The abundance & diversity of arbuscular mycorrhizal fungi are linked to the soil chemistry of screes & to slope in the Alpic paleo-endemic Berardia subacaulis

Berardia subacaulis Vill. is a monospecific genus that is endemic to the South-western Alps, where it grows on alpine screes, which are extreme habitats characterized by soil disturbance and limiting growth conditions. Root colonization by arbuscular mycorrhizal fungi (AMF) is presumably of great importance in these environments, because of its positive effect on plant nutrition and stress tolerance, as well as on structuring the soil. However, there is currently a lack of information on this topic. In this paper, we tested which soil characteristics and biotic factors could contribute to determining the abundance and community composition of AMF in the roots of B. subacaulis, which had previously been found to be mycorrhizal. For such a reason, the influence of soil properties and environmental factors on AMF abundance and community composition in the roots of B. subacaulis, sampled on three different scree slopes, were analysed through microscopic and molecular analysis. The results have shown that the AMF community of Berardia roots was dominated by Glomeraceae, and included a core of AMF taxa, common to all three scree slopes. The vegetation coverage and dark septate endophytes were not related to the AMF colonization percentage and plant community did not influence the root AMF composition. The abundance of AMF in the roots was related to some chemical (available extractable calcium and potassium) and physical (cation exchange capacity, electrical conductivity and field capacity) properties of the soil, thus suggesting an effect of AMF on improving the soil quality. The non-metric multidimensional scaling (NMDS) ordination of the AMF community composition showed that the diversity of AMF in the various sites was influenced not only by the soil quality, but also by the slope. Therefore, the slopeinduced physical disturbance of alpine screes may contribute to the selection of disturbancetolerant AMF taxa, which in turn may lead to different plant-fungus assemblages

Correlation between the Percentage of AMF Root Colonization, Soil Properties, Soil Morphology, Vegetation Coverage and DSE Colonization Calculated Using the Kendal Tau.

<p>Correlation between the Percentage of AMF Root Colonization, Soil Properties, Soil Morphology, Vegetation Coverage and DSE Colonization Calculated Using the Kendal Tau.</p

Joint plot of the NMDS ordination of the AMF communities colonizing the <i>B</i>. <i>subacaulis</i> roots in the different plots and the significance vectors (p < 0.1) of the environmental variables across the sites.

<p>The vectors graphically represent the correlations of the NMDS axes to each of the measured variables of the soil. The length of the arrow is proportional to the strength of the correlation between the environmental variables and community dissimilarities. Mg, available magnesium; Na, available sodium; EC, electrical conductivity; SL, slope. Polygons have been used to group the plots in the same site. Symbols: red, filled squares = MIL, Millefonts; blue,filled circles = CLM, Bassa di Colombart, and yellow, filled diamonds = VAL,Valcavera.</p

The abundance and diversity of arbuscular mycorrhizal fungi are linked to the soil chemistry of screes and to slope in the Alpic paleo-endemic <i>Berardia subacaulis</i> - Fig 1

<p><b>Representative images of <i>B</i>. <i>subacaulis</i> roots colonized by arbuscular mycorrhizal fungi (AMF, a-c) and dark septate endophytes (DSE, d-e)</b>. (a) Extensive AMF colonization; (b) arbuscules (A) and intracellular hyphal coils (C); (c) intercellular vesicle (V); (d) DSE hyphae growing on the root epidermis and inside the cortex; (e) microsclerotium (MS); a, bar = 500 μm; b-d, bar = 100 μm; e, bar = 20 μm.</p

The abundance and diversity of arbuscular mycorrhizal fungi are linked to the soil chemistry of screes and to slope in the Alpic paleo-endemic <i>Berardia subacaulis</i> - Fig 3

<p>(a) <b>The ordinated heat-map based on occurrence classes (<1% absent, white, >30% dominant, black; light to dark grey, intermediate percentages) of the fungal operational taxonomic units (OTU’s, rows).</b> The genera, or clade, and the virtual taxa assignments are also indicated for the 31 OTUs. (b) <b>Venn diagram showing the number of shared and site-specific AMF OTUs. (Bassa di Colombart, CLM; Millefonts, MIL; Valcavera, VAL).</b></p

Phylogenetic tree showing the placement of the AM fungal OTUs associated with <i>B</i>. <i>subacaulis</i>.

<p>Reference sequences were retrieved from the MaarjAM AMF Virtual Taxa database [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0171866#pone.0171866.ref041" target="_blank">41</a>]. <i>Corallochytrium limacisporum</i> (L42528) was used as the outgroup taxon.</p

Details of the sampling sites.

<p>Details of the sampling sites.</p

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population