ABUNDANCE OF A NOVEL DINOFLAGELLATE PHYLOTYPE IN THE ROSS SEA,ANTARCTICA1

The biodiversity of protistan assemblages present in microhabitats of the Ross Sea, Antarctica, was examined using molecular biological methods to obtain a greater understanding of the genetic diversity present. Sequencing of 18S clone libraries indicated genetically diverse collections of organisms in the water column, ice, and meltwater layer (slush), but a single small subunit ribosomal DNA (srDNA) sequence type dominated clone libraries (>30%) from seawater and slush samples taken within the ice pack of this ecosystem. The BLAST searches indicated that this dominant clone was derived from a dinoflagellate, and that it shared sequence similarity (97.6%–98.3%) with both Karenia and Karlodinium species. Phylogenetic analyses based on small subunit ribosomal gene sequences supported its placement as a sister group to these taxa, and suggested that it represented a novel genus. The dinoflagellate was successfully recovered in culture, and morphological analyses have shown that it contains chloroplasts, is gymnodinoid, appears not to have thecal plates, and has an apical groove and sulcal structure that confirm its placement as a relative of the Karenia/Karlodinium group. The abundance of this phylotype in natural samples was confirmed by quantitative PCR analyses of water and slush communities, and suggests that this dinoflagellate can be a major constituent of the protistan assemblages of some Antarctic microhabitats of the Ross Sea.     

A system to impose prescribed homogenous strains on cultured cells.

There is presently significant interest in cellular responses to physical forces, and numerous devices have been developed to apply stretch to cultured cells. Many of the early devices were limited by the heterogeneity of deformation of cells in different locations and by the high degree of anisotropy at a particular location. We have therefore developed a system to impose cyclic, large-strain, homogeneous stretch on a multiwell surface-treated silicone elastomer substrate plated with pulmonary epithelial cells. The pneumatically driven mechanism consists of four plates each with a clamp to fix one edge of the cruciform elastomer substrate. Four linear bearings set at predetermined angles between the plates ensure a constant ratio of principal strains throughout the stretch cycle. We present the design of the device and membrane shape, the surface modifications of the membrane to promote cell adhesion, predicted and experimental measurements of the strain field, and new data using cultured airway epithelial cells. We present for the first time the relationship between the magnitude of cyclic mechanical strain and the extent of wound closure and cell spreading.     

Characterising the biophysical,economic and social impacts of soil carbon sequestration as a greenhouse gas removal technology

To limit warming to well below 2°C, most scenario projections rely on greenhouse gas removal technologies (GGRTs); one such GGRT uses soil carbon sequestration (SCS) in agricultural land. In addition to their role in mitigating climate change, SCS practices play a role in delivering agroecosystem resilience, climate change adaptability and food security. Environmental heterogeneity and differences in agricultural practices challenge the practical implementation of SCS, and our analysis addresses the associated knowledge gap. Previous assessments have focused on global potentials, but there is a need among policymakers to operationalise SCS. Here, we assess a range of practices already proposed to deliver SCS, and distil these into a subset of specific measures. We provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation of these measures. First, we identify specific practices with potential for both a positive impact on SCS at farm level and an uptake rate compatible with global impact. These focus on: (a) optimising crop primary productivity (e.g. nutrient optimisation, pH management, irrigation); (b) reducing soil disturbance and managing soil physical properties (e.g. improved rotations, minimum till); (c) minimising deliberate removal of C or lateral transport via erosion processes (e.g. support measures, bare fallow reduction); (d) addition of C produced outside the system (e.g. organic manure amendments, biochar addition); (e) provision of additional C inputs within the cropping system (e.g. agroforestry, cover cropping). We then consider economic and non‐cost barriers and incentives for land managers implementing these measures, along with the potential externalised impacts of implementation. This offers a framework and reference point for holistic assessment of the impacts of SCS. Finally, we summarise and discuss the ability of extant scientific approaches to quantify the technical potential and externalities of SCS measures, and the barriers and incentives to their implementation in global agricultural systems.     

钼酸盐转运体ModABC促进肺炎克雷伯菌肌肉感染及其治疗新思路

【背景】肺炎克雷伯菌(肺克)是医院感染和社区获得性感染的重要病原菌,由于近年来肺克菌株耐药情况越来越严重,使得其感染在临床治疗上更加棘手。目前肺克感染引起化脓性肌炎的罕见病例越来越多,而深层肌肉组织感染可能会形成厌氧环境,钼酸盐转运体ModABC是细菌厌氧硝酸盐呼吸所必需。前期研究发现ModA可能与肺克毒力正相关。【目的】研究钼酸盐转运体ModABC对肺克肌肉感染的作用及钨酸盐治疗的可能性。【方法】构建modA无痕缺失突变株与回补株,通过检测体外厌氧生长、硝酸还原酶活性和小鼠肌肉感染实验分析ModABC对肺克肌肉感染的作用及机制;通过钨酸盐处理(体外、体内)探讨钨酸盐治疗肺克肌肉感染的可能性及疗效。【结果】成功构建了modA无痕缺失突变株与回补株,发现modA基因敲除后肺克体外厌氧生长明显被极大地抑制、硝酸还原酶活性显著降低,小鼠肌肉脓肿模型显示敲除株ΔmodA感染肌肉脓肿大大消减,并且在肌内生长及侵袭受限;体外钨酸盐处理能够抑制野生株WT厌氧硝酸盐呼吸,在肌肉脓肿模型中也能显著抑制WT生长,但对敲除株ΔmodA无影响。【结论】钼酸盐转运体ModABC通过增强侵袭力和促进厌氧硝酸盐呼吸来提供适应优势而促进肺克肌肉感染,钨酸盐可以降低由ModA赋予的适应优势而对肺克肌肉感染具有一定的治疗作用。本研究有助于阐明钼离子对肺克致病性的作用机制及为其治疗提供新思路,为深入研究肺克尤其是耐碳青霉烯高毒力肺克感染的治疗奠定基础。     

1H, 15N and 13C chemical shifts of the D. melanogaster myosin VI light chain androcam in high calcium

Androcam is a calmodulin-like protein that acts as a testis-specific light chain to myosin VI during spermatogenesis in D. melanogaster. Modest, localized chemical shift changes that accompany Ca²⁺ binding to the androcam N-terminal lobe indicate that unlike calmodulin, androcam does not undergo a dramatic conformational change upon binding calcium. Here we report the ¹H, ¹⁵N and ¹³C resonances of androcam in the high calcium (10 mM) state and show the extent of chemical shift changes for backbone resonances relative to the low calcium state.     

Pregnancy-Specific Glycoproteins Bind Integrin αIIbβ3 and Inhibit the Platelet—Fibrinogen Interaction

Pregnancy-specific glycoproteins (PSGs) are immunoglobulin superfamily members encoded by multigene families in rodents and primates. In human pregnancy, PSGs are secreted by the syncytiotrophoblast, a fetal tissue, and reach a concentration of up to 400 ug/ml in the maternal bloodstream at term. Human and mouse PSGs induce release of anti-inflammatory cytokines such as IL-10 and TGFβ1 from monocytes, macrophages, and other cell types, suggesting an immunoregulatory function. RGD tri-peptide motifs in the majority of human PSGs suggest that they may function like snake venom disintegrins, which bind integrins and inhibit interactions with ligands. We noted that human PSG1 has a KGD, rather than an RGD motif. The presence of a KGD in barbourin, a platelet integrin αIIbβ3 antagonist found in snake venom, suggested that PSG1 may be a selective αIIbβ3 ligand. Here we show that human PSG1 binds αIIbβ3 and inhibits the platelet – fibrinogen interaction. Unexpectedly, however, the KGD is not critical as multiple PSG1 domains independently bind and inhibit αIIbβ3 function. Human PSG9 and mouse Psg23 are also inhibitory suggesting conservation of this function across primate and rodent PSG families. Our results suggest that in species with haemochorial placentation, in which maternal blood is in direct contact with fetal trophoblast, the high expression level of PSGs reflects a requirement to antagonise abundant (3 mg/ml) fibrinogen in the maternal circulation, which may be necessary to prevent platelet aggregation and thrombosis in the prothrombotic maternal environment of pregnancy.     

Mannitol Utilisation is Required for Protection of Staphylococcus aureus from Human Skin Antimicrobial Fatty Acids

Mannitol (Mtl) fermentation, with the subsequent production of acid, is a species signature of Staphylococcus aureus, and discriminates it from most other members of the genus. Inactivation of the gene mtlD, encoding Mtl-1-P dehydrogenase was found to markedly reduce survival in the presence of the antimicrobial fatty acid, linoleic acid. We demonstrate that the sugar alcohol has a potentiating action for this membrane-acting antimicrobial. Analysis of cellular metabolites revealed that, during exponential growth, the mtlD mutant accumulated high levels of Mtl and Mtl-P. The latter metabolite was not detected in its isogenic parent strain or a deletion mutant of the entire mtlABFD operon. In addition, the mtlD mutant strain exhibited a decreased MIC for H₂O₂, however virulence was unaffected in a model of septic arthritis.