Calorific values of Chlorella vulgaris (Trebouxiophyceae) as a function of different phosphorus concentrations

Quantification of the calorific content of microalgae is critical in studies of energy flow, trophic partitioning, plant/herbivore interactions in aquaculture and biomass production for biofuels. We investigated the calorific value and biochemical composition of Chlorella vulgaris at different phosphorus (P) concentrations (6.0 × 10^?7, 2.3 × 10^?6 and 2.3 × 10^?4 mol L^?1 P). As expected, the control (2.3 × 10^?4 mol L^?1 P) supported better growth than P limited treatments. Biomolecules like total carbohydrates and lipids accumulated under P limitation, which significantly correlated with high calorific values. Lipid class composition showed that triacylglycerols were the most accumulated under P limited conditions. The calorific value reported under control conditions (13.78 kJ g^?1) was less than those obtained under P limitation (30.47–33.07 kJ g^?1). The highest calorific value with less growth retardation was obtained at 2.3 × 10^?6 mol L^?1 P.     

Ddi1-like protein from Leishmania major is an active aspartyl proteinase

Eukaryotic cells respond to DNA damage by activating damage checkpoint pathways, which arrest cell cycle progression and induce gene expression. We isolated a full-length cDNA encoding a 49-kDa protein from Leishmania major, which exhibited significant deduced amino acid sequence homology with the annotated Leishmania sp. DNA damage-inducible (Ddi1-like) protein, as well as with the Ddi1 protein from Saccharomyces cerevisiae. In contrast to the previously described Ddi1 protein, the protein from L. major displays three domains: (1) an NH2-terminal ubiquitin like; (2) a COOH terminal ubiquitin-associated; (3) a retroviral aspartyl proteinase, containing the typical D[S/T]G signature. The function of the L. major Ddi1-like recombinant protein was investigated after expression in baculovirus/insect cells and biochemical analysis, revealing preferential substrate selectivity for aspartyl proteinase A₂ family substrates, with optimal activity in acidic conditions. The proteolytic activity was inhibited by aspartyl proteinase inhibitors. Molecular modeling of the retroviral domain of the Ddi1-like Leishmania protein revealed a dimer structure that contained a double Asp-Ser-Gly-Ala amino acid sequence motif, in an almost identical geometry to the exhibited by the homologous retroviral aspartyl protease domain of yeast Ddi1 protein. Our results indicate that the isolated Ddi1-like protein is a functional aspartyl proteinase in L. major, opening possibility to be considered as a potential target for novel antiparasitic drugs.     

Contrasting phylogenetic patterns of anther smuts (Pucciniomycotina: Microbotryum) reflect phylogenetic patterns of their caryophyllaceous hosts

Anther smuts in the genus Microbotryum often show very high host specificity toward their caryophyllaceous hosts, but some of the larger host groups such as Dianthus are crucially undersampled for these parasites so that the question of host specificity cannot be answered conclusively. In this study we sequenced the internal transcribed spacer (ITS) region of members of the Microbotryum dianthorum species complex as well as their Dianthus hosts. We compared phylogenetic trees of these parasites including sequences of anther smuts from other Caryophyllaceae, mainly Silene, with phylogenies of Caryophyllaceae that are known to harbor anther smuts. Additionally we tested whether observed patterns in parasites are due to shared ancestry or if geographic separation is a factor that should be taken into consideration in delimitating species. Parasites on Dianthus showed mainly an arbitrary distribution on Dianthus hosts, whereas parasites on other Caryophyllaceae formed well-supported monophyletic clades that corresponded to restricted host groups. The same pattern was observed in the Caryophyllaceae studied: morphologically described Dianthus species did not correspond well with monophyletic clades based on molecular data, whereas other Caryophyllaceae mainly did. We suggest that these different patterns primarily result from different breeding systems and speciation times between different host groups as well as difficulties in species delimitations in the genus Dianthus.     

Rab11‐Family of Interacting Protein 2 associates with chlamydial inclusions through its Rab‐binding domain and promotes bacterial multiplication

Chlamydia trachomatis, an obligate intracellular pathogen, survives within host cells in a special compartment named ‘inclusion’ and takes advantage of host vesicular transport pathways for its growth and replication. Rab GTPases are key regulatory proteins of intracellular trafficking. Several Rabs, among them Rab11 and Rab14, are implicated in chlamydial development. FIP2, a member of the Rab11‐Family of Interacting Proteins, presents at the C‐terminus a Rab‐binding domain that interacts with both Rab11 and Rab14. In this study, we determined and characterized the recruitment of endogenous and GFP‐tagged FIP2 to the chlamydial inclusions. The recruitment of FIP2 is specific since other members of the Rab11‐Family of Interacting Proteins do not associate with the chlamydial inclusions. The Rab‐binding domain of FIP2 is essential for its association. Our results indicate that FIP2 binds to Rab11 at the chlamydial inclusion membrane through its Rab‐binding domain. The presence of FIP2 at the chlamydial inclusion favours the recruitment of Rab14. Furthermore, our results show that FIP2 promotes inclusion development and bacterial replication. In agreement, the silencing of FIP2 decreases the bacterial progeny. C. trachomatis likely recruits FIP2 to hijack host intracellular trafficking to redirect vesicles full of nutrients towards the inclusion.     

Plant communities and environmental factors in the Guayana Highlands: monitoring for conservation under future climate change

The Guayana Highlands (GH) constitute a highly diverse, but relatively poorly studied Neotropical biome, comprised of ～50 flat-topped mountain summits (called tepuis). Previous studies based on warming forecasts for the region suggested that an upward displacement of environmental conditions of 500–700 m could occur by 2100, potentially resulting in the extinction of c. 50% of its endemic flora due to total habitat loss. To assess the ecological responses of the species to climate change, and select the appropriate conservation measures, long-term monitoring of the GH plant communities will be necessary. In this study, the baseline state for future comparisons was established for the best explored tepui in terms of its flora, Roraima-tepui (2810 m), through a floristic characterization of its different vegetation types. We also identified the environmental gradients underlying the major plant communities, and assessed the effects of human activities on the chemistry of soils and water at three field camps. Our results yielded five main community types: three meadows, one shrubland, and one forest, with their corresponding diagnostic species. The herbaceous communities were mainly influenced by the presence of flat sandy soils, with varying flooding capacity. Shrublands and forests were characterized by irregular organic soils with very low pH. Finally, pH values below 3 were measured on an organic soil of a field camp, although further studies will be necessary to attribute this deviation to human activities.     

PI3K p110δ Is Expressed by gp38?CD31+ and gp38+CD31+ Spleen Stromal Cells and Regulates Their CCL19, CCL21, and LTβR mRNA Levels

The role of p110δ PI3K in lymphoid cells has been studied extensively, showing its importance in immune cell differentiation, activation and development. Altered T cell localization in p110δ-deficient mouse spleen suggested a role for p110δ in non-hematopoietic stromal cells, which maintain hematopoietic cell segregation. We tested this hypothesis using p110δ^WT/WT mouse bone marrow to reconstitute lethally irradiated p110δ^WT/WT or p110δ^D910A/D910A (which express catalytically inactive p110δ) recipients, and studied localization, number and percentage of hematopoietic cell subsets in spleen and lymph nodes, in homeostatic conditions and after antigen stimulation. These analyses showed diffuse T cell areas in p110δ^D910A/D910A and in reconstituted p110δ^D910A/D910A mice in homeostatic conditions. In these mice, spleen CD4⁺ and CD8⁺ T cell numbers did not increase in response to antigen, suggesting that a p110δ^D910A/D910A stroma defect impedes correct T cell response. FACS analysis of spleen stromal cell populations showed a decrease in the percentage of gp38⁻CD31⁺ cells in p110δ^D910A/D910A mice. qRT-PCR studies detected p110δ mRNA expression in p110δ^WT/WT spleen gp38⁻CD31⁺ and gp38⁺CD31⁺ subsets, which was reduced in p110δ^D910A/D910A spleen. Lack of p110δ activity in these cell populations correlated with lower LTβR, CCL19 and CCL21 mRNA levels; these molecules participate in T cell localization to specific spleen areas. Our results could explain the lower T cell numbers and more diffuse T cell areas found in p110δ^D910A/D910A mouse spleen, as well as the lower T cell expansion after antigen stimulation in p110δ^D910A/D910A compared with p110δ^WT/WT mice.     

An Investigation into the Strength of the Association and Agreement Levels between Subjective and Objective Sleep Duration in Adolescents

Study Objectives

The majority of adolescent sleep research has utilized self-reported sleep duration and some have based information on a solitary question. Whilst some have claimed to have validated sleep survey data with objective actigraphy measures in adolescents, the statistical approach applied only demonstrates the strength of the association between subjective and objective sleep duration data and does not reflect if these different methods actually agree.

Methods

Data were collected as part of the Midlands Adolescents Schools Sleep Education Study (MASSES). Adolescents (n=225) aged 11-13 years provided estimates for weekday, weekend and combined sleep duration based on self-reported survey data, a 7-day sleep diary, and wrist-worn actigraphy.

Results

We assessed the strength of the relationship as well as agreement levels between subjective and objectively determined sleep duration (weekday, weekend and combined). Subjective diary sleep duration was significantly correlated with actigraphy estimates for weekday and weekend sleep duration r=0.30, p≤0.001 and r=0.31, p≤0.001 respectively. Pitman’s test demonstrated no significant difference in the variance between weekend sleep duration (r=0.09, p=0.16) and combined sleep duration (r=0.12, p=0.08) indicating acceptable agreement between actigraphy and sleep diary sleep duration only. Self-reported sleep duration estimates (weekday, weekend and combined) did not agree with actigraphy determined sleep duration.

Conclusions

Sleep diaries are a cost-effective alternative to survey/questionnaire data. Self-reported measures of sleep duration in adolescents do not agree with actigraphy measures and should be avoided where possible. Previous adolescent sleep studies that have utilized self-reported survey data may not provide a complete representation of sleep on the outcome measure of interest.     

Hemocyte Density Increases with Developmental Stage in an Immune-Challenged Forest Caterpillar

The cellular arm of the insect immune response is mediated by the activity of hemocytes. While hemocytes have been well-characterized morphologically and functionally in model insects, few studies have characterized the hemocytes of non-model insects. Further, the role of ontogeny in mediating immune response is not well understood in non-model invertebrate systems. The goals of the current study were to (1) determine the effects of caterpillar size (and age) on hemocyte density in naïve caterpillars and caterpillars challenged with non-pathogenic bacteria, and (2) characterize the hemocyte activity and diversity of cell types present in two forest caterpillars: Euclea delphinii and Lithacodes fasciola (Limacodidae). We found that although early and late instar (small and large size, respectively) naïve caterpillars had similar constitutive hemocyte densities in both species, late instar Lithacodes caterpillars injected with non-pathogenic E. coli produced more than a twofold greater density of hemocytes than those in early instars. We also found that both caterpillar species contained plasmatocytes, granulocytes and oenocytoids, all of which are found in other lepidopteran species, but lacked spherulocytes. Granulocytes and plasmatocytes were found to be strongly phagocytic in both species, but granulocytes exhibited a higher phagocytic activity than plasmatocytes. Our results strongly suggest that for at least one measure of immunological response, the production of hemocytes in response to infection, response magnitudes can increase over ontogeny. While the underlying raison d’ être for this improvement remains unclear, these findings may be useful in explaining natural patterns of stage-dependent parasitism and pathogen infection.