Mechanistic Drivers of Flexibility in Summit Metabolic Rates of Small Birds

Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or environmental demands, thereby influencing fitness. Summit metabolic rate (M_sum = maximal thermogenic capacity) is one such flexible trait. Skeletal muscle and heart masses and myocyte metabolic intensity are potential drivers of M_sum flexibility in birds. We examined correlations of skeletal muscle and heart masses and pectoralis muscle citrate synthase (CS) activity (an indicator of cellular metabolic intensity) with M_sum in house sparrows (Passer domesticus) and dark-eyed juncos (Junco hyemalis) to determine whether these traits are associated with M_sum variation. Pectoralis mass was positively correlated with M_sum for both species, but no significant correlation remained for either species after accounting for body mass (M_b) variation. Combined flight and leg muscle masses were also not significantly correlated with M_sum for either species. In contrast, heart mass was significantly positively correlated with M_sum for juncos and nearly so (P = 0.054) for sparrows. Mass-specific and total pectoralis CS activities were significantly positively correlated with M_sum for sparrows, but not for juncos. Thus, myocyte metabolic intensity influences M_sum variation in house sparrows, although the stronger correlation of total (r = 0.495) than mass-specific (r = 0.378) CS activity with M_sum suggests that both pectoralis mass and metabolic intensity impact M_sum. In contrast, neither skeletal muscle masses nor pectoralis metabolic intensity varied with M_sum in juncos. However, heart mass was associated with M_sum variation in both species. These data suggest that drivers of metabolic flexibility are not uniform among bird species.     

Continuous limonin degradation by immobilizedRhodococcus fascians cells in K-carrageenan

Limonin can be effectively degraded byRhodococcus fascians cells. These bacteria can be entraped in -carrageenan, and used in a continuous stirred tank reactor to degrade limonin in a continuous process. The effects of temperature limonin concentration, dilution rate, and aeration on the reactor behaviour have been tested, and the results correlated with changes in limonin conversion, substrate degradation rate, and free and immobilized biomass. Results showed that the immobilized cells were able to debitter limonin-containing media and the immobilized biomass was quite stable throughout the operational conditions tested. A population of free biomass was present in the reactor, the quantity of which was dependent on dilution rate. The immobilized bacteria increased its limonin-degrading capability when the substrate concentration was increased. The aeration was not strictly necessary for limonin degradation. Additionally, the immobilized cells were active and stable for more than 2 months of continuous operation, and were able to recover their limonin-degrading capability when used intermittently. Finally, none of the main components of a juice was noticeably altered during limonin degradation, so the reactor response was good enough to consider its application.     

Recombinant Candida rugosa lipase 2 from Pichia pastoris: immobilization and use as biocatalyst in a stereoselective reaction

The characterization of the recombinant Candida rugosa Lip2 (r-Lip2) isoenzyme obtained from fed-batch cultures of Pichia pastoris under PAOX promoter was carried out, determining the optimal pH and temperature as well as their catalytic performance in both hydrolysis and synthesis reactions comparing with purified native Lip2 (n-Lip2) previously determined. The substrate specificity of r-Lip2 in hydrolysis reactions was determined with a series of triacylglycerols and p-nitrophenyl esters of variable acyl chain length. r-Lip2 showed the maximum specificity for both substrates towards medium-chain esters (C-8), similar behavior was observed with n-Lip2. However, significant differences were observed towards unsaturated substrates (triolein) or short-chain esters. A statistical design applied to study the effect of pH and temperature on lipase stability shown that r-Lip2, like n-Lip2, was more sensitive to pH than temperature changes. Nevertheless, the overall stability of soluble r-Lip2 was lower than soluble n-Lip2. The stability of r-lip2 was significantly improved by immobilization onto EP100, an excellent support for lipases with yields around 95% for offered lipolytic activity lower than 600 AU/mL. Finally, immobilized r-Lip2 was tested in the resolution of ibuprofen in isooctane by means of enantioselective esterification using 1-butanol as esterifying agent. r-Lip2 showed a better performance in terms of enantiomeric excess (74%) and enatiomeric factor (96%) than n-Lip2 (56 and 80%, respectively) for the same conversion (40%). Thus, r-Lip2 should be considered a good and pure biocatalyst, easy to produce and with a remaining activity of ca. 90% after one reaction cycle when immobilized on EP100.     

Introducing Acacia mangium trees in Eucalyptus grandis plantations: consequences for soil organic matter stocks and nitrogen mineralization

Background and aims

Eucalyptus plantations cover 20 million hectares on highly weathered soils. Large amounts of nitrogen (N) exported during harvesting lead to concerns about their sustainability. Our goal was to assess the potential of introducing A. mangium trees in highly productive Eucalyptus plantations to enhance soil organic matter stocks and N availability.

Methods

A randomized block design was set up in a Brazilian Ferralsol soil to assess the effects of mono-specific Eucalyptus grandis (100E) and Acacia mangium (100A) stands and mixed plantations (50A:50E) on soil organic matter stocks and net N mineralization.

Results

A 6-year rotation of mono-specific A. mangium plantations led to carbon (C) and N stocks in the forest floor that were 44% lower and 86% higher than in pure E. grandis stands, respectively. Carbon and N stocks were not significantly different between the three treatments in the 0–15?cm soil layer. Field incubations conducted every 4?weeks for the two last years of the rotation estimated net soil N mineralization in 100A and 100E at 124 and 64?kg?ha^?1?yr^?1, respectively. Nitrogen inputs to soil with litterfall were of the same order as net N mineralization.

Conclusions

Acacia mangium trees largely increased the turnover rate of N in the topsoil. Introducing A. mangium trees might improve mineral N availability in soils where commercial Eucalyptus plantations have been managed for a long time.     

Genome sequence, structural proteins, and capsid organization of the cyanophage Syn5: a "horned" bacteriophage of marine synechococcus

Marine Synechococcus spp and marine Prochlorococcus spp are numerically dominant photoautotrophs in the open oceans and contributors to the global carbon cycle. Syn5 is a short-tailed cyanophage isolated from the Sargasso Sea on Synechococcus strain WH8109. Syn5 has been grown in WH8109 to high titer in the laboratory and purified and concentrated retaining infectivity. Genome sequencing and annotation of Syn5 revealed that the linear genome is 46,214 bp with a 237 bp terminal direct repeat. Sixty-one open reading frames (ORFs) were identified. Based on genomic organization and sequence similarity to known protein sequences within GenBank, Syn5 shares features with T7-like phages. The presence of a putative integrase suggests access to a temperate life cycle. Assignment of 11 ORFs to structural proteins found within the phage virion was confirmed by mass-spectrometry and N-terminal sequencing. Eight of these identified structural proteins exhibited amino acid sequence similarity to enteric phage proteins. The remaining three virion proteins did not resemble any known phage sequences in GenBank as of August 2006. Cryo-electron micrographs of purified Syn5 virions revealed that the capsid has a single “horn”, a novel fibrous structure protruding from the opposing end of the capsid from the tail of the virion. The tail appendage displayed an apparent 3-fold rather than 6-fold symmetry. An 18 Å resolution icosahedral reconstruction of the capsid revealed a T = 7 lattice, but with an unusual pattern of surface knobs. This phage/host system should allow detailed investigation of the physiology and biochemistry of phage propagation in marine photosynthetic bacteria.     

Comparison of plate count agar and R2A medium for enumeration of heterotrophic bacteria in natural mineral water

In order to recover as many viable bacteria as possible from natural mineral water, in this study we have compared the counts obtained with the standard method (pour plate procedure with Plate Count Agar (PCA)) and counts with alternative test methods (PCA/spread plates, R2A medium/pour plates and R2A medium/spread plates). The results showed that counts with R2A medium/spread plates at 22°C and after a 7-day incubation period were more than 343% higher than those obtained with PCA/pour plate method. At 37°C and after a 3-day incubation period, the R2A pour plate technique gave counts about 368% greater than for the standard method. Moreover, while Pseudomonas, Comamonas and Acinetobacter species were isolated both from PCA and R2A medium, Flavobacterium spp. and Arthrobacter spp. were isolated only from R2A medium. For its higher productivity, R2A medium should be recommended for heterotrophic plate counts in natural mineral water.     

Protective impacts of household-based tuberculosis contact tracing are robust across endemic incidence levels and community contact patterns

There is an emerging consensus that achieving global tuberculosis control targets will require more proactive case finding approaches than are currently used in high-incidence settings. Household contact tracing (HHCT), for which households of newly diagnosed cases are actively screened for additional infected individuals is a potentially efficient approach to finding new cases of tuberculosis, however randomized trials assessing the population-level effects of such interventions in settings with sustained community transmission have shown mixed results. One potential explanation for this is that household transmission is responsible for a variable proportion of population-level tuberculosis burden between settings. For example, transmission is more likely to occur in households in settings with a lower tuberculosis burden and where individuals mix preferentially in local areas, compared with settings with higher disease burden and more dispersed mixing. To better understand the relationship between endemic incidence levels, social mixing, and the impact of HHCT, we developed a spatially explicit model of coupled household and community transmission. We found that the impact of HHCT was robust across settings of varied incidence and community contact patterns. In contrast, we found that the effects of community contact tracing interventions were sensitive to community contact patterns. Our results suggest that the protective benefits of HHCT are robust and the benefits of this intervention are likely to be maintained across epidemiological settings.     

Inhibition of elongation and H+ and K+ transport by the phosphodiesterase inhibitor aminophylline in plant tissue

Aminophylline, an inhibitor of cyclic nucleotide phosphodiesterase (EC 3.1.4.17), inhibits elongation and correlated H⁺ and K⁺ transport in embryos of Haplopappus gracilis and in pea internode segments. Moreover, the drug strongly inhibits the stimulation of these processes by fusicoccin and indole-3-acetic acid and reduces passive permeability of the membrane. The possible mechanisms of action of aminophylline are discussed.Abbreviations cAMP adenosine 3:5-cyclic monophosphate - FC fusicoccin - IAA indole-3-acetic acid - MES 2-N-morpholinoethanesulfonic acid - PDE cyclic nucleotide phosphodiesterase