When continents break apart, the rifting is sometimes accompanied by the production of large volumes of molten rock. The total melt volume, however, is uncertain, because only part of it has erupted at the surface. Furthermore, the cause of the magmatism is still disputed-specifically, whether or not it is due to increased mantle temperatures. We recorded deep-penetration normal-incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the northeast Atlantic. Here we show that near the Faroe Islands, for every 1 km along strike, 360-400 km(3) of basalt is extruded, while 540-600 km(3) is intruded into the continent-ocean transition. We find that lower-crustal intrusions are focused mainly into a narrow zone approximately 50 km wide on the transition, although extruded basalts flow more than 100 km from the rift. Seismic profiles show that the melt is intruded into the lower crust as sills, which cross-cut the continental fabric, rather than as an 'underplate' of 100 per cent melt, as has often been assumed. Evidence from the measured seismic velocities and from igneous thicknesses are consistent with the dominant control on melt production being increased mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or the presence of fertile mantle at the time of continental break-up, as has previously been suggested for the North Atlantic Ocean.

Aims: Protein S-bacillithiolations are mixed disulfides between protein thiols and the bacillithiol (BSH) redox buffer that occur in response to NaOCl in Bacillus subtilis. We used BSH-specific immunoblots, shotgun liquid chromatography (LC)-tandem mass spectrometry (MS/MS) analysis and redox proteomics to characterize the Sbacillithiolomes of B. subtilis, B. megaterium, B. pumilus, B. amyloliquefaciens, and Staphylococcus carnosus and also measured the BSH/oxidized bacillithiol disulfide (BSSB) redox ratio after NaOCl stress. Results: In total, 54 proteins with characteristic S-bacillithiolation (SSB) sites were identified, including 29 unique proteins and eight proteins conserved in two or more of these bacteria. The methionine synthase MetE is the most abundant Sbacillithiolated protein in Bacillus species after NaOCl exposure. Further, S-bacillithiolated proteins include the translation elongation factor EF-Tu and aminoacyl-tRNA synthetases (ThrS), the DnaK and GrpE chaperones, the two-Cys peroxiredoxin YkuU, the ferredoxin-NADP + oxidoreductase YumC, the inorganic pyrophosphatase PpaC, the inosine-5¢-monophosphate dehydrogenase GuaB, proteins involved in thiamine biosynthesis (ThiG and ThiM), queuosine biosynthesis (QueF), biosynthesis of aromatic amino acids (AroA and AroE), serine (SerA), branched-chain amino acids (YwaA), and homocysteine (LuxS and MetI). The thioredoxin-like proteins, YphP and YtxJ, are S-bacillithiolated at their active sites, suggesting a function in the de-bacillithiolation process. Sbacillithiolation is accompanied by a two-fold increase in the BSSB level and a decrease in the BSH/BSSB redox ratio in B. subtilis. Innovation: Many essential and conserved proteins, including the dominant MetE, were identified in the S-bacillithiolome of different Bacillus species and S. carnosus using shotgun-LC-MS/MS analyses. Conclusion: S-bacillithiolation is a widespread redox control mechanism among Firmicutes bacteria that protects conserved metabolic enzymes and essential proteins against overoxidation.

S U M M A R YWe present a 3-D joint inversion framework for seismic, magnetotelluric (MT) and scalar and tensorial gravity data. Using large-scale optimization methods, parallel forward solvers and a flexible implementation in terms of model parametrization allows us to investigate different coupling approaches for the various physical parameters involved in the joint inversion. Here we compare two different coupling approaches, direct parameter coupling where we calculate conductivities and densities from seismic slownesses and cross-gradient coupling, where each model cell has an independent value for each physical property and a structural similarity is enforced through a term in the objective function.For both types of approaches we see an improvement of the inversion results over single inversions when the inverted data sets are generated from compatible models. As expected the direct coupling approach results in a stronger interaction between the data sets and in this case better results compared to the cross-gradient coupling. In contrast, when the inverted MT data is generated from a model that violates the parameter relationship in some regions but conforms with the cross-gradient assumptions, we obtain good results with the cross-gradient approach, while the direct coupling approach results in spurious features. This makes the cross-gradient approach the first choice for regions were a direct relationship between the physical parameters is unclear.

FosB is a divalent-metal-dependent thiol-S-transferase implicated in fosfomycin resistance among many pathogenic Gram-positive bacteria. In the present paper, we describe detailed kinetic studies of FosB from Staphylococcus aureus (SaFosB) that confirm that bacillithiol (BSH) is its preferred physiological thiol substrate. SaFosB is the first to be characterized among a new class of enzyme (bacillithiol-S-transferases), which, unlike glutathione transferases, are distributed among many low-G + C Gram-positive bacteria that use BSH instead of glutathione as their major low-molecular-mass thiol. The Km values for BSH and fosfomycin are 4.2 and 17.8 mM respectively. Substrate specificity assays revealed that the thiol and amino groups of BSH are essential for activity, whereas malate is important for SaFosB recognition and catalytic efficiency. Metal activity assays indicated that Mn2+ and Mg2+ are likely to be the relevant cofactors under physiological conditions. The serine analogue of BSH (BOH) is an effective competitive inhibitor of SaFosB with respect to BSH, but uncompetitive with respect to fosfomycin. Coupled with NMR characterization of the reaction product (BS– fosfomycin), this demonstrates that the SaFosB-catalysed reaction pathway involves a compulsory ordered binding mechanism with fosfomycin binding first followed by BSH which then attacks the more sterically hindered C-1 carbon of the fosfomycin epoxide. Disruption of BSH biosynthesis in S. aureus increases sensitivity to fosfomycin. Together, these results indicate that SaFosB is a divalent-metal-dependent bacillithiol-S-transferase that confers fosfomycin resistance on S. aureus.

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Herbarium specimens provide verifiable and citable evidence of the occurrence of particular plants at particular points in space and time, and are vital resources for assessing extinction risk in the tropics, where plant diversity and threats to plants are greatest. We reviewed approaches to assessing extinction risk in response to the Convention on Biological Diversity's Global Strategy for Plant Conservation Target 2: an assessment of the conservation status of all known plant species by 2020. We tested five alternative approaches, using herbarium-derived data for trees, shrubs and herbs in five different plant groups from temperate and tropical regions. All species were previously fully assessed for the IUCN Red List. We found significant variation in the accuracy with which different approaches classified species as threatened or not threatened. Accuracy was highest for the machine learning model (90%) but the least data-intensive approach also performed well (82%). Despite concerns about spatial, temporal and taxonomic biases and uncertainties in herbarium data, when specimens represent the best available evidence for particular species, their use as a basis for extinction risk assessment is appropriate, necessary and urgent. Resourcing herbaria to maintain, increase and disseminate their specimen data is essential to guide and focus conservation action.This article is part of the theme issue ‘Biological collections for understanding biodiversity in the Anthropocene’.

In Staphylococcus aureus, the low-molecular-weight thiol called bacillithiol (BSH), together with cognate S-transferases, is believed to be the counterpart to the glutathione system of other organisms. To explore the physiological role of BSH in S. aureus, we constructed mutants with the deletion of bshA (sa1291), which encodes the glycosyltransferase that catalyzes the first step of BSH biosynthesis, and fosB (sa2124), which encodes a BSH-S-transferase that confers fosfomycin resistance, in several S. aureus strains, including clinical isolates. Mutation of fosB or bshA caused a 16-to 60-fold reduction in fosfomycin resistance in these S. aureus strains. High-pressure liquid chromatography analysis, which quantified thiol extracts, revealed some variability in the amounts of BSH present across S. aureus strains. Deletion of fosB led to a decrease in BSH levels. The fosB and bshA mutants of strain COL and a USA300 isolate, upon further characterization, were found to be sensitive to H 2 O 2 and exhibited decreased NADPH levels compared with those in the isogenic parents. Microarray analyses of COL and the isogenic bshA mutant revealed increased expression of genes involved in staphyloxanthin synthesis in the bshA mutant relative to that in COL under thiol stress conditions. However, the bshA mutant of COL demonstrated decreased survival compared to that of the parent in human wholeblood survival assays; likewise, the naturally BSH-deficient strain SH1000 survived less well than its BSH-producing isogenic counterpart. Thus, the survival of S. aureus under oxidative stress is facilitated by BSH, possibly via a FosB-mediated mechanism, independently of its capability to produce staphyloxanthin.

The impacts of pathogen emergence in naïve hosts can be catastrophic, and pathogen spread now ranks as a major threat to biodiversity. However, pathogen impacts can persist for decades after epidemics and produce variable host outcomes. Chytridiomycosis in amphibians (caused by the fungal pathogen Batrachochytrium dendrobatidis, Bd) is an exemplar, with impacts ranging from rapid population crashes and extinctions, to population declines and subsequent recoveries. Here, we investigate long-term impacts associated with chytridiomycosis in Australia. We conducted a continent-wide assessment of the disease, reviewing data collected since the arrival of Bd in about 1978, to assess and characterize mechanisms driving past, present and future impacts. We found chytridiomycosis to be implicated in the extinction or decline of 43 of Australia's 238 amphibian species. Population trajectories of declined species are highly variable; six species are experiencing ongoing declines, eight species are apparently stable and 11 species are recovering. Our results highlight that while some species are expanding, Bd continues to threaten species long after its emergence. Australian case-studies and synthesis of the global chytridiomycosis literature suggests that amphibian reservoir hosts are associated with continued declines in endemically infected populations, while population stability is promoted by environmental conditions that restrict Bd impact, and maintenance of high recruitment capacity that can offset mortality. Host genetic adaptation or decreased pathogen virulence may facilitate species recovery, but neither has been empirically demonstrated. Understanding processes that influence Bd-host dynamics and population persistence is crucial for assessing species extinction risk and identifying strategies to conserve disease-threatened species.