyl-derived (G unit) polymeric framework in the termite-digested softwood (feces), while providing specific evidence of cellulose degradation. The Py-GC/MS data were in agreement with the ¹³C CP/MAS NMR spectroscopic studies, thus indicating dehydroxylation and modification of selective intermonomer side-chain linkages in the lignin in the termite feces. Moreover, Py-TMAH-GC/MS analysis showed significant differences in the product distribution between control and termite feces. This strongly suggests that the structural modification in lignin could be associated with the formation of additional condensed interunit linkages.

Conclusion

Collectively, these data further establish: 1) that the major β-O-4' (β-aryl ether) was conserved, albeit with substructure degeneracy, and 2) that the nature of the resulting polymer in termite feces retained most of its original aromatic moieties (G unit-derived). Overall, these results provide insight into lignin-unlocking mechanisms for understanding plant cell-wall deconstruction, which could be useful in development of new enzymatic pretreatment processes mimicking the termite system for biochemical conversion of lignocellulosic biomass to fuels and chemicals.     

The importance of fine-scale breeding site selection patterns under a landscape-sharing approach for wolf conservation

For large carnivores persisting in human-dominated landscapes, conservation planning is often hindered by the large spatial requirements of these species, availability of protected areas, and human land uses. Protected areas are usually too small to support viable populations, and scattered across a human land-use matrix. Therefore, large carnivore conservation should be planned at large spatial scales under a land-sharing approach (allowing the coexistence between large carnivores and people in the same landscape), which means increasing the focus on the human-dominated matrix. Most of the critical factors determining large carnivore persistence (i.e., those related to food availability and vulnerability to humans) interact synergistically in space and time during the breeding season. Here, using as a case study a wolf population in NW Iberia, we studied fine-scale breeding site selection patterns (1 and 9 km²) in relation to human pressure, and the availability of food and refuge. The selection of wolf breeding sites in this human-dominated landscape was not determined by potential availability of prey biomass in the immediate vicinity (1 km²). However, wolves selected breeding sites with high availability of refuge (concealing vegetation), and low human accessibility and activity levels. Paved roads showed the highest proportion of independent contribution to explaining breeding site selection patterns (negative influence), being followed by refuge availability (positive influence) and the remoteness of breeding sites in relation to the surrounding spatial context (positive influence). Refuge availability, even at very small spatial scales taking into account the spatial requirements of wolves, may compensate for moderate levels of human activities in the vicinity of breeding sites. The strength of breeding selection patterns varied along a hierarchical process at different spatial scales. Under a landscape-sharing approach, integrating key processes observed in the human-dominated matrix, such as breeding site selection patterns, into landscape planning is of paramount importance for carnivore conservation. By temporally restricting human use on breeding sites and small portions of surrounding lands (~ 1 km²), and by maintaining several small refuge areas interspersed within the human-dominated matrix, we could favor wolf persistence without reducing land availability for other uses, improving the conditions for coexistence between wolves and humans.     

Worldwide Occurrence of Integrative Conjugative Element Encoding Multidrug Resistance Determinants in Epidemic Vibrio cholerae O1

In the last decades, there has been an increase of cholera epidemics caused by multidrug resistant strains. Particularly, the integrative and conjugative element (ICE) seems to play a major role in the emergence of multidrug resistant Vibrio cholerae. This study fully characterized, by whole genome sequencing, new ICEs carried by multidrug resistant V. cholerae O1 strains from Nigeria (2010) (ICEVchNig1) and Nepal (1994) (ICEVchNep1). The gene content and gene order of these two ICEs are the same, and identical to ICEVchInd5, ICEVchBan5 and ICEVchHai1 previously identified in multidrug resistant V. cholerae O1. This ICE is characterized by dfrA1, sul2, strAB and floR antimicrobial resistance genes, and by unique gene content in HS4 and HS5 ICE regions. Screening for ICEs, in publicly available V. cholerae genomes, revealed the occurrence and widespread distribution of this ICE among V. cholerae O1. Metagenomic analysis found segments of this ICE in marine environments far from the direct influence of the cholera epidemic. Therefore, this study revealed the epidemiology of a spatio-temporal prevalent ICE in V. cholerae O1. Its occurrence and dispersion in V. cholerae O1 strains from different continents throughout more than two decades can be indicative of its role in the fitness of the current pandemic lineage.     

The metabolic core and catalytic switches are fundamental elements in the self-regulation of the systemic metabolic structure of cells

Background

Experimental observations and numerical studies with dissipative metabolic networks have shown that cellular enzymatic activity self-organizes spontaneously leading to the emergence of a metabolic core formed by a set of enzymatic reactions which are always active under all environmental conditions, while the rest of catalytic processes are only intermittently active. The reactions of the metabolic core are essential for biomass formation and to assure optimal metabolic performance. The on-off catalytic reactions and the metabolic core are essential elements of a Systemic Metabolic Structure which seems to be a key feature common to all cellular organisms.

Methodology/Principal Findings

In order to investigate the functional importance of the metabolic core we have studied different catalytic patterns of a dissipative metabolic network under different external conditions. The emerging biochemical data have been analysed using information-based dynamic tools, such as Pearson''s correlation and Transfer Entropy (which measures effective functionality). Our results show that a functional structure of effective connectivity emerges which is dynamical and characterized by significant variations of bio-molecular information flows.

Conclusions/Significance

We have quantified essential aspects of the metabolic core functionality. The always active enzymatic reactions form a hub –with a high degree of effective connectivity- exhibiting a wide range of functional information values being able to act either as a source or as a sink of bio-molecular causal interactions. Likewise, we have found that the metabolic core is an essential part of an emergent functional structure characterized by catalytic modules and metabolic switches which allow critical transitions in enzymatic activity. Both, the metabolic core and the catalytic switches in which also intermittently-active enzymes are involved seem to be fundamental elements in the self-regulation of the Systemic Metabolic Structure.