Hexasaturnalis nakasekoi nov. sp., a Jurassic saturnalid radiolarian species frequently confounded with Hexasaturnalis suboblongus (Yao)

Detailed morphological study of the ring of the Jurassic saturnalid radiolarian species frequently cited in the literature as Hexasaturnalis suboblongus (Yao) has proven that it contains two well-defined species: H. suboblongus (Yao), practically ranging within the boundaries of the Bajocian, and Hexasaturnalis nakasekoi nov. sp., ranging within the Bathonian-Kimmeridgian interval. The two species seem to be important stratigraphically because the transition from the former to the latter took place at or around the Bajocian/Bathonian boundary. The phyletic lineage Hexasaturnalis hexagonus (Yao) → H. inuyamaensis (Yao) → H. suboblongus (Yao) → H. nakasekoi nov. sp. → H. minor (Baumgartner) → Dicerosaturnalis angustus (Baumgartner) → D. dicranacanthos (Squinabol) is proposed.     

The potential effect of sustained hypoxia on nitrogen cycling in sediment from the southern North Sea: a mesocosm experiment

The potential effect of sustained hypoxia (up to 70 days) on the production of N₂ gas through denitrification and anammox, as well as sediment–water exchange of nitrite, nitrate and ammonia, oxygen consumption and penetration, were measured in mesocosms using sediment collected from the southern North Sea (north of Dogger Bank). As expected, both the penetration of oxygen into, and consumption of oxygen by, the sediment decreased by 42 and 46 %, respectively, once hypoxia was established. Importantly, the oxygen regime did not change significantly (P > 0.05) during the experiment, suggesting that organic carbon was not depleted. During the first 10 days, the exchange of NO₃ ^?, NO₂ ^? and NH₄ ⁺ between the sediment and water was erratic but once a steady state was established the sediment acted as either a sink for fixed nitrogen under hypoxia or as a source in the controls. Over the course of the mesocosm experiment the rate of both anammox and denitrification increased, with anammox increasing disproportionately under hypoxia relative to the controls, whereas the rate of increase in denitrification was the same for both. Under sustained hypoxia the production of N₂ gas increased by 72 % relative to the controls, with this increase in N₂ production remaining constant regardless of the duration of hypoxia. Longer periods of stratification and oxygen depletion are predicted to occur more regularly in the bottom waters of shallow coastal seas as one manifestation of climate change. Under sustained hypoxia the potential for nitrogen removal by the production of N₂ gas in this region of the southern North Sea was estimated to increase from 2.1 kt N 150 days^?1 to 3.6 kt 150 days^?1, while the efflux of dissolved inorganic nitrogen ceased altogether; both of which could down regulate the productivity of this region as a whole.     

Potassium deficiency triggers the development of dormant cells (akinetes) in Aphanizomenon ovalisporum (Nostocales,Cyanoprokaryota)1

Akinetes are spore‐like nonmotile cells that differentiate from vegetative cells of filamentous cyanobacteria from the order Nostocales. They play a key role in the survival and distribution of these species and contribute to their perennial blooms. Various environmental factors were reported to trigger the differentiation of akinetes including light intensity and quality, temperature, and nutrient deficiency. Here, we report that deprivation of potassium ion (K⁺) triggers akinete development in the cyanobacterium Aphanizomenon ovalisporum. Akinetes formation is initiated 3 d–7 d after an induction by K⁺ depletion, followed by 2–3 weeks of a maturation process. Akinete formation occurs within a restricted matrix of environmental conditions such as temperature, light intensity or photon flux. Phosphate is essential for akinete maturation and P‐limitation restricts the number of mature akinetes. DNA replication is essential for akinete maturation and akinete development is limited in the presence of Nalidixic acid. While our results unequivocally demonstrated the effect of K⁺ deficiency on akinete formation in laboratory cultures of A. ovalisporum, this trigger did not cause Cylindrospermopsis raciborskii to produce akinetes. Anabaena crassa however, produced akinetes upon potassium deficiency, but the highest akinete concentration was achieved at conditions that supported vegetative growth. It is speculated that an unknown internal signal is associated with the cellular response to K⁺ deficiency to induce the differentiation of a certain vegetative cell in a trichome into an akinete. A universal stress protein that functions as mediator in K⁺ deficiency signal transduction cascade, may communicate between the lack of K⁺ and akinete induction.     

Sequence Analysis of In Vivo Defective Interfering-Like RNA of Influenza A H1N1 Pandemic Virus

Influenza virus defective interfering (DI) particles are naturally occurring noninfectious virions typically generated during in vitro serial passages in cell culture of the virus at a high multiplicity of infection. DI particles are recognized for the role they play in inhibiting viral replication and for the impact they have on the production of infectious virions. To date, influenza virus DI particles have been reported primarily as a phenomenon of cell culture and in experimentally infected embryonated chicken eggs. They have also been isolated from a respiratory infection of chickens. Using a sequencing approach, we characterize several subgenomic viral RNAs from human nasopharyngeal specimens infected with the influenza A(H1N1)pdm09 virus. The distribution of these in vivo-derived DI-like RNAs was similar to that of in vitro DIs, with the majority of the defective RNAs generated from the PB2 (segment 1) of the polymerase complex, followed by PB1 and PA. The lengths of the in vivo-derived DI-like segments also are similar to those of known in vitro DIs, and the in vivo-derived DI-like segments share internal deletions of the same segments. The presence of identical DI-like RNAs in patients linked by direct contact is compatible with transmission between them. The functional role of DI-like RNAs in natural infections remains to be established.     

Rab and ARF GTPase regulation of exocytosis (Review)

Our understanding of the mechanisms governing of Rab and Arf protein function has exploded in recent years with a convergence of information from model genetic organisms, biochemical studies, cell biological observations and protein structural information. However, the list of known Rab and Arf interacting factors still remains small relative to the number of these small GTPases that have been identified through complete genomic sequencing. It can be anticipated that the factors listed and discussed in this review probably represent a small fraction of the Rab and Arf accessory molecules that remain to be discovered. The identification of regulators and accessory molecules for the Rab and Arf families has allowed investigators to elaborate themes and develop a framework for a mechanistic understanding of these proteins. The themes are highlighted in this review, which aims to concentrate on Rab and Arf function in exocytosis.     

Carnosine: from exercise performance to health

Carnosine was first discovered in skeletal muscle, where its concentration is higher than in any other tissue. This, along with an understanding of its role as an intracellular pH buffer has made it a dipeptide of interest for the athletic population with its potential to increase high-intensity exercise performance and capacity. The ability to increase muscle carnosine levels via β-alanine supplementation has spawned a new area of research into its use as an ergogenic aid. The current evidence base relating to the use of β-alanine as an ergogenic aid is reviewed here, alongside our current thoughts on the potential mechanism(s) to support any effect. There is also some emerging evidence for a potential therapeutic role for carnosine, with this potential being, at least theoretically, shown in ageing, neurological diseases, diabetes and cancer. The currently available evidence to support this potential therapeutic role is also reviewed here, as are the potential limitations of its use for these purposes, which mainly focusses on issues surrounding carnosine bioavailability.     

Mechanism of Membrane Permeation Induced by Synthetic β-Hairpin Peptides

We have investigated the membrane destabilizing properties of synthetic amphiphilic cationic peptides, MAX1 and MAX35, which have the propensity to form β-hairpin structures under certain conditions, and a control non-β-hairpin-forming peptide MAX8V16E. All three peptides bind to liposomes containing a mixture of zwitterionic POPC and negatively charged POPS lipids as determined by Zeta potential measurements. Circular dichroism measurements indicated folding of MAX1 and MAX35 in the presence of the POPC/POPS liposomes, whereas no such folding was observed with MAX8V16E. There was no binding or folding of these peptides to liposomes containing only POPC. MAX1 and MAX35 induced release of contents from negatively charged liposomes, whereas MAX8V16E failed to promote solute release under identical conditions. Thus, MAX1 and MAX35 bind to, and fold at the surface of negatively charged liposomes adopting a lytic conformation. We ruled out leaky fusion as a mechanism of release by including 2 mol % PEG-PE in the liposomes, which inhibits aggregation/fusion but not folding of MAX or MAX-induced leakage. Using a concentration-dependent quenching probe (calcein), we determined that MAX-induced leakage of liposome contents was an all-or-none process. At MAX1 concentrations, which cause release of ∼50% of the liposomes that contain small (R_h <1.5 nm) markers, only ∼15% of those liposomes release a fluorescent dextran of 40 kDa. A multimeric model of the pore is presented based on these results. Atomistic molecular dynamics simulations show that barrels consisting of 10 β-hairpin MAX1 and MAX35 peptides are relatively more stable than MAX8V16E barrels in the bilayer, suggesting that barrels of this size are responsible for the peptides lytic action.     

Assessing the Response of Nematode Communities to Climate Change-Driven Warming: A Microcosm Experiment

Biodiversity has diminished over the past decades with climate change being among the main responsible factors. One consequence of climate change is the increase in sea surface temperature, which, together with long exposure periods in intertidal areas, may exceed the tolerance level of benthic organisms. Benthic communities may suffer structural changes due to the loss of species or functional groups, putting ecological services at risk. In sandy beaches, free-living marine nematodes usually are the most abundant and diverse group of intertidal meiofauna, playing an important role in the benthic food web. While apparently many functionally similar nematode species co-exist temporally and spatially, experimental results on selected bacterivore species suggest no functional overlap, but rather an idiosyncratic contribution to ecosystem functioning. However, we hypothesize that functional redundancy is more likely to observe when taking into account the entire diversity of natural assemblages. We conducted a microcosm experiment with two natural communities to assess their stress response to elevated temperature. The two communities differed in diversity (high [HD] vs. low [LD]) and environmental origin (harsh vs. moderate conditions). We assessed their stress resistance to the experimental treatment in terms of species and diversity changes, and their function in terms of abundance, biomass, and trophic diversity. According to the Insurance Hypothesis, we hypothesized that the HD community would cope better with the stressful treatment due to species functional overlap, whereas the LD community functioning would benefit from species better adapted to harsh conditions. Our results indicate no evidence of functional redundancy in the studied nematofaunal communities. The species loss was more prominent and size specific in the HD; large predators and omnivores were lost, which may have important consequences for the benthic food web. Yet, we found evidence for alternative diversity–ecosystem functioning relationships, such as the Rivets and the Idiosyncrasy Model.