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In intertidal sediments, circadian oscillations (i.e., tidal and diel rhythms) and/or depth may affect prokaryotic activity. However, it is difficult to distinguish the effect of each single force on active community changes in these natural and complex intertidal ecosystems. Therefore, we developed a tidal mesocosm to control the tidal rhythm and test whether diel fluctuation or sediment depth influence active prokaryotes in the top 10 cm of sediment. Day- and nighttime emersions were compared as they are expected to display contrasting conditions through microphytobenthic activity in five different sediment layers. A multiple factor analysis revealed that bacterial and archaeal 16S ribosomal RNA (rRNA) transcript diversity assessed by pyrosequencing was similar between day and night emersions. Potentially active benthic Bacteria were highly diverse and influenced by chlorophyll a and phosphate concentrations. While in oxic and suboxic sediments, Thaumarchaeota Marine Group I (MGI) was the most active archaeal phylum, suggesting the importance of the nitrogen cycle in muddy sediments, in anoxic sediments, the mysterious archaeal C3 group dominated the community. This work highlighted that active prokaryotes organize themselves vertically within sediments independently of diel fluctuations suggesting adaptation to physicochemical-specific conditions associated with sediment depth.

Purpose: The objective of his study was to compare the visual and anatomical outcomes in treatment-naïve patients with macular edema secondary to retinal vein occlusion after intravitreal injections of dexamethasone implants (DEX) and anti-VEGF., Methods: One hundred two patients (64 in the anti-VEGF group, 38 in the DEX group) without previous treatment were included in this multi-center retrospective study and evaluated at baseline and 1, 3, 6, and 12 months after the onset of treatment. Patients were defined as "good responders" if central macular thickness (CMT) was less than or equal to 250 μm in TD-OCT or 300 μm in SD-OCT after the injections., Results: At month 3 (n = 102), BCVA had increased significantly, by 0.1 ± 0.3 logMAR in the anti-VEGF group (p = 0.04) and 0.4 ± 0.4 logMAR in the DEX group (p < 0.001); the difference between the two groups was statistically significant (p = 0.007). CMT decreased significantly, by 138 ± 201 μm (-19 %, p < 0.001) in the anti-VEGF group and 163 ± 243 μm (-21 %, p < 0.001) in the DEX group. After 3 months, five patients (13 %) in the DEX group and 20 (31 %) in the anti-VEGF group (p < 0.001) changed treatment. Among the 77 patients who did not switch from their initial treatment, no significant functional or anatomical difference between the two groups was observed at months 6 and 12. Elevation of intraocular pressure > 21 mmHg was more frequent in the DEX group (21 %) than in the anti-VEGF group (3 %, p = 0.008)., Conclusions: Visual acuity recovery was better in the DEX group than in the anti-VEGF group at month 3, but with no difference in CMT. In patients who did not change treatment, the long-term anatomical and visual outcome was similar between the DEX and anti-VEGF groups.

Although microorganisms are the primary drivers of biogeochemical cycles, the structure and functioning of microbial food webs are poorly studied. This is the case in Sphagnum peatlands, where microbial communities play a key role in the global carbon cycle. Here, we explored the structure of the microbial food web from a Sphagnum peatland by analyzing (1) the density and biomass of different microbial functional groups, (2) the natural stable isotope (δ(13)C and δ(15)N) signatures of key microbial consumers (testate amoebae), and (3) the digestive vacuole contents of Hyalosphenia papilio, the dominant testate amoeba species in our system. Our results showed that the feeding type of testate amoeba species (bacterivory, algivory, or both) translates into their trophic position as assessed by isotopic signatures. Our study further demonstrates, for H. papilio, the energetic benefits of mixotrophy when the density of its preferential prey is low. Overall, our results show that testate amoebae occupy different trophic levels within the microbial food web, depending on their feeding behavior, the density of their food resources, and their metabolism (i.e., mixotrophy vs. heterotrophy). Combined analyses of predation, community structure, and stable isotopes now allow the structure of microbial food webs to be more completely described, which should lead to improved models of microbial community function.

The main goal of this work was to study the dynamics and biochemical composition of extracellular polysaccharides (ECPS), a fraction of the extracellular polymeric substances (EPS) produced during the development of a microphytobenthic biofilm in a European intertidal mudflat (Marennes-Oléron Bay, France) during winter. Microphytobenthic biomass was surveyed during four consecutive emersion periods to confirm the biofilm growth. Bacteria abundance was also checked considering the importance of heterotrophic bacteria observed by various authors in the dynamics of EPS. Various colorimetric assays, coupled to biochemical chromatographic analysis, were used to characterize the three main fractions of extracted EPS: colloidal, bound, and residual. The monosaccharide distribution of colloidal ECPS highlighted their role of carbon source for bacteria (>50% of glucose) even if no increase of colloidal carbohydrate amounts was observed during the tidal exposure. Bound ECPS were composed of deoxy or specific sugars (30% rhamnose) and uronic acids (18% galacturonic acid). Their levels and dynamics could be correlated to the development of the microphytobenthic biofilm, enhancing the stabilization of the sediment or increasing binding forces accordingly. Residual fractions, containing refractory bound ECPS and other internal polymeric substances, were composed of various carbohydrates. The high ratio of glucose in these fractions (18% to 43%) was interesting, as it was once attributed to colloidal sugars due to poor extraction procedures. Finally, the presence of inositol (15%) was significant since no author has highlighted it before, knowing that inositol is a major growth factor for heterotrophic bacteria.