Spatial Patterns of Soil Fungal Communities Are Driven by Dissolved Organic Matter (DOM) Quality in Semi-Arid Regions.

Soil fungi are ecologically important as decomposers, pathogens, and symbionts in nature. Understanding their biogeographic patterns and driving forces is pivotal to predict alterations arising from environmental changes in ecosystem. Dissolved organic matter (DOM) is an essential resource for soil fungi; however, the role of its quality in structuring fungal community patterns remains elusive. Here using Illumina MiSeq sequencing, we characterized total fungi and their functional groups in 45 soil samples collected from a 1500-km sampling transect through semi-arid regions in northern China, which are currently suffering great pressure from climate change. Total fungi and their functional groups were all observed to exhibit significant biogeographic patterns which were primarily driven by environmental variables. DOM quality was the best and consistent predictor of diversity of both total fungi and functional groups. Specifically, plant-derived DOM was associated with greater diversity relative to microbe-dominated origins. In addition, fungal diversity linearly increased with increases in degree of humification in DOM. Similarly, among all measured environmental variables, DOM quality had the strongest effects on the community composition of total fungi and functional groups. Together, our work contributes to the factors underlying fungal biogeographic patterns and adds detail to the importance of DOM quality in structuring fungal communities.

Long-term oil contamination causes similar changes in microbial communities of two distinct soils.

Since total petroleum hydrocarbons (TPH) are toxic and persistent in environments, studying the impact of oil contamination on microbial communities in different soils is vital to oil production engineering, effective soil management and pollution control. This study analyzed the impact of oil contamination on the structure, activity and function in carbon metabolism of microbial communities of Chernozem soil from Daqing oil field and Cinnamon soil from Huabei oil field through both culture-dependent techniques and a culture-independent technique-pyrosequencing. Results revealed that pristine microbial communities in these two soils presented disparate patterns, where Cinnamon soil showed higher abundance of alkane, (polycyclic aromatic hydrocarbons) PAHs and TPH degraders, number of cultivable microbes, bacterial richness, bacterial biodiversity, and stronger microbial activity and function in carbon metabolism than Chernozem soil. It suggested that complicated properties of microbes and soils resulted in the difference in soil microbial patterns. However, the changes of microbial communities caused by oil contamination were similar in respect of two dominant phenomena. Firstly, the microbial community structures were greatly changed, with higher abundance, higher bacterial biodiversity, occurrence of Candidate_division_BRC1 and TAO6, disappearance of BD1-5 and Candidate_division_OD1, dominance of Streptomyces, higher percentage of hydrocarbon-degrading groups, and lower percentage of nitrogen-transforming groups. Secondly, microbial activity and function in carbon metabolism were significantly enhanced. Based on the characteristics of microbial communities in the two soils, appropriate strategy for in situ bioremediation was provided for each oil field. This research underscored the usefulness of combination of culture-dependent techniques and next-generation sequencing techniques both to unravel the microbial patterns and understand the ecological impact of contamination.

Satellite-derived multivariate world-wide lake physical variable timeseries for climate studies.

A consistent dataset of lake surface water temperature, ice cover, water-leaving reflectance, water level and extent is presented. The collection constitutes the Lakes Essential Climate Variable (ECV) for inland waters. The data span combined satellite observations from 1992 to 2020 inclusive and quantifies over 2000 relatively large lakes, which represent a small fraction of the number of lakes worldwide but a significant fraction of global freshwater surface. Visible and near-infrared optical imagery, thermal imagery and microwave radar data from satellites have been exploited. All observations are provided in a common grid at 1/120° latitude-longitude resolution, jointly in daily files. The data/algorithms have been validated against in situ measurements where possible. Consistency analysis between the variables has guided the development of the joint dataset. It is the most complete collection of consistent satellite observations of the Lakes ECV currently available. Lakes are of significant interest to scientific disciplines such as hydrology, limnology, climatology, biogeochemistry and geodesy. They are a vital resource for freshwater supply, and key sentinels for global environmental change.

GLORIA - A globally representative hyperspectral in situ dataset for optical sensing of water quality.

The development of algorithms for remote sensing of water quality (RSWQ) requires a large amount of in situ data to account for the bio-geo-optical diversity of inland and coastal waters. The GLObal Reflectance community dataset for Imaging and optical sensing of Aquatic environments (GLORIA) includes 7,572 curated hyperspectral remote sensing reflectance measurements at 1 nm intervals within the 350 to 900 nm wavelength range. In addition, at least one co-located water quality measurement of chlorophyll a, total suspended solids, absorption by dissolved substances, and Secchi depth, is provided. The data were contributed by researchers affiliated with 59 institutions worldwide and come from 450 different water bodies, making GLORIA the de-facto state of knowledge of in situ coastal and inland aquatic optical diversity. Each measurement is documented with comprehensive methodological details, allowing users to evaluate fitness-for-purpose, and providing a reference for practitioners planning similar measurements. We provide open and free access to this dataset with the goal of enabling scientific and technological advancement towards operational regional and global RSWQ monitoring.

Dissolved organic matter (DOM) quality drives biogeographic patterns of soil bacterial communities and their association networks in semi-arid regions.

It is of great interest to elucidate the biogeographic patterns of soil microorganisms and their driving forces, which is fundamental to predicting alterations in microbial-mediated functions arising from environment changes. Although dissolved organic matter (DOM) represents an important resource for soil microorganisms, knowledge of how its quality affects microbial biogeography is limited. Here, we characterized soil bacterial communities and DOM quality in 45 soil samples collected from a 1500-km sampling transect through semi-arid regions in northern China which are currently suffering great pressure from climate change, using Illumina Miseq sequencing and fluorescence spectroscopy, respectively. We found that DOM quality (i.e. the source of DOM and the humification degree of DOM) had profound shaping influence on the biogeographic patterns exhibited by bacterial diversity, community composition and association networks. Specifically, the composition of bacteria community closely associated with DOM quality. Plant-derived DOM sustained higher bacterial diversity relative to microbial-derived DOM. Meanwhile, bacterial diversity linearly increased with increasing humification degree of DOM. Additionally, plant-derived DOM was observed to foster more complex bacterial association networks with less competition. Together, our work contributes to the factors underlying biogeographic patterns not only of bacterial diversity, community composition but also of their association networks and reports previously undocumented important role of DOM quality in shaping these patterns.

Urbanization altered regional soil organic matter quantity and quality: Insight from excitation emission matrix (EEM) and parallel factor analysis (PARAFAC).

Soil organic matter (SOM) play an important role in soil ecology and global carbon dynamic. As one of the most sever and irreversible land use change, urbanization could alter the regional carbon storage and composition pattern. However how urbanization influence on SOM is still unclear. In this study, we collected soil samples from highly urbanized area of Beijing, China and explore the quantity and quality variations of SOM by using fluorescence spectroscopy in combine with parallel factor analysis (PARAFAC). The results shown that the soil physic-chemical properties were shaped by urbanization. Comparing to nature soil, moisture content, total organic carbon and total nitrogen in urban and rural soil significantly decreased. The fluorescence spectrum demonstrated that SOM quality was also altered by urbanization induced environmental changes. Five fluorescent compounds in SOM was identified by PARAFAC model and three of them was assigned to humic-like substances. The fluorescence intensity of humic-like substances in nature land was significantly higher than of rural and urban land, meanwhile microbial related substance accumulated in urban land in comparison with rural and nature land. The multivariate analyses further reveal the relationship between soil physic-chemical properties and SOM composition. These results suggest that urbanization could not only decrease the SOM quantity but also change the SOM composition. The SOM loss caused by urbanization was mainly consist of humic-like substance loss. Besides urbanization also stimulate the accumulation of microbial related substance in SOM which highlight the importance of microorganism is SOM dynamic.

Increasing aridity affects soil archaeal communities by mediating soil niches in semi-arid regions.

Soil archaea plays a vital role in the functioning of dryland ecosystems, which are expected to expand and get drier in the future as a result of climate change. However, compared with bacteria and fungi, the impacts of increasing aridity on archaea in these ecosystems remain largely unknown. Here, soil samples were collected along a typical aridity gradient in semi-arid regions in Inner Mongolia, China, to investigate whether and how the increasing aridity affects archaeal communities. The results showed that archaeal richness linearly decreased with increasing aridity. After partialling out the effects of soil properties based on partial least squares regression, the significant aridity-richness relationship vanished. The composition of archaeal communities was distributed according to the aridity gradient. These variations were largely driven by the changes in the relative abundance of Thaumarchaeota, Euryarchaeota and unclassified phyla. Niche-based processes were predominant in structuring the observed archaeal aridity-related pattern. The structural equation models further showed that aridity indirectly reduced archaeal richness through improving soil electrical conductivity (EC) and structured community composition by changing soil total nitrogen (TN). These results suggested that soil salinization and N-losses might be important mechanisms underlying the increasing aridity-induced alterations in archaeal communities, and highlighted the importance of soil niches in mediating the indirect impacts of increasing aridity on archaea.

Establishment of stream nutrient criteria by comparing reference conditions with ecological thresholds in a typical eutrophic lake basin.

The establishment of numeric nutrient criteria is essential to aid the control of nutrient pollution and for protecting and restoring healthy ecological conditions. However, it's necessary to determine whether regional nutrient criteria can be defined in stream ecosystems with a poor ecological status. A database of periphytic diatom samples was collected in July and August 2011 and 2012. In total 172 samples were included in the database with matching environmental variables. Here, percentile estimates, nonparametric change-point analysis (nCPA) and Threshold Indicator Taxa ANalysis (TITAN) were conducted to detect the reference conditions and ecological thresholds along a total nitrogen (TN) and total phosphorus (TP) gradient and ammonia nitrogen (NH3-N) for the development of nutrient criteria in the streams of the Lake Dianchi basin. The results highlighted the possibility of establishing regional criteria for nutrient concentrations, which we recommended to be no more than 1.39 mg L-1 for TN, 0.04 mg L-1 for TP and 0.17 mg L-1 for NH3-N to prevent nuisance growths of tolerant taxa, and 0.38 mg L-1 for TN, 0.02 mg L-1 for TP and 0.02 mg L-1 for NH3-N to maintain high quality waters in streams. Additionally, the influence of excessive background nutrient enrichment on the threshold response, and the ecological interaction with other stressors (HQI, etc.) in the nutrient dynamic process need to be considered to establish the eventual nutrient criteria, regardless of which technique is applied.

Bacterioplankton community responses to key environmental variables in plateau freshwater lake ecosystems: A structural equation modeling and change point analysis.

Elevated environmental pressures negatively affect the bacterial community structure. However, little knowledge about the nonlinear responses of spatially related environmental variable across multiple plateau lake ecosystems on bacterioplankton communities has been gathered. Here, we used 454 pyrosequencing of 16S rRNA genes to study the associations of bacterial communities in terms of environmental characteristics as well as the potentially ecological threshold-inducing shifts of the bacterial community structure along the key environmental variables based on hypothesized structural equation models and the SEGMENTED method in 21 plateau lakes. Our results showed that water transparency was the major driving force and that total nitrogen was more significant than total phosphorus in determining the taxon composition of the bacterioplankton community. Significant community threshold estimates for bacterioplankton were observed at 7.36 for pH and 25.6% for the percentage of the agricultural area, while the remarkable change point of the cyanobacteria community structure responding to pH was at 7.74. Furthermore, the findings indicated that increasing nutrient loads can induce a distinct shift in dominance from Proteobacteria to Cyanobacteria, as well as a sharp decrease and adjacent increase when crossing the change point for Actinobacteria and Bacteroidetes along the gradient of the agricultural area.

[A new bioassay model of antibiotic susceptibility by corneofungimetry].

OBJECTIVE: To study the value of a new bioassay model of antibiotic susceptibility by corneofungimetry which is more similar to human internal environment. METHODS: Twenty-one healthy adult volunteers, 12 males and 9 females, aged 32 (22 - 41), were randomly divided into two groups to receive itraconazole 200 mg Bid or 200 mg qd or bid for one week. Stratum corneum strippings were taken from the forearm skin once before administration of itraconazole and 1, 4, 7, 10, 14, 21, 28, and 35 days after administration of itraconazole. Spores of selected fungi (Trichophyton rubrum, T. mentagrophytes, Microsporum canis, Candida albicans, C. glabrata and C. tropicalis) were deposited and cultured on the strippings. PAS stain was used after one-week culture to observe the growth of the fungi by computerized-assisted image analysis to measure the area covered by the yeasts and the dermatophyte. RESULTS: All fungi grew on all the stratum corneum strippings with different numbers of hyphae. The areas covered by hyphae and spores decreased gradually after administration of itraconazole, became the smaller on the seventh day (P = 0.01 or P < 0.01), and began to increased since the 10 th day, and became almost the same sizes as those before the administration of itraconazole on the 35 th day. CONCLUSION: Similar to the human internal environment, corneofungimetry is a useful new model of bioassay for antibiotic susceptibility.

[Fluorescence Properties of Glomalin and Its Relationship with Soil Physyicochemical Characteristics in Different Regions of Beijing City].

Glomalin-related soil proteins (GRSP), which has been used as a presumable biological indicator of soil quality, is of vital ecological importance. In this research, we tested the GRSP content and physicochemical property of soils collected in mountain, urban and suburb areas of Beijing City. Besides, the fluorescence property of GRSP was also studied by using EEM-PARAFAC. The results showed that GRSP could be decomposed into five compounds, terrestrial humic-like substances UVA, terrestrial humic-like substances UVC, oxidized quinones, soil fulvic acid and amino acids. The GRSP content and protein-like fluorescence substances in urban and suburb areas significant decreased and oxidized quinones content elevated in comparison with those in mountain area. The physicochemical property was also shaped by urbanization. Compare to mountain area, moisture content, total organic matters and total nitrogen significantly decreased in urban area soil and suburb area. GRSP content, terrestrial humic-like substances UVA and oxidized quinones content showed significant correlation with soil organic matter and total nitrogen. Base on that, an integrated index system mainly consisting of GRSP concentration and C1 component and C3 component was recommended to evaluate the soil health status.

Cyanobacteria in lakes on Yungui Plateau, China are assembled via niche processes driven by water physicochemical property, lake morphology and watershed land-use.

Plateau lakes are important ecosystems with diverse ecological functions. Cyanobacteria play a key role in plateau lakes as primary producers. However, they are threatening when dense blooms occur. Identifying cyanobacteiral biogeography and the mechanism of assembly processes shaping the distribution of cyanobacteria in plateau lakes is critical for understanding cyanobacterial ecology and applying it to lake management. In the present study, the biogeographic pattern and importance of neutral and niche processes in assembly of cyanobacteria in 21 lakes on Yungui Plateau, China were examined. Results showed that cyanobacteria exhibit unique biogeographic pattern, and most of them have a narrow habitat preference in plateau lakes. They were assembled via niche processes driven by water physicochemical property, lake morphology and watershed land-use, which explained 62.4% of the biological variation. Neutral processes were not at play. Water physicochemical property (key variables - dissolved oxygen, salinity, trophic status and pH) was the most dominant driver shaping its unique biogeographic pattern. Watershed land-use especially urban land, water body and agricultural land also exhibited a strong impact on cyanobacterial distribution, followed by lake morphology. As most of the cyanobacteiral genus detected in these plateau lakes were potential toxin-producers, this study indicated that in order to protect waters from toxic-bloom in the future, reducing nutrient loading and land-use practices are two practical approaches in plateau lake management.