Guide-free Cas9 from pathogenic Campylobacter jejuni bacteria causes severe damage to DNA

CRISPR-Cas9 systems are enriched in human pathogenic bacteria and have been linked to cytotoxicity by an unknown mechanism. Here, we show that upon infection of human cells, Campylobacter jejuni secretes its Cas9 (CjeCas9) nuclease into their cytoplasm. Next, a native nuclear localization signal enables CjeCas9 nuclear entry, where it catalyzes metal-dependent nonspecific DNA cleavage leading to cell death. Compared to CjeCas9, native Cas9 of Streptococcus pyogenes (SpyCas9) is more suitable for guide-dependent editing. However, in human cells, native SpyCas9 may still cause some DNA damage, most likely because of its ssDNA cleavage activity. This side effect can be completely prevented by saturation of SpyCas9 with an appropriate guide RNA, which is only partially effective for CjeCas9. We conclude that CjeCas9 plays an active role in attacking human cells rather than in viral defense. Moreover, these unique catalytic features may therefore make CjeCas9 less suitable for genome editing applications

The GEOTRACES Intermediate Data Product 2014

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-? data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes

Distributions and Sources of Dissolved Iron in the Polar Oceans

De beschikbaarheid van ijzer is van wezenlijk belang voor de groei van algen in de oceanen, en daarmee de gehele voedselketen in de oceaan. In dit onderzoek is gekeken naar de verspreiding en bronnen van ijzer in de Poolzeeen. Opgelost ijzer is gemeten in hoge resolutie in watermonsters verdeeld over de gehele diepte van de Oceaan. In de Arctische Oceaan is gebleken dat water met hoge ijzerconcentraties van de Siberische rivieren wordt vervoerd met de Transpolar Drift tot het midden van de Arctische Oceaan. Verder richting de Canadese kant van de Arctische Oceaan neemt het ijzer weer af, en wordt de concentratie vooral bepaald door smeltend ijs en biologische factoren. In de diepe Arctische Ocean blijken onderzeese vulkanen een belangrijke bron van ijzer. In het Makarov Bassin is een lage concentratie gemeten, dankzij het ontbreken van bronnen en de invloed van organische liganden. In de Zuidelijke Oceaan is een inverse relatie gevonden tussen fluorescentie, indicatief voor algengroei, en opgelost ijzer. De gebruikelijke toename van ijzer richting het continentale plat is afwezig in de Weddell Zee, waarschijnlijk door de ijskap die tot ver in de Oceaan reikt. Lokale ijzebronnen zijn atmosferische depositie aan het oppervlak en onderzeese vulkanen op diepte. Op de nulmeridiaan is de nitraat:fosfaat en nitraat:silicaat opname toe met opgelost ijzer, terwijl er in de Westelijke Wedell Zee geen relatie was. Dit wordt verklaard door de significant grotere algen rond de nulmeridiaan, voor welke er een groter effect van ijzerconcentratie op de nutrienthuishouding en daarmee op de groei is. The availability of iron is very important for algal growth in the ocean, thus for the entire ocean food web. In this research we investigated the distribution and sources of dissolved iron in the Polar Oceans. Iron is measured in high resolution in water samples divided over the entire depth of the ocean. In the Arctic Ocean it appeared that iron from the Siberian rivers is transported with the Transpolar Drift and reaches the middle of the Arctic Ocean. Further towards the Canadian side, iron concentrations decrease the concentration is determined by melting ice and biological factors. In the deep Arctic Ocean, hydrothermal vents are an important source of iron. In the Makarov Basin, a low iron concentration is attributed to the lack of input sources and the influence of organic ligands. In the Southern Ocean an inverse relation between fluorescence, indicative for algal growth, and dissolved iron is found. The common pattern of increasing iron concentrations towards continental shelves is not present in the Weddell Sea, likely as a result of the ice sheet extending far beyond the continent. Local sources of iron are dust deposition at the surface and hydrothermal vents at depth. At the zero meridian the nitrate:phosphate and nitrate:silicate uptake increases with dissolved iron whereas in the Western Weddell Sea there was no relation. This can be explained by the significantly larger algae at the zero meridian, for which there is a much larger effect of iron on the nutrient uptake and thus on the growth.

Fluxes of dissolved aluminum and manganese to the Weddell Sea and indications for manganese co-limitation

<p>The trace metals aluminum (Al) and manganese (Mn) were studied in the Weddell Sea in March 2008. Concentrations of dissolved Al ([Al]) were slightly elevated (0.23-0.35 nmol L-1) in the surface layer compared to the subsurface minimum (0.07-0.21 nmol L-1) observed in the winter water. Atmospheric deposition is the main source of Al to the central Weddell Sea (22 mu mol m(-2) yr(-1)), and the residence time of dissolved Al in the upper mixed layer is similar to 0.8 yr. The flux from the shelf and slope regions equals about 50% of the atmospheric input of Al to the western Weddell Sea. The highest [Al] in the Weddell Sea bottom water (WSBW) is related to the formation of deep water, and the associated downward flux is in the range of 3-10 mu mol Al m(-2) yr(-1). The concentrations of dissolved Mn ([Mn]) were depleted in the surface layer, likely as a result of biological uptake, as indicated by the correlation among Mn, major nutrients, and fluorescence. The significant negative relation between the Delta Mn:Delta P ratio and the ambient concentration of dissolved iron indicates iron-Mn co-limitation. The flux of Mn from the continental margin is about 2.2 times greater than atmospheric input (1.1 mu mol m(-2) yr(-1)). The flux of both Al and Mn from the continental margin indicates melting of continental ice (icebergs) or direct continental runoff. The slightly elevated [Mn] in the WSBW is due to a relatively small flux of 1 mu mol Mn m(-2) yr(-1) associated with WSBW formation.</p>

Dissolved iron measured on water bottle samples during POLARSTERN cruise ANT-XXIV/3

We report a comprehensive dataset of dissolved iron (Fe) comprising 482 values at 22 complete vertical profiles along a 1° latitudinal section at the Zero meridian. In addition a shorter high resolution (~00°09') surface section of the southernmost part of the transect (66°00' - 69°35' S) is presented. Within the upper surface mixed layer the concentrations of dissolved Fe vary between 0.1 and 0.3 nM. An inverse trend versus fluorescence suggests significant Fe removal by plankton blooms. Vertical mixing and upwelling are the most important supply mechanisms of iron from deep waters to the upper surface mixed layer. At lower latitude (42°S) there is a distinct maximum of 0.6-0.7 nM in the 2000-3000 m depth range due to inflow of North Atlantic Deep Water. In one region (55°S) elevated dissolved Fe found in the surface mixed layer is ascribed to the recent deposition of aeolian dust originating from South America. Close to the Antarctic continent there is an indication of Fe supply in surface waters from icebergs. In the deep waters there is a strong indication of a hydrothermal plume of dissolved Fe and Mn over the ridge in the Bouvet region (52-56°S). In the Weddell Gyre basin the dissolved Fe in the deep water is 0.47±0.16 nM in the eastward flow at ~56-62°S and is lower with a value of 0.34±0.14 nM in the westward flow at high ~62-69°S latitude. At the edge of the continental ice-sheet on the prime meridian, the continental margin of the Antarctic continent appears to be lesser source of dissolved Fe than in any other place in the world; this is likely because it is unique in being overlain by the extending continental ice-sheet that largely prevents biogeochemical cycling

Average fluorescence and dissolved iron and Fe-binding ligand characteristics during POLARSTERN expedition ANT-XXIV/3 in 2008

Organic complexation of dissolved iron (dFe) was investigated in the Atlantic sector of the Southern Ocean in order to understand the distribution of Fe over the whole water column. The total concentration of dissolved organic ligands ([Lt]) measured by voltammetry ranged between 0.54 and 1.84 nEq of M Fe whereas the conditional binding strength (K') ranged between 10**21.4 and 10**22.8. For the first time, trends in Fe-organic complexation were observed in an ocean basin by examining the ratio ([Lt]/[dFe]), defined as the organic ligand concentration divided by the dissolved Fe concentration. The [Lt]/[dFe] ratio indicates the saturation state of the natural ligands with Fe; a ratio near 1 means saturation of the ligands leading to precipitation of Fe. Reversely, high ratios mean Fe depletion and show a high potential for Fe solubilisation. In surface waters where phytoplankton is present low dissolved Fe and high variable ligand concentrations were found. Here the [Lt]/[dFe] ratio was on average 4.4. It was especially high (5.6-26.7) in the HNLC (High Nutrient, Low Chlorophyll) regions, where Fe was depleted. The [Lt]/[dFe] ratio decreased with depth due to increasing dissolved Fe concentrations and became constant below 450 m, indicating a steady state between ligand and Fe. Relatively low [Lt]/[dFe] ratios (between 1.1 and 2.7) existed in deep water north of the Southern Boundary, facilitating Fe precipitation. The [Lt]/[dFe] ratio increased southwards from the Southern Boundary on the Zero Meridian and from east to west in the Weddell Gyre due to changes both in ligand characteristics and in dissolved iron concentration. High [Lt]/[dFe] ratio expresses Fe depletion versus ligand production in the surface. The decrease with depth reflects the increase of [dFe] which favours scavenging and (co-) precipitation, whereas a horizontal increase in the deep waters results from an increasing distance from Fe sources. This increase in the [Lt]/[dFe] ratio at depth shows the very resistant nature of the dissolved organic ligands

Dissolved iron measurements from 44 stations in the shallow Arctic Ocean waters and Shelf Sea's during POLARSTERN cruise ARK-XXII/2

Concentrations of dissolved (10 nM) in the bottom waters of the Laptev Sea shelf may be attributed to either sediment resuspension, sinking of brine or regeneration of DFe in the lower layers. A significant correlation (R**2 = 0.60) between salinity and DFe is observed. Using d18O, salinity, nutrients and total alkalinity data, the main source for the high (>2 nM) DFe concentrations in the Amundsen and Makarov Basins is identified as (Eurasian) river water, transported with the Transpolar Drift (TPD). On the North American side of the TPD, the DFe concentrations are low (4) above the shelf and low (<4) off the shelf)