Biogeographic gradients of picoplankton diversity indicate increasing dominance of prokaryotes in warmer Arctic fjords.

Climate change is opening the Arctic Ocean to increasing human impact and ecosystem changes. Arctic fjords, the region's most productive ecosystems, are sustained by a diverse microbial community at the base of the food web. Here we show that Arctic fjords become more prokaryotic in the picoplankton (0.2-3 µm) with increasing water temperatures. Across 21 fjords, we found that Arctic fjords had proportionally more trophically diverse (autotrophic, mixotrophic, and heterotrophic) picoeukaryotes, while subarctic and temperate fjords had relatively more diverse prokaryotic trophic groups. Modeled oceanographic connectivity between fjords suggested that transport alone would create a smooth gradient in beta diversity largely following the North Atlantic Current and East Greenland Current. Deviations from this suggested that picoeukaryotes had some strong regional patterns in beta diversity that reduced the effect of oceanographic connectivity, while prokaryotes were mainly stopped in their dispersal if strong temperature differences between sites were present. Fjords located in high Arctic regions also generally had very low prokaryotic alpha diversity. Ultimately, warming of Arctic fjords could induce a fundamental shift from more trophic diverse eukaryotic- to prokaryotic-dominated communities, with profound implications for Arctic ecosystem dynamics including their productivity patterns.

Microbial communities from arid environments on a global scale. A systematic review.

Arid environments are defined by the lack of water availability, which is directly related to the mean annual precipitation (MAP), and high values of solar irradiation, which impacts the community composition of animals, plants, and the microbial structure of the soil. Recent advances in NGS technologies have expanded our ability to characterize microbiomes, allowing environmental microbiologists to explore the complete microbial structure. Intending to identify and describe the state-of-the-art of bacterial communities in arid soils at a global scale, and to address the effect that some environmental features may have on them, we performed a systematic review based on the PRISMA guideline. Using a combination of keywords, we identified a collection of 66 studies, including 327 sampled sites, reporting the arid soil bacterial community composition by 16S rDNA gene high-throughput sequencing. To identify factors that can modulate bacterial communities, we extracted the geographical, environmental, and physicochemical data. The results indicate that even though each sampled site was catalogued as arid, they show wide variability in altitude, mean annual temperature (MAT), soil pH and electric conductivity, within and between arid environments. We show that arid soils display a higher abundance of Actinobacteria and lower abundance of Proteobacteria, Cyanobacteria, and Planctomycetes, compared with non-arid soil microbiomes, revealing that microbial structure seems to be strongly modulated by MAP and MAT and not by pH in arid soils. We observed that environmental and physicochemical features were scarcely described among studies, hence, we propose a reporting guideline for further analysis, which will allow deepening the knowledge of the relationship between the microbiome and abiotic factors in arid soil. Finally, to understand the academic collaborations landscape, we developed an analysis of the author's network, corroborating a low degree of connectivity and collaborations in this research topic. Considering that it is crucial to understand how microbial processes develop and change in arid soils, our analysis emphasizes the need to increase collaborations between research groups worldwide.

Microbial communities from arid environments on a global scale: a systematic review

Abstract Arid environments are defined by the lack of water availability, which is directly related to the mean annual precipitation (MAP), and high values of solar irradiation, which impacts the community composition of animals, plants, and the microbial structure of the soil. Recent advances in NGS technologies have expanded our ability to characterize micro- biomes, allowing environmental microbiologists to explore the complete microbial structure. Intending to identify and describe the state-of-the-art of bacterial communities in arid soils at a global scale, and to address the effect that some environmental features may have on them, we performed a systematic review based on the PRISMA guideline. Using a combination of keywords, we identified a collection of 66 studies, including 327 sampled sites, reporting the arid soil bacterial community composition by 16S rDNA gene high-throughput sequencing. To identify factors that can modulate bacterial communities, we extracted the geographical, environmental, and physicochemical data. The results indicate that even though each sampled site was catalogued as arid, they show wide variability in altitude, mean annual temperature (MAT), soil pH and electric conductivity, within and between arid environments. We show that arid soils display a higher abundance of Actinobacteria and lower abundance of Proteobacteria, Cyanobacteria, and Planctomycetes, compared with non-arid soil microbiomes, revealing that microbial structure seems to be strongly modulated by MAP and MAT and not by pH in arid soils. We observed that environmental and physicochemical features were scarcely described among studies, hence, we propose a reporting guideline for further analysis, which will allow deepening the knowledge of the relationship between the microbiome and abiotic factors in arid soil. Finally, to understand the academic collaborations landscape, we developed an analysis of the author's network, corroborating a low degree of connectivity and collaborations in this research topic. Considering that it is crucial to understand how microbial processes develop and change in arid soils, our analysis emphasizes the need to increase collaborations between research groups worldwide.

Andrographolide recovers cognitive impairment in a natural model of Alzheimer's disease (Octodon degus).

The social species Octodon degus (degu) is the only wild-type South American rodent that develops Alzheimer's-like pathology with age. Here, we evaluated the ability of a natural product (Andrographolide, ANDRO), a diterpene of the labdane family obtained from the Asian plant Andrographis paniculata, to recover the cognitive decline in this long-lived animal model. We administered ANDRO to aged degus (56-month old) for 3 months. In addition, in 2 control groups (young degus: 12-month old and aged degus: 56-month old), we administrated saline solution as a vehicle. We evaluated cognitive performance through several behavioral tests. We also performed a series of physiological and biochemical analyses (e.g., electrophysiological and immunoblotting assessment) to identify possible mechanisms underlying cognitive performance associated with age. Our results suggest that there is an effect of aging on the loss of cognitive function, and this decrease in cognitive function was also related to a decrease in the synaptic functions and an increase in the main hallmarks of Alzheimer's disease (AD). More importantly, ANDRO treatments showed the following beneficial effects: (1) recovery of spatial memory and learning performance; (2) recovery of synaptic basal transmission; (3) partial or complete protection of certain synaptic proteins; and (4) a specific neuroprotective effect, including the reduction of phosphorylated tau protein and amyloid beta aggregate maturation in aged degus. Taken together, our results suggest that ANDRO could be used as a potential therapy for AD and support the use of O. degus as a natural model in which to study both neural damage associated with aging processes and the behavioral and neuropathological hallmarks of aging-related diseases such as AD.