Marine microbes are an important control on the biogeochemical cycling of trace metals, but simultaneously, these metals can control the growth of microorganisms and the cycling of major nutrients like C and N. However, studies on the response/limitation of microorganisms to trace metals have traditionally focused on the response of autotrophic phytoplankton to Fe fertilization. Few reports are available on the response of heterotrophic prokaryotes to Fe, and even less to other biogeochemically relevant metals. We performed the first study coupling dark incubations with next generation sequencing to specifically target the functional and phylogenetic response of heterotrophic prokaryotes to Fe enrichment. Furthermore, we also studied their response to Co, Mn, Ni, Zn, Cu (individually and mixed), using surface and deep samples from either coastal or open-ocean waters. Heterotrophic prokaryotic activity was stimulated by Fe in surface open–ocean, as well as in coastal, and deep open-ocean waters (where Zn also stimulated). The most susceptible populations to trace metals additions were uncultured bacteria (e.g., SAR324, SAR406, NS9, and DEV007). Interestingly, hydrocarbon-degrading bacteria (e.g., Thalassolituus, Marinobacter, and Oleibacter) benefited the most from metal addition across all waters (regions/depths) revealing a predominant role in the cycling of metals and organic matter in the ocean.

Morales et al. Fronts are ecotones but not diversity hotspotsEcotones are regarded as diversity hotspots in terrestrial systems, but it is 1 unknown if this "ecotone effect" occurs in the marine environment. Oceanic

Ecotones are regarded as diversity hotspots in terrestrial systems, but it is unknown if this 'ecotone effect' occurs in the marine environment. Oceanic fronts are widespread mesoscale features, present in the boundary between different water masses, and are arguably the best potential examples of ecotones in the ocean. Here we performed the first seasonal study along an oceanic front, combining 16S rRNA gene sequencing coupled with a high spatial resolution analysis of the physical properties of the water masses. Using the Subtropical Frontal Zone off New Zealand we demonstrate that fronts delimit shifts in bacterioplankton community composition between water masses, but that the strength of this effect is seasonally dependent. While creating a transition zone where physicochemical parameters and bacterioplankton communities get mixed, this ecotone does not result in increased diversity. Thus unlike terrestrial ecotones, oceanic fronts are boundaries but not hotspots of bacterioplankton diversity in the ocean.

An extra oral approach was made to 26 pairs of Wistar rat incisors and a small bur used to expose the pulps which were then dressed with either calcium hydroxide paste (Pulpdent) zinc oxide-eugenol cement (Kalzinol) or a triamocinolone acetonide/tetracycline containing cement (Ledermix). Animals were sacrificed at 7 days, incisors removed, a window cut to the pulp opposite the site of exposure, soft tissues removed with 7% NaOCl for 30 minutes before teeth were dehydrated in graded concentrations of acetone and gold coated for examination under SEM. Calcium hydroxide produced rapid complete repair with a remarkably regular formation of calcospherites, except for a zone of relative inhibition perforated by nutrient canals at the periphery of each lesion. Both zinc oxide-eugenol and triamcinolone acetonide cements inhibited both bridging of the defect created by the exposure and dentine formation in the surrounding pulpal wall. Data was grouped according to the degree of hard tissue repair. The results were statistically significant (Chi-square p < or = 0.001). This method demonstrated qualitative and quantitative differences in the repair process resulting from chemical variations in the dressings applied.

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