Photosystem II Peripheral Accessory Chlorophyll Mutants in Chlamydomonas reinhardtii. Biochemical Characterization and Sensitivity to Photo-Inhibition

In addition to the four chlorophylls (Chls) involved in primary charge separation, the photosystem II (PSII) reaction center polypeptides, D1 and D2, coordinate a pair of symmetry-related, peripheral accessory Chls. These Chls are axially coordinated by the D1-H118 and D2-H117 residues and are in close association with the proximal Chl antennae proteins, CP43 and CP47. To gain insight into the function(s) of each of the peripheral Chls, we generated site-specific mutations of the amino acid residues that coordinate these Chls and characterized their energy and electron transfer properties. Our results demonstrate that D1-H118 and D2-H117 mutants differ with respect to: (a) their relative numbers of functional PSII complexes, (b) their relative ability to stabilize charge-separated states, (c) light-harvesting efficiency, and (d) their sensitivity to photo-inhibition. The D2-H117N and D2-H117Q mutants had reduced levels of functional PSII complexes and oxygen evolution capacity as well as reduced light-harvesting efficiencies relative to wild-type cells. In contrast, the D1-H118Q mutant was capable of near wild-type rates of oxygen evolution at saturating light intensities. The D1-H118Q mutant also was substantially more resistant to photo-inhibition than wild type. This reduced sensitivity to photo-inhibition is presumably associated with a reduced light-harvesting efficiency in this mutant. Finally, it is noted that the PSII peripheral accessory Chls have similarities to a to a pair of Chls also present in the PSI reaction center complex

The \u27Pseudomonas aeruginosa\u27 PSL Polysaccharide Is a Social but Noncheatable Trait in Biofilms

Extracellular polysaccharides are compounds secreted by microorganisms into the surrounding environment, and they are important for surface attachment and maintaining structural integrity within biofilms. The social nature of many extracellular polysaccharides remains unclear, and it has been suggested that they could function as either cooperative public goods or as traits that provide a competitive advantage. Here, we empirically tested the cooperative nature of the PSL polysaccharide, which is crucial for the formation of biofilms in Pseudomonas aeruginosa. We show that (i) PSL is not metabolically costly to produce; (ii) PSL provides populationlevel benefits in biofilms, for both growth and antibiotic tolerance; (iii) the benefits of PSL production are social and are shared with other cells; (iv) the benefits of PSL production appear to be preferentially directed toward cells which produce PSL; (v) cells which do not produce PSL are unable to successfully exploit cells which produce PSL. Taken together, this suggests that PSL is a social but relatively nonexploitable trait and that growth within biofilms selects for PSL-producing strains, even when multiple strains are on a patch (low relatedness at the patch level)

Continental threat: How many common carp (Cyprinus carpio) are there in Australia?

Common carp (Cyprinus carpio) are one of the world's most destructive vertebrate pests. In Australia, they dominate many aquatic ecosystems causing a severe threat to aquatic plants, invertebrates, water quality, native fish and social amenity. The Australian Government is considering release of cyprinid herpesvirus-3 (CyHV-3) as a control measure and consequently a robust, continental-scale estimate of the carp population and biomass is essential to inform planning and risk management. Here, we pioneer a novel model-based approach to provide the first estimate of carp density (no/ha) and biomass density (kg/ha) at river reach/waterbody, basin and continental scales. We built a spatial layer of rivers and waterbodies, classified aquatic habitats and calculated the area of each throughout the range of carp in Australia. We then developed a database of fishery-independent electrofishing catch-per-unit-effort (CPUE) for habitat types, containing catch information for 574,145 carp caught at 4831 sites. Eastern Australia accounted for 96% of carp biomass and 92% of the total available wetted habitat area (16,686 km2) was occupied. To correct these data for variable detection efficiencies, we used existing electrofishing data and undertook additional field experiments to establish relationships between relative and absolute abundances. We then scaled-up site-based estimates to habitat types to generate continental estimates. The number of carp was estimated at 199.2 M (95%Crl: 106 M to 357.6 M) for an ‘average’ hydrological scenario and 357.5 M (95%Crl: 178.9 M to 685.1 M) for a ‘wet’ hydrological scenario. In eastern Australia, these numbers correspond with biomasses of 205,774 t (95%Crl: 117,532–356,482 t) (average scenario) and 368,357 t (95%Crl: 184,234–705,630 t) (wet scenario). At a continental scale the total biomass was estimated at 215,456 t for an ‘average’ hydrological scenario. Perennial lowland rivers had the highest CPUE and greatest biomass density (up to 826 kg/ha) and the modelled biomass exceeded a density-impact threshold of 80–100 kg/ha in 54% of wetlands and 97% of stream area in large lowland rivers. The continental-scale biomass estimates provide a baseline for focusing national conservation strategies to reduce carp populations below thresholds needed to restore aquatic ecosystems at a range of spatial scales

AORTIC DISSECTION IN THE ELDERLY: COMPARING SEPTUAGENARIANS AND OCTOGENARIANS

none15siopenJabara, Justin; Peterson, Mark; Trimarchi, Santi; Myrmel, Truls; Reece, T. Brett; Bossone, Eduardo; Hutchison, Stuart; Gilon, Dan; Appoo, Jehangir; Di Eusanio, Marco; Montgomery, Daniel; Isselbacher, Eric; Nienaber, Christoph; Eagle, Kim; Patel, HimanshuJabara, Justin; Peterson, Mark; Trimarchi, Santi; Myrmel, Truls; Reece, T. Brett; Bossone, Eduardo; Hutchison, Stuart; Gilon, Dan; Appoo, Jehangir; Di Eusanio, Marco; Montgomery, Daniel; Isselbacher, Eric; Nienaber, Christoph; Eagle, Kim; Patel, Himansh

Bell Beaker people in Britain: migration, mobility and diet

The appearance of the distinctive ‘Beaker package’ marks an important horizon in British prehistory, but was it associated with immigrants to Britain or with indigenous converts? Analysis of the skeletal remains of 264 individuals from the British Chalcolithic–Early Bronze Age is revealing new information about the diet, migration and mobility of those buried with Beaker pottery and related material. Results indicate a considerable degree of mobility between childhood and death, but mostly within Britain rather than from Europe. Both migration and emulation appear to have had an important role in the adoption and spread of the Beaker package

CHRONOBIOLOGICAL PATTERNS OF ACUTE AORTIC DISSECTION IN MARFAN SYNDROME PATIENTS: DATA FROM THE INTERNATIONAL REGISTRY OF ACUTE AORTIC DISSECTION (IRAD)

none17siopenSiddiqi, Hasan; Lindsay, Mark; Di Eusanio, Marco; Hutchison, Stuart; Braverman, Alan; Peterson, Mark; Gleason, Thomas; Sechtem, Udo; Myrmel, Truls; Bossone, Eduardo; Montgomery, Daniel; Manfredini, Roberto; Gilon, Dan; Nienaber, Christoph; Eagle, Kim; Isselbacher, Eric; Pyeritz, ReedSiddiqi, Hasan; Lindsay, Mark; Di Eusanio, Marco; Hutchison, Stuart; Braverman, Alan; Peterson, Mark; Gleason, Thomas; Sechtem, Udo; Myrmel, Truls; Bossone, Eduardo; Montgomery, Daniel; Manfredini, Roberto; Gilon, Dan; Nienaber, Christoph; Eagle, Kim; Isselbacher, Eric; Pyeritz, Ree

Thymus transplantation for complete DiGeorge syndrome: European experience

Background: Thymus transplantation is a promising strategy for the treatment of athymic complete DiGeorge syndrome (cDGS). Methods: Twelve patients with cDGS were transplanted with allogeneic cultured thymus. Objective: To confirm and extend the results previously obtained in a single centre. Results: Two patients died of pre-existing viral infections without developing thymopoeisis and one late death occurred from autoimmune thrombocytopaenia. One infant suffered septic shock shortly after transplant resulting in graft loss and the need for a second transplant. Evidence of thymopoeisis developed from 5-6 months after transplantation in ten patients. The median (range) of circulating naïve CD4 counts (x10663 /L) were 44(11-440) and 200(5-310) at twelve and twenty-four months post-transplant and T-cell receptor excision circles were 2238 (320-8807) and 4184 (1582 -24596) per106 65 T-cells. Counts did not usually reach normal levels for age but patients were able to clear pre-existing and later acquired infections. At a median of 49 months (22-80), eight have ceased prophylactic antimicrobials and five immunoglobulin replacement. Histological confirmation of thymopoeisis was seen in seven of eleven patients undergoing biopsy of transplanted tissue including five showing full maturation through to the terminal stage of Hassall body formation. Autoimmune regulator (AIRE) expression was also demonstrated. Autoimmune complications were seen in 7/12 patients. In two, early transient autoimmune haemolysis settled after treatment and did not recur. The other five suffered ongoing autoimmune problems including: thyroiditis (3); haemolysis (1), thrombocytopaenia (4) and neutropenia (1). Conclusions: This study confirms the previous reports that thymus transplantation can reconstitute T cells in cDGS but with frequent autoimmune complications in survivors