Cultivation of Walsby's square haloarchaeon

The square haloarchaea of Walsby (SHOW group) dominate hypersaline microbial communities but have not been cultured since their discovery 25 years ago. We show that natural water dilution cultures can be used to isolate members of this group and, once in pure culture, they can be grown in standard halobacterial media. Cells display a square morphology and contain gas vesicles and poly-beta-hydroxybutyrate (PHB) granules. The 16S rRNA gene sequence was >99% identical to other SHOW group sequences. They prefer high salinities (23-30%), and can grow with a doubling time of 1-2 days in rich media. The ability to culture SHOW group organisms makes it possible to study, in a comprehensive way, the microbial ecology of salt lakes.     

Xanthones from a microfungus of the genus Xylaria

Chemical investigations of a microfungus Xylaria sp. isolated from the Australian rainforest tree Glochidion ferdinandi have afforded two new natural products, 2-hydroxy-6-methyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid (1) and 2-hydroxy-6-hydroxymethyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid (2). Compound 1 has previously been synthesised but only partially characterised. Methylation of 1 using diazomethane afforded the crystalline compound 2,8-dimethoxy-6-methyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ester (3), whose structure was determined by single crystal X-ray analysis. This paper reports the full spectroscopic characterisation of compounds 1-3 by NMR, UV, IR and MS data. All compounds were inactive in a brine shrimp lethality assay and several antimicrobial screens.     

Plant sensitivity to low intensity 105 GHz electromagnetic radiation

Exposing seedlings of the flax, Linum usitatissimum L., to a variety of weak environmental stresses followed by a 2 day calcium deprivation, triggers the common response of production of epidermal meristems (actively dividing groups of cells) in the hypocotyl, which is the part of the stem between the root and the cotyledons (the pre-existing leaves in the embryo). This production reaches a plateau of 10-20 meristems after a month in the case of mechanical stimulation and cold shock. Recently, we have shown that radiation from a global system for mobile communication (GSM) telephone also triggers production of meristems with a plateau of around six meristems. Here, we show that a single 2 h exposure to radiation emitted at 105 GHz at non-thermal levels by a Gunn oscillator induces meristem production with kinetics similar to that induced by weak environmental stimuli and radiation from GSM telephone.     

Differential tolerance of body fluid dilution in two species of tropical hermit crabs: not due to osmotic/ionic regulation

The tropical intertidal hermit crabs Clibanarius taeniatus and Clibanarius virescens were examined for differences in survival and physiological responses in low salinity. We found that C. taeniatus survived better in dilute seawater than C. virescens and that these species did not differ in their abilities to regulate haemolymph osmolarity, ionic concentration of the haemolymph or body fluid volume. We also found no difference in oxygen consumption between the species when acutely exposed to a range of temperature and salinity combinations. It is concluded that the greater survival in dilute seawater by C. taeniatus compared to C. virescens is due to a greater tolerance of dilution of body fluids by C. taeniatus. Differences in tolerance to dilute seawater may influence the habitat preferences of these species within the same geographical area.     

Structure of biological solar energy converters - further revelations

Photosynthetic organisms harvest solar energy by absorbing light and ultimately transferring energy through a cascade of chemical reactions to power all cellular processes. Core components initiating this reaction cascade are the photosynthetic reaction centres Photosystem I and Photosystem II. Two recent publications on the structure of the reaction centres by Adam Ben-Shem et al. and Kristina Ferreira et al. represent a big step towards understanding the evolutionary development of the core energy conversion process and identifying the site of the water oxidation process, the source of atmospheric oxygen.     

Public, private and non-specific antibodies induced by non-cytopathic viral infections

Lymphocytic choriomeningitis virus (LCMV) represents a useful experimental model of murine infection with a non-cytopathic virus, bearing resemblance to HIV and hepatitis C virus (HCV) infections in humans. Recent data from the LCMV model indicate that the humoral immune response that is induced by non-cytopathic viruses is far more complex than previously appreciated. LCMV-induced IgG production is largely polyclonal, with more than 90% of the antibody repertoire constituting non-relevant specificities. A delayed virus-neutralizing antibody response is induced, including specificities directed not only against the parental LCMV-strain present in the host but also cross-specifically against LCMV-variants isolated from other hosts. These findings provide novel insights to aid our understanding of clinically relevant observations that are recorded following human infection with HIV, HCV and dengue viruses.     

Missorting of LaCrosse virus nucleocapsid protein by the interferon-induced MxA GTPase involves smooth ER membranes

The interferon-induced human MxA protein belongs to the class of dynamin-like, large guanosine-5'-triphosphatases that are involved in intracellular vesicle trafficking and organelle homeostasis. MxA shares many properties with the other members of this protein superfamily, including the propensity to self-assemble and to associate with lipid membranes. However, MxA is unique in that it has antiviral activity and inhibits the replication of several RNA viruses. Here, we determined the role of membranes for the antiviral function of MxA using LaCrosse-bunyavirus (LACV). We show that MxA does not affect trafficking and sorting of viral glycoproteins but binds and mislocates the viral nucleocapsid (N) protein into membrane-associated, large perinuclear complexes. We further demonstrate that MxA localizes to a subcompartment of the smooth endoplasmic reticulum where the viral N protein accumulates. In infected MxA-expressing cells, oligomeric MxA/N complexes are formed in close association with COP-I-positive vesicular-tubular membranes. Our results suggest that this membrane compartment is the preferred place where MxA and N interact, leading to efficient sequestration and missorting of an essential viral component.     

Southern Sea Otter as a Sentinel of Marine Ecosystem Health

The southern sea otter (Enhydra lutris nereis) is listed as threatened under the Endangered Species Act (ESA) and is a keystone species, strongly influencing the abundance and diversity of the other species within its kelp forest ecosystem. This is accomplished primarily by preying upon urchins that eat the kelp stipe and holdfast, which can reduce a kelp forest to an urchin barren. Sea otters are very susceptible to marine pollutants such as petroleum, which may be directly toxic and/or alter their furs insulating properties. Sea otters are an excellent sentinel species. They eat approximately 25% of their body weight per day in shellfish and other invertebrates, and can concentrate and integrate chemical contaminants. In addition, they appear to be susceptible to a number of diseases and parasites that may have anthropogenic origins, and shellfish may serve as an intermediary for some of these infections. Many of the shellfish the otters eat are also harvested for human food. In their role as sentinels, sea otter health has implications for human health, economic sustainability of shellfisheries, as well as overall marine ecosystem health. The recent southern sea otter decline has been viewed with some alarm by conservationists and, indeed, recovery seems a long way off. High mortality rather than depressed recruitment appears to underlie the decline. A good deal of debate has centered on the role of infectious diseases and parasites, exposure to contaminants, nutrition and prey availability, net and pot fishery interactions, and other sources of mortality. Current research is being done related to major classes of mortality, various types of pollutants and some specific organisms causing southern sea otter mortality, and their implications for marine ecosystem health and sustainability.