Leaching patterns on sulfide minerals were investigated by high-resolution scanning electron microscopy (SEM). Our goal was to evaluate the relative contributions of inorganic surface reactions and reactions localized by attached cells to surface morphology evolution. Experiments utilized pyrite (FeS2), marcasite (FeS2) and arsenopyrite (FeAsS), and two iron-oxidizing prokaryotes in order to determine the importance of cell type, crystal structure, and mineral dissolution rate in microbially induced pit formation. Pyrite surfaces were reacted with the iron-oxidizing bacterium Acidithiobacillus ferrooxidans (at 25°C), the iron-oxidizing archaeon 'Ferroplasma acidarmanus' (at 37°C), and abiotically in the presence of Fe3+ ions. In all three experiments, discrete bacillus-sized (1–2 μm) and -shaped (elliptical) pits developed on pyrite surfaces within 1 week of reaction. Results show that attaching cells are not necessary for pit formation on pyrite. Marcasite and arsenopyrite surfaces were reacted with A. ferrooxidans (at 25°C) and 'F. acidarmanus' (at 37°C). Cell-sized and cell-shaped dissolution pits were not observed on marcasite or arsenopyrite at any point during reaction with A. ferrooxidans, or on marcasite surfaces reacted with 'F. acidarmanus'. However, individual 'F. acidarmanus' cells were found within individual shallow (<0.5 μm deep) pits. The size and shape (round rather than elliptical) of the pits conformed closely to the shape of F. acidarmanus (cells) pits on arsenopyrite. We infer these pits to be cell-induced. We attribute the formation of pits readily detectable (by SEM) to the higher reactivity of arsenopyrite compared to pyrite and marcasite under the conditions the experiment was conducted. These pits contributed little to the overall surface topographical evolution, and most likely did not significantly increase surface area during reaction. Our results suggest that overall sulfide mineral dissolution may be dominated by surface reactions with Fe3+ rather than by reactions at the cell–mineral interface.
The availability of food high in fat, salt and sugar through Fast Food (FF) or takeaway outlets, is implicated in the causal pathway for the obesity epidemic. This review aims to summarise this body of research and highlight areas for future work. Thirty three studies were found that had assessed the geography of these outlets. Fourteen studies showed a positive association between availability of FF outlets and increasing deprivation. Another 13 studies also included overweight or obesity data and showed conflicting results between obesity/overweight and FF outlet availability. There is some evidence that FF availability is associated with lower fruit and vegetable intake. There is potential for land use policies to have an influence on the location of new FF outlets. Further research should incorporate good quality data on FF consumption, weight and physical activity.
Reporter lines generated in human pluripotent stem cells can be highly useful for the analysis of specific cell types and lineages in live cultures. We created the first human rod reporter line using CRISPR/Cas9 genome editing to replace one allele of the Neural Retina Leucine zipper (NRL) gene with an eGFP transgene in the WA09 human embryonic stem cell (hESC) line. After confirming successful targeting, three-dimensional optic vesicle structures were produced to examine reporter specificity and to track rod differentiation in culture. The NRL+/eGFP hESC line robustly and exclusively labeled the entirety of rods throughout differentiation, eventually revealing highly mature structural features. This line provides a valuable tool for studying human rod development and disease and testing therapeutic strategies for retinitis pigmentosa.
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