Rain triggers seasonal stratification in a temperate shelf sea.

The North Atlantic Storm Track acts as a conveyor belt for extratropical cyclones that frequently deliver high winds and rainfall to northwest European shelf seas. Storms are primarily considered detrimental to shelf sea stratification due to wind-driven mixing countering thermal buoyancy, but their impact on shelf scale stratification cycles remains poorly understood. Here, we show that storms trigger stratification through enhanced surface buoyancy from rainfall. A multidecadal model confirms that rainfall contributed to triggering seasonal stratification 88% of the time from 1982 to 2015. Stratification could be further modulated by large-scale climate oscillations, such as the Atlantic Multidecadal Variability (AMV), with stratification onset dates being twice as variable during a positive AMV phase than a negative one. Further insights into how changing storm activity will impact shelf seas are discussed beyond the current view of increasing wind-driven mixing, with significant implications for marine productivity and ecosystem function.

Arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae.

• Differential resistance to arsenate (AsO4 3- ) is demonstrated here among populations of the ericoid mycorrhizal fungus Hymenoscyphus ericae isolated from Calluna vulgaris in natural heathland soils and soils contaminated with AsO4 3- . • Isolates (c. 25) of the fungus from each of two As and Cu mine sites, and a natural heathland site, were screened for AsO4 3- and Cu2+ resistance by growing isolates in media containing a range of AsO4 3- and Cu2+ concentrations. • H. ericae populations from the mine sites demonstrated resistance to AsO4 3- compared with the heathland population; the mine-site populations producing significant growth at the highest AsO4 3- concentration (4.67 mol m-3 ), whereas growth of the heathland population was almost completely inhibited. EC50 values for mine-site isolates were estimated to be 5-41-times higher than the heathland population. All isolates produced identical responses to increasing Cu2+ concentrations, with no differences observed between mine-site and heathland isolates. • Populations of H. ericae on the contaminated mine sites have developed adaptive resistance to AsO4 3- . By contrast, Cu2+ resistance appears to be constitutive.

Mechanism of arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae.

Arsenate resistance is exhibited by the ericoid mycorrhizal fungus Hymenoscyphus ericae collected from As-contaminated mine soils. To investigate the mechanism of arsenate resistance, uptake kinetics for arsenate (H(2)AsO(4)(-)), arsenite (H(3)AsO(3)), and phosphate (H(2)PO(4)(-)) were determined in both arsenate-resistant and -non-resistant H. ericae. The uptake kinetics of H(2)AsO(4)(-), H(3)AsO(3), and H(2)PO(4)(-) in both resistant and non-resistant isolates were similar. The presence of 5.0 microM H(2)PO(4)(-) repressed uptake of H(2)AsO(4)(-) and exposure to 0.75 mM H(2)AsO(4)(-) repressed H(2)PO(4)(-) uptake in both H. ericae. Mine site H. ericae demonstrated an enhanced As efflux mechanism in comparison with non-resistant H. ericae and lost approximately 90% of preloaded cellular As (1-h uptake of 0.22 micromol g(-1) dry weight h(-1) H(2)AsO(4)(-)) over a 5-h period in comparison with non-resistant H. ericae, which lost 40% of their total absorbed H(2)AsO(4)(-). As lost from the fungal tissue was in the form of H(3)AsO(3). The results of the present study demonstrate an enhanced H(3)AsO(3) efflux system operating in mine site H. ericae as a mechanism for H(2)AsO(4)(-) resistance. The ecological significance of this mechanism of arsenate resistance is discussed.

Genetic diversity of root-associated fungal endophytes from Calluna vulgaris at contrasting field sites.

A total of 107 putative ericoid mycorrhizal endophytes were isolated from hair roots of Calluna vulgaris from two abandoned arsenic/copper mine sites and a natural heathland site in southwest England. The endophytes were initially grouped as 14 RFLP types, based on the results of ITS-RFLP analysis using the restriction endonucleases Hinf I, Rsa I and Hae III. ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with sequences for known ericoid mycorrhizal endophytes and selected ascomycetes. The majority of endophyte isolates (62-92%) from each site were identified as Hymenoscyphus ericae, but a number of other less common mycorrhizal RFLP types were also identified, all of which appear to have strong affinities with the order Leotiales. None of the less common RFLP types was isolated from C. vulgaris at more than one field site. Neighbour-joining analysis indicated similarities between the endophytes from C. vulgaris and mycorrhizal endophytes isolated from other Ericaceae and Epacridaceae hosts in North America and Australia.

Structure of the O-specific polysaccharide for Acinetobacter baumannii serogroup O1.

A polymeric fraction containing D-galactose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine was isolated from the lipopolysaccharide produced by the reference strain for Acinetobacter baumannii serogroup O1. By means of NMR spectroscopy, methylation analysis, and chemical degradation, the repeating unit of the polymer was identified as a branched trisaccharide of the following structure. [formula: see text].

Assimilation of inorganic nitrogen by a mycobiont isolated from Pisonia grandis R. Br. (Nyctaginaceae) mycorrhiza.

Single isolates of a mycobiont isolated from Pisonia grandis R. Br., Pisolithus tinctorius (Pers.) Coker & Couch and Tylospora fibrillosa (Burt.) Donk were compared with regard to their relative abilities to produce key enzymes of inorganic nitrogen assimilation. Nitrate reductase (NR) activities in the P. grandis mycobiont and T. fibrillosa were significantly lower than in P. tinctorius. While specific activities for glutamate dehydrogenase (GDH) were higher in P. tinctorius than the other two fungi following NH4 (+) pre-treatment, glutamine synthetase (GS) activity did not differ significantly between the three fungi. In all three fungi, specific activities for GS were significantly higher than for GDH. NR activity was expressed in all three fungi regardless of the nitrogen source in the medium, but in P. tinctorius diminished following continued exposure to either NO3 (-), NH4 (+), glutamine or NO3 (-) + glutamine. The data are discussed in relation to nitrogen utilisation by the P. grandis mycobiont.

Lithium clearance in man: effects of dietary salt intake, acute changes in extracellular fluid volume, amiloride and frusemide.

1. The effects of amiloride and frusemide on lithium clearance were studied during changes in dietary sodium chloride intake and during infusion of 0.9% NaCl in normal human volunteers. 2. Lithium and fractional lithium clearances were less on the low than on the high salt diet. Values for the medium salt diet were intermediate. Acute extracellular fluid volume expansion with 0.9% NaCl infusion and extracellular fluid volume contraction 3-4 h after intravenous frusemide caused lithium and fractional lithium clearances to increase and decrease respectively. 3. Amiloride caused small changes in lithium and fractional lithium clearances on a low salt diet, but was without effect when salt intake was medium or high. 4. Increases in lithium clearance occurred immediately after frusemide irrespective of dietary salt intake and in subjects infused with 0.9% NaCl. Only in salt-depleted subjects did frusemide cause a substantial increase in fractional lithium clearance. Changes induced under other circumstances were small. 5. It is concluded that the lithium clearance method for assessment of proximal tubule salt and water reabsorption can be used with some degree of confidence in certain circumstances (medium and high salt intake as well as in acute volume expansion) but may not be reliable when dietary salt intake is low.