Timing the evolution of phosphorus-cycling enzymes through geological time using phylogenomics.

Phosphorus plays a crucial role in controlling biological productivity, but geological estimates of phosphate concentrations in the Precambrian ocean, during life's origin and early evolution, vary over several orders of magnitude. While reduced phosphorus species may have served as alternative substrates to phosphate, their bioavailability on the early Earth remains unknown. Here, we reconstruct the phylogenomic record of life on Earth and find that phosphate transporting genes (pnas) evolved in the Paleoarchean (ca. 3.6-3.2 Ga) and are consistent with phosphate concentrations above modern levels ( > 3 µM). The first gene optimized for low phosphate levels (pstS; <1 µM) appeared around the same time or in the Mesoarchean depending on the reconstruction method. Most enzymatic pathways for metabolising reduced phosphorus emerged and expanded across the tree of life later. This includes phosphonate-catabolising CP-lyases, phosphite-oxidising pathways and hypophosphite-oxidising pathways. CP-lyases are particularly abundant in dissolved phosphate concentrations below 0.1 µM. Our results thus indicate at least local regions of declining phosphate levels through the Archean, possibly linked to phosphate-scavenging Fe(III), which may have limited productivity. However, reduced phosphorus species did not become widely used until after the Paleoproterozoic Great Oxidation Event (2.3 Ga), possibly linked to expansion of the biosphere at that time.

Increasing transposase abundance with ocean depth correlates with a particle-associated lifestyle.

Transposases are mobile genetic elements that move within and between genomes, promoting genomic plasticity in microorganisms. In marine microbial communities, the abundance of transposases increases with depth, but the reasons behind this trend remain unclear. Our analysis of metagenomes from the Tara Oceans and Malaspina Expeditions suggests that a particle-associated lifestyle is the main covariate for the high occurrence of transposases in the deep ocean, and this trend holds true for individual genomes as well as in a community-wide sense. We observed a strong and depth-independent correlation between transposase abundance and the presence of biofilm-associated genes, as well as the prevalence of secretory enzymes. This suggests that mobile genetic elements readily propagate among microbial communities within crowded biofilms. Furthermore, we show that particle association positively correlates with larger genome size, which is in turn associated with higher transposase abundance. Cassette sequences associated with transposons are enriched with genes related to defense mechanisms, which are more highly expressed in the deep sea. Thus, while transposons spread at the expense of their microbial hosts, they also introduce novel genes and potentially benefit the hosts in helping to compete for limited resources. Overall, our results suggest a new understanding of deep ocean particles as highways for gene sharing among defensively oriented microbial genomes.IMPORTANCEGenes can move within and between microbial genomes via mobile genetic elements, which include transposases and transposons. In the oceans, there is a puzzling increase in transposase abundance in microbial genomes as depth increases. To gain insight into this trend, we conducted an extensive analysis of marine microbial metagenomes and metatranscriptomes. We found a significant correlation between transposase abundance and a particle-associated lifestyle among marine microbes at both the metagenome and genome-resolved levels. We also observed a link between transposase abundance and genes related to defense mechanisms. These results suggest that as microbes become densely packed into crowded particles, mobile genes are more likely to spread and carry genetic material that provides a competitive advantage in crowded habitats. This may enable deep sea microbes to effectively compete in such environments.

Uncertainty analysis of ecosystem services and implications for environmental management - An experiment in the Heihe River Basin, China.

Integrating the economic values of ecosystem services provided by different land uses into decision analysis is critical to achieving effective environmental management in endorheic basins. However, policymaking often ignores the uncertainty related to the variability of parameters in ecosystem service values. To this end, we identified sensitive parameters in the ecosystem service values under four land uses using the global sensitivity analysis method and quantified the potential monetary outcomes based on the Monte Carlo method. The results indicated that only a few sensitive parameters, such as water yield (Qi) and treatment costs per unit of nitrogen (Cost_N), were the primary sources of uncertainty. Therefore, we suggest that improving the precision of sensitive parameters is essential for reducing uncertainty in the total ecosystem service value. Additionally, the overall monetary outcomes for cropland exhibited negative values and had higher risk and lower benefits than those for forest from the standpoint of ecosystem services. In addition, the nonmarketed service of landscape aesthetic made the monetary outcomes of water bodies higher than those of cropland, yet the value of landscape aesthetic was highly uncertain. Therefore, efforts should be made to improve total monetary outcomes by decreasing the negative values in food provisioning of cropland and the uncertainty in landscape aesthetic for water bodies. The sensitivity analysis and uncertainty analysis provide important guidelines for quantifying and reducing the related uncertainty and provide policy information for environmental management based on a comprehensive consideration of the potential ecosystem service values for various land uses.

[Development mechanism of concentrated poverty areas under the sustainable livelihood: The example of the development-restricted ecological district of Ningxia, Northwest China].

Livelihood capital has a close relationship with the income and expenditure of farmers' households. For example, the survival strategies of farmers' households are determined by it and it also influences regional development mechanisms and models. Under the analysis framework of sustainable livelihoods, this study evaluated farmers' livelihood capital, income, and expenditure, based on a participatory rural appraisal and a statistical method, in the development-restricted ecological district of Ningxia, decomposed into the nationality, terrain, and type of farmers' household. Further, by using an index of non-farm business households, the correlations between the livelihood capital and income with the expenditure of farmers' households and the index of non-farm business households were quantified to understand the mechanism of regional development. The results showed that livelihood capital was generally low in the study area. In particular, the livelihood capital of Hui nationality households was slightly higher than that of Han nationality households, that of river valley households was higher than that of mountain households, and that of combined occupation households and non-farm business households was significantly higher than that of agricultural households. Moreover, there was a significant positive correlation between the net annual income of farmers' households and the non-agricultural index, human capital, physical capital, and financial capital, while a significant negative correlation existed between net annual income and natural capital. These findings suggested that efforts were required to enhance the capacity of the non-agricultural index and the human, material, and other capital in the study area. They also served as a guideline for the circulation of peasants' means of production in order to accelerate the polarization of natural capital.