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An aerobic, Gram-stain-negative bacterium, designated as SYSU D00382T, was sourced from soil of Gurbantunggut Desert, PR China. The strain was short-rod-shaped, oxidase-positive and catalase-negative, with yellow-colored, convex, round, and smooth colonies on TSA plate. Growth and proliferation occurred at 4–37 °C (optimal: 28–30 °C), pH 5.0–8.0 (optimal: pH 6.0–7.0) and NaCl concentration of 0–2.5% (optimal: 0–0.5%). The 16S rRNA gene based phylogenetic assessment showed that SYSU D00382T belonged to the genus Pedobacter, and was most closely related to Pedobacter ginsengisoli Gsoil 104T with similarity of 97.7%. The genomic DNA G+C content of SYSU D00382T was 46.4%. The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between SYSU D00382T and P. ginsengisoli Gsoil 104T were 75.7% and 17.5%, respectively. The main polar lipid was phosphatidylethanolamine. The major fatty acids (> 5%) were iso-C15:0, iso-C17:0 3-OH, summed features 3 and 9. The sole respiratory quinone identified was MK-7. The phylogeny based on 16S rRNA gene and whole-genome sequences revealed that SYSU D00382T formed a robust lineage with P. ginsengisoli Gsoil 104T. Based on phenotypic, phylogenetic and genotypic data, a novel specie named Pedobacter deserti sp. nov. is proposed. The type strain is SYSU D00382T (= CGMCC 1.18627T = MCCC 1K04972T = KCTC 82279T). [ABSTRACT FROM AUTHOR]

Conversion of desert soils to cropland may cause changes in some soil properties. The objective of this study was to analyze the effects of converting desert soils to cropland (wheat) and orchard (pistachio) on the soil organic carbon (SOC) content and storage, particulate organic carbon in Abarkooh region (Yazd province). Three land uses included wheat, pistachio, and desert soils were assessed. In order to compare the soil properties in different land uses, In September 2018, soil samples from desert, wheat, and orchard sites were taken from 0–20 and 20–40 cm depths. From each depth, 10 composite soil samples were taken. After pretreatments of soil samples, the soil properties including electrical conductivity, pH, gravel, sand, silt, clay, bulk density, organic carbon, calcium carbonate, were measured according to standard protocols. According to the obtained results, bulk density, gravel content and electrical conductivity decreased after the cultivation of desert soils. The SOC contents in the croplands and orchard were about 3.4-5.8 times higher than those in the desert soils. Also, the results showed an increase of 5.7 to 15.8 times of soil particulate organic carbon in the wheat fields and pistachio orchards compared to desert soils. The lowest SOC storage was observed in desert soils (0.19-0.24 kg.m-2) and the highest was obtained in pistachio orchards (1.08-1.12 kg.m-2). According to the findings of this study, it seems that sustainable cultivation and irrigation of desert soils could be an appropriate method which considerably enhances soil organic carbon sequestration in the study area. [ABSTRACT FROM AUTHOR]

The heterogeneous composition of fungi plays an indispensable role in the foundation of the multifunctionalities of ecosystems within drylands. The precise mechanisms that govern fluctuations in soil fungal assemblages in dryland ecosystems remain incompletely elucidated. In this study, biological soil crusts (biocrusts) at different successional stages in the Gurbantunggut Desert were used as substrates to examine the characteristics and driving factors that influence fungal abundance and community dynamics during biocrust development using qPCR and high-throughput sequencing of the ITS2 region. The findings showed that the physicochemical properties changed significantly with the development of biocrusts. In particular, total nitrogen increased 4.8 times, along with notable increases in ammonium, total phosphorus (2.1 times) and soil organic carbon (6.5 times). Initially, there was a rise in fungal abundance, which was subsequently followed by a decline as the biocrust developed, with the highest abundance detected in lichen crust (2.66×107 copies/g soil) and the lowest in bare sand (7.98×106 copies/g soil). Ascomycetes and Basidiomycetes emerged as dominant phyla, collectively forming 85% of the fungal community. As the biocrust developed, noticeable alterations occurred in fungal community compositions, resulting from changes in the relative proportions of Dothideomycetes, Lecanoromycetes and unclassified ascomycetes. Nitrogen, phosphorus, organic carbon content, and pH of biocrusts were identified as direct or indirect regulators of fungal abundance and community structure. The complexity of fungal networks increased as biocrusts developed as revealed by network analysis, but reduced in the stability of fungal communities within algal and lichen crusts. Keystone species within the fungal community also underwent changes as biocrust developed. These results suggested that shifts in interspecies relationships among fungi could further contribute to the variation in fungal communities during the development of biocrusts. [ABSTRACT FROM AUTHOR]

Due to the misuse of antibiotics, there is an increasing emergence and spread of multidrug-resistant (MDR) bacteria, leading to a human health crisis. To address clinical antibiotic resistance and prevent/control pathogenic microorganisms, the development of novel antibiotics is essential. This also offers a new approach to discovering valuable actinobacterial flora capable of producing natural bioactive products. In this study, we employed bioinformatics and macrogenome sequencing to collect 15 soil samples from three different locations in the Karamay Gobi region. First, we assessed the diversity of microorganisms in soil samples from different locations, analyzing the content of bacteria, archaea, actinomycetes, and fungi. The biodiversity of soil samples from outside the Gobi was found to be higher than that of soil samples from within and in the center of the Gobi. Second, through microbial interaction network analysis, we identified actinomycetes as the dominant group in the system. We have identified the top four antibiotic genes, such as Ecol_fabG_TRC, Efac_liaR_DAP, tetA (58), and macB, by CARD. These genes are associated with peptide antibiotics, disinfecting agents and antiseptics, tetracycline antibiotics, and macrolide antibiotics. In addition, we also obtained 40 other antibiotic-related genes through CARD alignment. Through in-depth analysis of desert soil samples, we identified several unstudied microbial species belonging to different families, including Erythrobacteriaceae, Solirubrobacterales, Thermoleophilaceae, Gaiellaceae, Nocardioidaceae, Actinomycetia, Egibacteraceae, and Acidimicrobiales. These species have the capability to produce peptide antibiotics, macrolide antibiotics, and tetracycline antibiotics, as well as disinfectants and preservatives. This study provides valuable theoretical support for future in-depth research. [ABSTRACT FROM AUTHOR]

One of the most important applications of biotechnology in the food industry is the production of various additives. Among the additives produced by biotechnology method is the production of exopolysaccharides produced by bacteria in dairy products. Diversity in the structure and chemical composition of microbial exopolysaccharides has made them superior to animal and plant polymers. Due to these cases, these compounds can be used as food additives with health effects. In the present study, Bacillus bacteria producing exopolysaccharides were isolated from the soils of desert areas and then, the structural and functional groups of exopolysaccharides were identified using FT-IR method. The presence of peaks in the frequency range 400-4000 (cm-1)indicates the polysaccharide and purity of the extracted material. Then, their effects on the quality of yogurt were investigated. Based on the results, the quality of yogurt samples containing exopolysaccharide of bacteria K, C, B, A and E significantly increased compared to the control group that did not contain exopolysaccharide. Exopolysaccharide from E bacterium significantly reduced hydration compared to other samples and control samples and also significantly increased the viscosity and water holding capacity and consistency of yogurt. Finally, based on the 16S rDNA sequence, the bacterium whose exopolysaccharide had the greatest effect on improving the quality of yogurt, Bacillus wiedmannii strain HBUM207173 was identified. [ABSTRACT FROM AUTHOR]

Soil resistivity is the key parameter influencing resistance and potential distribution on the soil surface for grounding systems and electrodes for HVDC power transmission. The paper presents a novel approach that does not rely on analytical expressions or simplifications inherent in the Wenner and classical characterization methods for obtaining a layered soil model. The new method and corresponding computational tool are implemented as an iterative process using a finite element method coupled with a numerical parameter estimation solver. The novel method is applied on soil with a very thin and highly resistive surface layer compared to a resistivity of a lower layer, where accurate implementation of the classical method would require Wenner measurements for short electrode spacings a. Since the classical characterization methods rely on the assumption that the electrode driving depth b is much smaller than a, it is practically (physically) impossible to drive the electrodes to sufficiently small depth b. The application of the novel method and a comparison with the classical approach are presented on examples including normal soils, one hypothetical soil with a thin highly resistive surface layer, and one experimental desert location. The application of the proposed method leads to an extreme increase in the characterization accuracy for the case of ideal two-layer soil with thin high resistivity topsoil justifying considerable computational time. [ABSTRACT FROM AUTHOR]

Soil characteristics are important indicators of the potential for agricultural production. This study investigates the direct and residual effects of green and farmyard manures on soil dry bulk density, total porosity, soil moisture percentage, infiltration rate and wheat grain yield of a desert plain soil in Northern Sudan during three successive seasons 2007/08 (direct effect), 2008/09 (direct and residual effects) and 2009/10 (residual effect). Treatments consisted of green manure produced from green gram (Vigna radiate) with two seed rates (0 and 12 kg ha-1), and farmyard manure with two levels (0 and 10 ton ha-1) arranged in a split plot design with three replicates. The results revealed that all studied treatments significantly decreased soil bulk density and infiltration rate (P ≤ 0.01), and increased total soil porosity and soil moisture percentage (P≤0.001), as compared to the control in response to the application of the two types of manures. The results also showed that the direct and residual effects of manures caused significant increase in the wheat grain yield of the desert plain soils. It can be concluded that green and farmyard manures had continuing positively effects on the desert plain soil to produce higher grain yield of wheat. Green manure, therefore, may be used in vast desert plain soils areas as it may pose a solution to the problems of the infertility and unavailability of organic manure and farmyard manure may be useful in small areas in the Northern State of Sudan. [ABSTRACT FROM AUTHOR]

The accumulation of heavy metal(loid)s (HMs) in soil-grown mushrooms poses potential health risks. Morchella sextelata (black morel) is a typical soil-grown mushroom with a rapidly expanding cultivation area. This study investigated the distribution of arsenic, cadmium, chromium, copper, mercury, nickel, lead, and zinc in 213 pairs of soil and morel samples collected from 29 provincial administrative regions in China, together with the nutritional contents in the morel samples. The HM contents in the arable soils used to cultivate morels were 2.4–33.1 times higher than those in desert soils, while the HM contents in arable-soil morels were 2.9–155.9 times higher than desert morels. The HM contents of morels and their cultivation soils were significantly correlated (0.465 ≤ R ≤ 0.778, P < 0.001). Furthermore, the enrichment factors of most HMs were higher in arable soils than in desert soils (P < 0.05), except Hg. A considerable proportion of the arable soils produced morels with HMs exceeding the risk control standards (RCSs) for food and the health-risk thresholds of dietary intake. In comparison, HMs in morels from desert soils were far below the RCSs and health-risk thresholds. In addition, desert morels contained higher contents of crude proteins, total polysaccharides, and free amino acids (P < 0.001). These findings indicate that growing morels in desert soils is a way of green production that provides mushroom products with improved safety and nutrition. [Display omitted] • Arable soils had higher HM contents than desert soils. • M. sextelata in arable-soils had higher enrichment factors of HMs than in deserts. • Accumulation of HMs in morel ascocarps showed positive correlations with SOC. • Desert M. sextelata had lower health risks and higher nutritional quality. • M. sextelata cultivation in deserts has stable productivity and high economic profit. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) is a key factor for evaluating soil fertility. Rapidly monitoring organic matter content in desert soil can provide a scientific basis for the rational development and utilization of reserve arable land resources. Although spectral inversion accuracy for SOM under laboratory-controlled conditions is high, it is time-consuming and costly compared to the in situ spectroscopic determination method. However, in situ spectroscopy causes losses in accuracy due to interference from external environmental factors (e.g., the surface roughness of soil, changes in weather conditions, atmospheric water vapor, etc.). Therefore, reducing or removing the interference of external environmental factors to improve the accuracy of in situ spectroscopy for estimating SOM is challenging. In this study, visible and near-infrared (Vis-NIR) in situ spectral data were collected from 135 topsoil (0–20 cm) samples in a desert area of northwestern China, and organic matter content was measured. Three spectral pre-processing methods—the standard normal transform (SNV), reciprocal logarithm (log(1/R)) and normalization (NOR)—combined with three feature variable selection methods—the particle swarm algorithm (PSO), ant colony algorithm (ACO) and simulated annealing (SA) algorithm—were used to filter the spectral feature bands of SOM, and then partial least squares regression (PLSR), a back propagation neural network (BPNN) and a convolutional neural network (CNN) were used to construct the estimation models of SOM. The results indicated that the SNV could enhance the spectral information related to SOM and improve the accuracy of model estimation, and it was one of the most effective spectral pretreatment methods. Compared with the model constructed with the full-band spectroscopy method, the feature variable selection method could effectively improve the estimation accuracy of the Vis-NIR in situ spectroscopy model. The most obvious improvement was found with PSO, where R2 and RPD were improved by more than 0.34 and 0.16, respectively, and RMSE was reduced by more than 0.29 g kg−1. The accuracy of the CNN model was higher than that of the BPNN and PLSR models, both for the inversion model of SOM built from full-band spectral data and the bands selected by the characteristic variable selection method. SNV-PSO-CNN is the optimal hybrid model for in situ spectral measurement of SOM (R2 = 0.71, RPD = 1.88, RMSE = 1.67 g kg−1) and can realize the quantitative in situ spectral inversion of SOM in desert soils. [ABSTRACT FROM AUTHOR]

Phellorinia herculeana is an edible mushroom growing in nutritionally poor and desert soil. There has been little information available about its edaphic and culturing conditions for achieving the vigorous mycelial growth essential for its artificial cultivation, bioaugmentation and biodegradation in unfertile soil. Thus, the present study was conducted to assess its edaphic conditions and find a suitable culturing medium for obtaining maximum growth. It grows commonly in coastal soil with saline conditions, barren land soil unfit for cultivation, and desert soil. It forms a basidiocarp singly around xerophytic trees and annual plants and also in soil without vegetation. In addition to a well-developed pileus and stipe, it has a typical rhizoid that grows horizontally in soil. The rhizoid was thick at the base of the stipe and became thin into the mycelial strand. In our earlier study, we reported that its mycelial growth was very poor on nutrient-rich media containing simple sugar, for example, glucose. In the present study, we observed that cereal-grain-based agar media supported its mycelial growth and among the cereal-grain-based agar media, maize agar medium at the 5% level supported the maximum mycelial growth. Incorporation of glucose into the maize agar medium reduced its mycelial growth compared to its growth on maize agar medium without glucose. Its mycelial growth was at a maximum between 34 °C and 37 °C and at a pH between 7 and 8. Mass multiplication using sand-maize medium prepared at the ratio of 19:1 (sand: maize) supported the maximum mycelial growth. The results of this study would certainly pave a way for the scientific community to develop a protocol for its artificial cultivation and also for its mass multiplication, bioaugmentation and biodegradation in unfertile soil. [ABSTRACT FROM AUTHOR]

Soil nematodes are fundamentally aquatic animals, requiring water to move, feed, and reproduce. Nonetheless, they are ubiquitous in desert soils because they can enter an anhydrobiotic state that allows them to persist when water is biologically unavailable. In the hyper‐arid Namib Desert of Namibia, rain is rare, but fog routinely moves inland from the coast and supports plant and animal life. Very little is understood about how this fog may affect soil organisms. We investigated the role of fog moisture in the ecology of free‐living, soil nematodes across an 87‐km fog gradient in the gravel plains of the Namib Desert. We found that nematodes emerged from anhydrobiosis and became active during a fog event, suggesting that they can utilize fog moisture to survive. Nematode abundance did not differ significantly across the fog gradient and was similar under shrubs and in interplant spaces. Interplant soils harbor biological soil crusts that may sustain nematode communities. As fog declined along the gradient, nematode diversity increased in interplant soils. In areas where fog is rare, sporadic rainfall events can stimulate the germination and growth of desert ephemerals that may have a lasting effect on nematode diversity. In a 30‐day incubation experiment, nematode abundance increased when soils were amended with water and organic matter. However, these responses were not evident in field samples, which show no correlations among nematode abundance, location in the fog gradient, and soil organic matter content. Soil nematodes are found throughout the Namib Desert gravel plains under a variety of conditions. Although shown to be moisture‐ and organic matter‐limited and able to use moisture from the fog for activity, variation in fog frequency and soil organic matter across this unique ecosystem may be biologically irrelevant to soil nematodes in situ. [ABSTRACT FROM AUTHOR]

Abstract Soil nematodes are fundamentally aquatic animals, requiring water to move, feed, and reproduce. Nonetheless, they are ubiquitous in desert soils because they can enter an anhydrobiotic state that allows them to persist when water is biologically unavailable. In the hyper‐arid Namib Desert of Namibia, rain is rare, but fog routinely moves inland from the coast and supports plant and animal life. Very little is understood about how this fog may affect soil organisms. We investigated the role of fog moisture in the ecology of free‐living, soil nematodes across an 87‐km fog gradient in the gravel plains of the Namib Desert. We found that nematodes emerged from anhydrobiosis and became active during a fog event, suggesting that they can utilize fog moisture to survive. Nematode abundance did not differ significantly across the fog gradient and was similar under shrubs and in interplant spaces. Interplant soils harbor biological soil crusts that may sustain nematode communities. As fog declined along the gradient, nematode diversity increased in interplant soils. In areas where fog is rare, sporadic rainfall events can stimulate the germination and growth of desert ephemerals that may have a lasting effect on nematode diversity. In a 30‐day incubation experiment, nematode abundance increased when soils were amended with water and organic matter. However, these responses were not evident in field samples, which show no correlations among nematode abundance, location in the fog gradient, and soil organic matter content. Soil nematodes are found throughout the Namib Desert gravel plains under a variety of conditions. Although shown to be moisture‐ and organic matter‐limited and able to use moisture from the fog for activity, variation in fog frequency and soil organic matter across this unique ecosystem may be biologically irrelevant to soil nematodes in situ.

Humans influence desert ecosystem structure and function by transforming native vegetation into agricultural and non‐agricultural land. However, how different land uses in desert grasslands affect soil phosphorus (P) fractions with varying lability by creating distinct soil physicochemical and microbial properties remains poorly understood. To address this question, a field study was conducted in the arid region of northwestern China, where sites were selected for having an area containing natural desert grassland and three adjacent differently managed land uses converted from desert grassland: 28‐year‐old rainfed shrub (Haloxylon ammodendron) plantation, 35‐year‐old irrigated tree (Populus gansuensis) plantation, and 33‐ to 40‐year‐old irrigated and fertilized croplands. We collected data from four land‐use types for concentrations of soil inorganic and organic P (Pi and Po) fractions of decreasing lability (labile P: resin‐ and NaHCO3‐extractable P; moderately labile P: NaOH‐extractable P; recalcitrant P: HCl‐extractable P and residual P) and edaphic variables as predictors. The relative contributions of individual predictors to variation in P fractions were evaluated using a boosted regression tree analysis. We found significant increases in (1) all P fractions in croplands (77%–418%), with the largest increase in resin‐P; (2) all P fractions except resin‐P in tree plantations (52%–367%), with the largest increase in labile Po; and (3) NaHCO3‐P and HCl‐Pi in shrub plantations (14%–134%), with the largest increase in labile Pi, compared with natural desert grasslands. Edaphic properties dominantly controlled the changes of different P fractions, explaining 51%–93% of the variation in P fractions, but the dominant influential factors differed across P fractions. We conclude that different land uses in desert grassland soil resulted in significant differences in the fractional composition and availability of soil P by affecting edaphic properties differently, informing that soil P cycling can be regulated by altering land‐use types and management levels. Highlights: Assessing the impact of different land uses in desert grasslands on soil P fractions.Different land‐use types showed distinct patterns of soil P dynamics and availability.Soil P responses to land‐use changes were mainly mediated by edaphic properties.The importance of edaphic factors in regulating P dynamics differed among P fractions.Soil P cycling can be regulated by altering land‐use types and management levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nowadays, freshwater crisis seriously challenges human survival and development. • Solar desalination is promising in collecting clean water, but only feasible in regions with available surface water. • Atmospheric water harvesting is independent of surface water but requires high humidity and complex equipments. • In this study, efficient water harvesting from desert soil in very dry regions is achieved via interfacial solar heating under natural sunlight. • The portable and scalable water harvesting device, composed of merely a thin layer of activated carbon, a commercially available polyethylene film and a water container, could collect 1.13 kg of clean water per square meter of desert soil per day. Freshwater crisis seriously challenges human survival and development, especially in arid regions. Solar-driven interfacial evaporation has recently received tremendous interest for collecting clean water, yet is only feasible in regions with available surface water. Atmospheric water harvesting is independent of surface water but requires high RH, additional energy input and complex equipment. Here, we demonstrate efficient water harvesting from desert soil in very dry regions (air RH < 10%, soil moisture content < 3%) via interfacial solar heating under natural sunlight. The water harvesting device, composed of merely a thin layer of activated carbon (for interfacial solar heating on soil surface), a commercially available polyethylene film (for vapor condensation and water transport) and a water container, could collect 1.13 kg of clean water per square meter of desert soil per day (8 h), i.e., 0.53 kg of clean water per kilogram of activated carbon per hour, under a solar flux of 0.26–0.55 kW m−2. Besides, the soil water harvesting system is very portable, low-cost and scalable. This work opens up a new sustainable approach for solving the freshwater crisis in arid and impoverished regions. [ABSTRACT FROM AUTHOR]

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Kitchen waste and wind erosion are two worldwide environmental concerns. This study investigated the feasibility of using kitchen waste for Sporosarcina pasteurii cultivation and its application in wind erosion control of desert soil via microbially induced carbonate precipitation (MICP). Enzymatic hydrolysis was adopted to improve the release and recovery of protein in kitchen waste for subsequent microorganism production. After conditions optimized, the maximum biomass concentration (OD600) and urease activity of Sporosarcina pasteurii in the kitchen waste-based medium reached 4.19, and 14.32 mM urea min−1, respectively, which were comparable to those obtained in conventional standard media. The harvested Sporosarcina pasteurii was then used to catalyze the precipitation of calcium carbonate in the desert soil, and its performance in wind erosion control was evaluated through wind tunnel tests. The microbially mediated calcium carbonate could significantly decrease wind erosion loss of the desert soil even after 12 wet–dry or freeze–thaw cycles. Scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) confirmed the bridge effect of calcium carbonate crystals in the soil matrix. The kitchen waste, as a cost-effective alternative nutrient for bacterial cultivation and carbonate precipitation, showed great potential for large-scale applications in wind erosion control of desert soils. [ABSTRACT FROM AUTHOR]

Background: Quizalofop-p-ethyl (QPE), a unitary R configuration aromatic oxyphenoxypropionic acid ester (AOPP) herbicide, was widely used and had led to detrimental environmental effects. For finding the QPE-degrading bacteria and promoting the biodegradation of QPE, a series of studies were carried out. Results: A QPE-degrading bacterial strain YC-XJ1 was isolated from desert soil and identified as Methylobacterium populi, which could degrade QPE with methanol by cometabolism. Ninety-seven percent of QPE (50 mg/L) could be degraded within 72 h under optimum biodegradation condition of 35°C and pH 8.0. The maximum degradation rate of QPE was 1.4 mg/L/h, and the strain YC-XJ1 exhibited some certain salinity tolerance. Two novel metabolites, 2-hydroxy-6-chloroquinoxaline and quinoxaline, were found by high-performance liquid chromatography/mass spectroscopy analysis. The metabolic pathway of QPE was predicted. The catalytic efficiency of strain YC-XJ1 toward different AOPPs herbicides in descending order was as follows: haloxyfop-p-methyl ≈ diclofop-methyl ≈ fluazifop-p-butyl > clodinafop-propargyl > cyhalofop-butyl > quizalofop-p-ethyl > fenoxaprop-p-ethyl > propaquizafop > quizalofop-p-tefuryl. The genome of strain YC-XJ1 was sequenced using a combination of PacBio RS II and Illumina platforms. According to the annotation result, one α/β hydrolase gene was selected and named qpeh1, for which QPE-degrading function has obtained validation. Based on the phylogenetic analysis and multiple sequence alignment with other QPE-degrading esterases reported previously, the QPEH1 was clustered with esterase family V. Conclusion: M. populi YC-XJ1 could degrade QPE with a novel pathway, and the qpeh1 gene was identified as one of QPE-degrading esterase gene.How to cite: Li X, Wang J, Wu W, et al. Co-metabolic biodegradation of quizalofop-p-ethyl by Methylobacterium populi YC-XJ1 and identification of QPEH1 esterase. Electron J Biotechnol 2020;46. https://doi.org/10.1016/j.ejbt.2020.05.003.

Two Gram-stain-negative, aerobic, milk-white coloured, non-motile, short rod-shaped bacteria, designated as strains SYSU D60010 T and SYSU D60012 T , were isolated from sand samples collected from the Taklimakan Desert of Xinjiang Province in China. Both strains were positive for oxidase, catalase and nitrate reduction, but negative for amylase, H 2 S production, hydrolysis of gelatin and cellulase. Strains SYSU D60010 T and SYSU D60012 T grew well at 28 °C, at pH 7 and had the same NaCl tolerance range of 0-1 % (w/v). The major fatty acids (>5 %) of strains SYSU D60010 T and SYSU D60012 T were summed feature 8 (C 18 : 1  ω 7 c and/or C 18 : 1  ω 6 c ), iso-C 19 : 0 cyclo ω 8 c , C 16 : 0 and iso-C 18 : 1 2-OH. Q-10 was the only respiratory ubiquinone. Strains SYSU D60010 T and SYSU D60012 T showed high 16S rRNA gene sequence similarities to Aestuariivirga litoralis SYSU M10001 T (94.2 and 94.1 %), Rhodoligotrophos jinshengii BUT-3 T (92.0 and 91.9 %) and Rhodoligotrophos appendicifer 120-1 T (91.8 and 91.7 %), and the genomes were 7.4 and 5.8 Mbp in size with DNA G+C contents of 62.8 and 63.0 mol%, respectively. Phylogenetic, phenotypic and chemotaxonomic characteristics indicated that these two strains represent a novel genus and two novel species within the family Aestuariivirgaceae . We propose the name Taklimakanibacter deserti gen. nov., sp. nov. for strain SYSU D60010 T , representing the type strain of this species (=KCTC 52783 T =NBRC 113344 T ) and Taklimakanibacter lacteus gen. nov., sp. nov. for strain SYSU D60012 T , representing the type strain of this species (=KCTC 52785 T =NBRC 113128 T ).

The diel dynamic of the CO2 concentration in soils in relation to temperature is not yet fully understood. Air temperature might control the soil CO2 concentration due to thermal convective venting at sites experiencing large temperature differences between the atmosphere and the soil. Therefore, the objective of this study was to determine the soil CO2 concentration and its temporal dynamic in a deep desert soil in relationship to soil and air temperature based on high frequency measurements. For this purpose, CO2 concentration and temperature were measured in six soil depths (ranging from 15 to 185 cm) in a coarse-textured desert soil in the North of Chile every 60 min together with precipitation and air temperature for one year. The mean CO2 concentration calculated across the whole measuring period increased linearly with soil depth from 463 ppm in 15 cm to 1542 ppm in 185 cm depth. We observed a strong diel oscillation of the CO2 concentration that decreased with soil depth and a hysteretic relationship between the topsoil CO2 concentration and both air and soil temperature. The Rayleigh-Darcy number calculated for different times indicates that thermal convective venting of the soil occurred during the night and in the early morning. A small precipitation event (4 mm) increased the CO2 concentrations in 15, 30, and 50 cm depths for several days but did not alter the amplitude of the diel oscillation of the CO2 concentration. The diel oscillation of the CO2 concentration and the hysteretic relationship between soil CO2 concentration and air temperature were likely caused by thermal convection, leading to transport of CO2-rich air from the soil to the atmosphere at night. In conclusion, our results indicate that the soil CO2 concentration can be largely controlled by convection caused by temperature differences, and not only by diffusion. The results have important implications as they provide further evidence that thermal convective venting contributes to gas exchange at sites experiencing large temperature differences between the atmosphere and the soil, which is relevant for soil chemical reactions. [ABSTRACT FROM AUTHOR]

A petroleum hydrocarbon degrading bacterium Rhodococcus erythropolis KB1 was used to investigate the bioremediation efficiency of the petroleum contaminated desert steppe soils. The total petroleum hydrocarbons (TPHs) removal efficiency in the soils was analyzed with different treatments including natural degradation, bioaugmentation with R. erythropolis cells, biostimulation with nitrogen and phosphorus, and a combination of bioaugmentation and biostimulation. The petroleum contaminated soils were separately inoculated with R. erythropolis cells, nitrogen and phosphorus nutrients, a combination of the bacterial cells and the nutrients. The soil samples were kept at room temperature for 115 days of bioremediation. On the 66th day, the soil samples were strengthened with the same treatments. The results showed that the degradation rate of the natural degradation group was 20.20%. The biodegradation rates of the bioaugmentation group and biostimulation group were 36.02 and 40.10%, respectively. The combination group of bioaugmentation and biostimulation was the most effective way to remediate petroleum-contaminated soils with a degradation rate of 43.89%. In the bioremediation process the saturated hydrocarbons, especially the linear alkanes were the most easily degraded petroleum components. The cultivable bacterial counts of the soils were significantly increased in the bioaugmentation, biostimulation, and combined groups with bioaugmentation and biostimulation. The bacterial diversities of the petroleum contaminated desert steppe soil changed greatly when compared with that of the natural desert steppe soil. The bacterial structure and abundance of the soils in different treatments also changed significantly. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) is a key factor for evaluating soil fertility. Rapidly monitoring organic matter content in desert soil can provide a scientific basis for the rational development and utilization of reserve arable land resources. Although spectral inversion accuracy for SOM under laboratory-controlled conditions is high, it is time-consuming and costly compared to the in situ spectroscopic determination method. However, in situ spectroscopy causes losses in accuracy due to interference from external environmental factors (e.g., the surface roughness of soil, changes in weather conditions, atmospheric water vapor, etc.). Therefore, reducing or removing the interference of external environmental factors to improve the accuracy of in situ spectroscopy for estimating SOM is challenging. In this study, visible and near-infrared (Vis-NIR) in situ spectral data were collected from 135 topsoil (0–20 cm) samples in a desert area of northwestern China, and organic matter content was measured. Three spectral pre-processing methods—the standard normal transform (SNV), reciprocal logarithm (log(1/R)) and normalization (NOR)—combined with three feature variable selection methods—the particle swarm algorithm (PSO), ant colony algorithm (ACO) and simulated annealing (SA) algorithm—were used to filter the spectral feature bands of SOM, and then partial least squares regression (PLSR), a back propagation neural network (BPNN) and a convolutional neural network (CNN) were used to construct the estimation models of SOM. The results indicated that the SNV could enhance the spectral information related to SOM and improve the accuracy of model estimation, and it was one of the most effective spectral pretreatment methods. Compared with the model constructed with the full-band spectroscopy method, the feature variable selection method could effectively improve the estimation accuracy of the Vis-NIR in situ spectroscopy model. The most obvious improvement was found with PSO, where R2 and RPD were improved by more than 0.34 and 0.16, respectively, and RMSE was reduced by more than 0.29 g kg−1. The accuracy of the CNN model was higher than that of the BPNN and PLSR models, both for the inversion model of SOM built from full-band spectral data and the bands selected by the characteristic variable selection method. SNV-PSO-CNN is the optimal hybrid model for in situ spectral measurement of SOM (R2 = 0.71, RPD = 1.88, RMSE = 1.67 g kg−1) and can realize the quantitative in situ spectral inversion of SOM in desert soils.

[Display omitted] • Microbial-induced calcite precipitation studied for wind erosion control of loess. • Native ureolytic bacteria stimulated by spraying of treatment media on loess. • Differences in media concentration impact the enrichment of calcite in soils. • Shifts in microbial abundance and diversity depend on media concentration. • Biotic and abiotic processes lead to major differences in soil desiccation cracking. Microbial-induced calcite precipitation (MICP) is a soil amelioration technique that addresses various environmental and engineering concerns. Here, we present a study focusing on aeolian erosion control of loess soil from the Negev Desert (Israel). Changes in the treated soil's chemical, physical, and microbial community (abundance and diversity) were characterized following bio-stimulation of native, urea-hydrolyzing soil bacteria to achieve MICP. Bio-stimulation of the loess soil was induced in liquid media (batch experiments) and by spraying soil trays with stimulation media (urea and yeast extract). These experiments showed that the Negev loess could be readily stimulated to induce bacterial urea hydrolysis. Three to four daily sprayings were sufficient to achieve effective bio-stimulation, evidenced by a high hydrolysis rate and an alkaline pH. Erodibility experiments on a decimeter scale (50 cm x 50 cm trays) were performed on loess sprayed with treatment media with varying concentrations of urea and CaCl2, with a constant 1:1 M ratio. The effectiveness of the treatments was studied in a wind tunnel and by image analysis of desiccation cracks. Upscaling of the experiments to the large trays revealed a more complicated reality with urease activity, community composition, and calcium carbonate precipitation depending on the concentration of the treatment medium. Specifically, we show that a twofold reduction in the area and length of the desiccation cracks can be achieved by spraying the soil with a 0.5 M solution, resulting in effective MICP or a high concentration treatment (>1M solution) without achieving MICP. Our results show that erosion mitigation in loess soil depends on an interplay between biotic and abiotic processes based on the treatment media concentration and provides a necessary step for upscaling the bio-stimulated MICP strategy for future field implementations. [ABSTRACT FROM AUTHOR]

The heterogeneous composition of fungi plays an indispensable role in the foundation of the multifunctionalities of ecosystems within drylands. The precise mechanisms that govern fluctuations in soil fungal assemblages in dryland ecosystems remain incompletely elucidated. In this study, biological soil crusts (biocrusts) at different successional stages in the Gurbantunggut Desert were used as substrates to examine the characteristics and driving factors that influence fungal abundance and community dynamics during biocrust development using qPCR and high-throughput sequencing of the ITS2 region. The findings showed that the physicochemical properties changed significantly with the development of biocrusts. In particular, total nitrogen increased 4.8 times, along with notable increases in ammonium, total phosphorus (2.1 times) and soil organic carbon (6.5 times). Initially, there was a rise in fungal abundance, which was subsequently followed by a decline as the biocrust developed, with the highest abundance detected in lichen crust (2.66 × 10 7 copies/g soil) and the lowest in bare sand (7.98 × 10 6 copies/g soil). Ascomycetes and Basidiomycetes emerged as dominant phyla, collectively forming 85% of the fungal community. As the biocrust developed, noticeable alterations occurred in fungal community compositions, resulting from changes in the relative proportions of Dothideomycetes, Lecanoromycetes and unclassified ascomycetes. Nitrogen, phosphorus, organic carbon content, and pH of biocrusts were identified as direct or indirect regulators of fungal abundance and community structure. The complexity of fungal networks increased as biocrusts developed as revealed by network analysis, but reduced in the stability of fungal communities within algal and lichen crusts. Keystone species within the fungal community also underwent changes as biocrust developed. These results suggested that shifts in interspecies relationships among fungi could further contribute to the variation in fungal communities during the development of biocrusts., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Liu, Zhou, Zhang, Zhao, Wang, Li and Zhang.)

Two novel bacterial strains, designated as SYSU D00823 T and SYSU D00873 T , were isolated from sandy soil of the Gurbantunggut Desert in Xinjiang, north-west China. SYSU D00823 T and SYSU D00873 T shared 99.0 % 16S rRNA gene sequence identity, and were both most closely related to Pedobacter xinjiangensis 12157 T with 96.1 % and 96.0 % similarities, respectively. Phylogenetic and phylogenomic analyses revealed that the two isolates and P. xinjiangensis 12157 T formed a separate distinct cluster in a stable subclade with the nearby species Pedobacter mongoliensis 1-32 T , as well as the genera Pararcticibacter and Arcticibacter . Furthermore, P. mongoliensis 1-32 T formed a separate deep-branching lineage and did not form a cluster with members of the genus Pedobacter . The average nucleotide identity and digital DNA-DNA hybridization values between SYSU D00823 T and SYSU D00873 T and related species were well below the thresholds for species delineation (<81.0 % and <24.0 %, respectively). The genomes of SYSU D00823 T and SYSU D00873 T were 6.19 and 6.43 Mbp in size with 40.4 % and 40.5 % DNA G+C contents, respectively. The predominant fatty acids (>10 %) of SYSU D00823 T and SYSU D00873 T were iso-C 15 : 0 , iso-C 17 : 0 3-OH and summed feature 3 (C 16 : 1 ω 7 c and/or C 16 : 1 ω 6 c ). Menaquinone-7 was the only respiratory quinone. The major polar lipids were phosphatidylethanolamine, glycosphingolipid, aminoglycolipid/glycolipid, aminophospholipid and three or four unidentified polar lipids. These data indicated that strains SYSU D00823 T and SYSU D00873 T should be assigned to two novel species of a new genus within the family Sphingobacteriaceae , for which the names Desertivirga arenae gen. nov., sp. nov. and Desertivirga brevis sp. nov. are proposed. The type strains are SYSU D00823 T (=CGMCC 1.18630 T =MCCC 1K04973 T =KCTC 82278 T ) and SYSU D00873 T (=CGMCC 1.18629 T =MCCC 1K04974 T =KCTC 82281 T ), respectively. Accordingly, the reclassification of P. xinjiangensis as Desertivirga xinjiangensis comb. nov., and P. mongoliensis as Paradesertivirga mongoliensis gen. nov., comb. nov. are also proposed.

Desert environments constitute one of the largest and yet most fragile ecosystems on Earth. Under the absence of regular precipitation, microorganisms are the main ecological component mediating nutrient fluxes by using soil components, like minerals and salts, and atmospheric gases as a source for energy and water. While most of the previous studies on microbial ecology of desert environments have focused on surface environments, little is known about microbial life in deeper sediment layers. Our study is extending the limited knowledge about microbial communities within the deeper subsurface of the hyperarid core of the Atacama Desert. By employing intracellular DNA extraction and subsequent 16S rRNA sequencing of samples collected from a soil pit in the Yungay region of the Atacama Desert, we unveiled a potentially viable microbial subsurface community residing at depths down to 4.20 m. In the upper 80 cm of the playa sediments, microbial communities were dominated by Firmicutes taxa showing a depth-related decrease in biomass correlating with increasing amounts of soluble salts. High salt concentrations are possibly causing microbial colonization to cease in the lower part of the playa sediments between 80 and 200 cm depth. In the underlying alluvial fan deposits, microbial communities reemerge, possibly due to gypsum providing an alternative water source. The discovery of this deeper subsurface community is reshaping our understanding of desert soils, emphasizing the need to consider subsurface environments in future explorations of arid ecosystems., (© The Author(s) 2024. Published by Oxford University Press on behalf of National Academy of Sciences.)

Due to the misuse of antibiotics, there is an increasing emergence and spread of multidrug-resistant (MDR) bacteria, leading to a human health crisis. To address clinical antibiotic resistance and prevent/control pathogenic microorganisms, the development of novel antibiotics is essential. This also offers a new approach to discovering valuable actinobacterial flora capable of producing natural bioactive products. In this study, we employed bioinformatics and macro-genome sequencing to collect 15 soil samples from three different locations in the Karamay Gobi region. First, we assessed the diversity of microorganisms in soil samples from different locations, analyzing the content of bacteria, archaea, actinomycetes, and fungi. The biodiversity of soil samples from outside the Gobi was found to be higher than that of soil samples from within and in the center of the Gobi. Second, through microbial interaction network analysis, we identified actinomycetes as the dominant group in the system. We have identified the top four antibiotic genes, such as Ecol&#95;fabG&#95;TRC , Efac&#95;liaR&#95;DAP , tet A (58), and mac B, by CARD. These genes are associated with peptide antibiotics, disinfecting agents and antiseptics, tetracycline antibiotics, and macrolide antibiotics. In addition, we also obtained 40 other antibiotic-related genes through CARD alignment. Through in-depth analysis of desert soil samples, we identified several unstudied microbial species belonging to different families, including Erythrobacteriaceae , Solirubrobacterales , Thermoleophilaceae , Gaiellaceae , Nocardioidaceae , Actinomycetia , Egibacteraceae , and Acidimicrobiales . These species have the capability to produce peptide antibiotics, macrolide antibiotics, and tetracycline antibiotics, as well as disinfectants and preservatives. This study provides valuable theoretical support for future in-depth research., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yang, Zhang, Yang, Feng, Li, Li and Liu.)

Microbial-induced calcite precipitation (MICP) is a soil amelioration technique aiming to mitigate different environmental and engineering concerns, including desertification, soil erosion, and soil liquefaction, among others. The hydrolysis of urea, catalyzed by the microbial enzyme urease, is considered the most efficient microbial pathway for MICP. Biostimulated MICP relies on the enhancement of indigenous urea-hydrolyzing bacteria by providing an appropriate enrichment and precipitation medium, as opposed to bioaugmentation, which requires introducing large volumes of exogenous bacterial cultures into the treated soil along with a growth and precipitation medium. Biostimulated MICP in desert soils is challenging as the total carbon content and the bacterial abundance are considerably low. In this study, we examined the biostimulation potential in soils from the Negev Desert, Israel, for the purpose of mitigation of topsoil erosion in arid environments. Incubating soil samples in urea and enrichment media demonstrated effective urea hydrolysis leading to pH increase, which is necessary for calcite precipitation. Biostimulation rates were found to increase with concentrations of energy (carbon) source in the stimulation media, reaching its maximal levels within 3 to 6 days. Following stimulation, calcium carbonate precipitation was induced by spiking stimulated bacteria in precipitation (CaCl2 enriched) media. The results of our research demonstrate that biostimulated MICP is feasible in the low-carbon, mineral soils of the northern Negev Desert in Israel. [ABSTRACT FROM AUTHOR]

The Namib Desert is one of the world's only truly coastal desert ecosystem. Until the end of the 1st decade of the twenty-first century, very little was known of the microbiology of this southwestern African desert, with the few reported studies being based solely on culture-dependent approaches. However, from 2010, an intense research program was undertaken by researchers from the University of the Western Cape Institute for Microbial Biotechnology and Metagenomics, and subsequently the University of Pretoria Centre for Microbial Ecology and Genomics, and their collaborators, led to a more detailed understanding of the ecology of the indigenous microbial communities in many Namib Desert biotopes. Namib Desert soils and the associated specialized niche communities are inhabited by a wide array of prokaryotic, lower eukaryotic and virus/phage taxa. These communities are highly heterogeneous on both small and large spatial scales, with community composition impacted by a range of macro- and micro-environmental factors, from water regime to soil particle size. Community functionality is also surprisingly non-homogeneous, with some taxa retaining functionality even under hyper-arid soil conditions, and with subtle changes in gene expression and phylotype abundances even on diel timescales. Despite the growing understanding of the structure and function of Namib Desert microbiomes, there remain enormous gaps in our knowledge. We have yet to quantify many of the processes in these soil communities, from regional nutrient cycling to community growth rates. Despite the progress that has been made, we still have little knowledge of either the role of phages in microbial community dynamics or inter-species interactions. Furthermore, the intense research efforts of the past decade have highlighted the immense scope for future microbiological research in this dynamic, enigmatic and charismatic region of Africa. [ABSTRACT FROM AUTHOR]

The mechanism and environmental controls on soil hydrogen (H2) uptake are not well understood but are essential for understanding the atmospheric H2 budget. Field observations of soil H2 uptake are limited, and here we present the results from a series of measurements in forest, desert, and marsh ecosystems in southern California. We measured soil H2 fluxes using flux chambers from September 2004 to July 2005. Mean H2 flux rates and standard deviations were −7.9 + −4.2, −7.6 + −5.3 and −7.5 + −3.4 nmol m−2 s−1 for the forest, desert, and marsh, respectively (corresponding to deposition velocities of 0.063 + −0.029, 0.051 + −0.036, 0.035 + −0.013 cm s−1). Soil profile measurements showed that H2 mixing ratios were between 3% and 51% of atmospheric levels at 10 cm and that the penetration of H2 into deeper soil layers increased with soil drying. Soil removal experiments in the forest demonstrated that the litter layer did not actively consume H2, the removal of this layer increased uptake by deeper soil layers, and the exposure of subsurface soil layers to ambient atmospheric H2 levels substantially increased their rate of uptake. Similar soil removal experiments at the desert site showed that extremely dry surface soils did not consume H2 and that fluxes at the surface increased when these inactive layers were removed. We present a model of soil H2 fluxes and show that the diffusivity of soils, along with the vertical distribution of layers that actively consume H2 regulate surface fluxes. We found that soil organic matter, CO2 fluxes, and ecosystem type were not strong controllers of H2 uptake. Our experiments highlight H2 diffusion into soils as an important limit on fluxes and that minimum moisture level is needed to initiate microbial uptake.

Algeria is the largest country in Africa characterized by semi-arid and arid sites, located in the North, and hypersaline zones in the center and South of the country. Several autochthonous plants are well known as medicinal plants, having in common tolerance to aridity, drought and salinity. In their natural environment, they live with a great amount of microbial species that altogether are indicated as plant microbiota, while the plants are now viewed as a “holobiont”. In this work, the microbiota of the soil associated to the roots of fourteen economically relevant autochthonous plants from Algeria have been characterized by an innovative metagenomic approach with a dual purpose: (i) to deepen the knowledge of the arid and semi-arid environment and (ii) to characterize the composition of bacterial communities associated with indigenous plants with a strong economic/commercial interest, in order to make possible the improvement of their cultivation. The results presented in this work highlighted specific signatures which are mainly determined by climatic zone and soil properties more than by the plant species.

Temperature is an important factor regulating the production of the greenhouse gas CH4. Structure and function of the methanogenic microbial communities are often drastically different upon incubation at 45°C versus 25°C or 35°C, but are also different in different soils. However, the extent of taxonomic redundancy within each functional group and the existence of different temperature-dependent microbial community network modules are unknown. Therefore, we investigated paddy soils from Italy and the Philippines and a desert soil from Utah (United States), which all expressed CH4 production upon flooding and exhibited structural and functional differences upon incubation at three different temperatures. We continued incubation of the pre-incubated soils (Liu et al., 2018) by changing the temperature in a factorial manner. We determined composition, abundance and function of the methanogenic archaeal and bacterial communities using HiSeq Illumina sequencing, qPCR and analysis of activity and stable isotope fractionation, respectively. Heatmap analysis of operational taxonomic units (OTU) from the different incubations gave detailed insights into the community structures and their putative functions. Network analysis showed that the microbial communities in the different soils were all organized within modules distinct for the three incubation temperatures. The diversity of Bacteria and Archaea was always lower at 45°C than at 25 or 35°C. A shift from 45°C to lower temperatures did not recover archaeal diversity, but nevertheless resulted in the establishment of structures and functions that were largely typical for soil at moderate temperatures. At 25 and 35°C and after shifting to one of these temperatures, CH4 was always produced by a combination of acetoclastic and hydrogenotrophic methanogenesis being consistent with the presence of acetoclastic (Methanosarcinaceae, Methanotrichaceae) and hydrogenotrophic (Methanobacteriales, Methanocellales, Methanosarcinaceae) methanogens. At 45°C, however, or after shifting from moderate temperatures to 45°C, only the Philippines soil maintained such combination, while the other soils were devoid of acetoclastic methanogens and consumed acetate instead by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis. Syntrophic acetate oxidation was apparently achieved by Thermoanaerobacteraceae, which were especially abundant in Italian paddy soil and Utah desert soil when incubated at 45°C. Other bacterial taxa were also differently abundant at 45°C versus moderate temperatures, as seen by the formation of specific network modules. However, the archaeal OTUs with putative function in acetoclastic or hydrogenotrophic methanogenesis as well as the bacterial OTUs were usually not identical across the different soils and incubation conditions, and if they were, they suggested the existence of mesophilic and thermophilic ecotypes within the same OTUs. Overall, methanogenic function was determined by the bacterial and/or archaeal community structures, which in turn were to quite some extent determined by the incubation temperature, albeit largely individually in each soil. There was quite some functional redundancy as seen by different taxonomic community structures in the different soils and at the different temperatures.

Sediments in the hyper-arid core of the Atacama Desert are a terrestrial analog to Mars regolith. Understanding the distribution and drivers of microbial life in the sediment may give critical clues on how to search for biosignatures on Mars. Here, we identify the spatial distribution of highly specialized bacterial communities in previously unexplored depth horizons of subsurface sediments to a depth of 800 mm. We deployed an autonomous rover in a mission-relevant Martian drilling scenario with manual sample validation. Subsurface communities were delineated by depth related to sediment moisture. Geochemical analysis indicated soluble salts and minerology that influenced water bio-availability, particularly in deeper sediments. Colonization was also patchy and uncolonized sediment was associated with indicators of extreme osmotic challenge. The study identifies linkage between biocomplexity, moisture and geochemistry in Mars-like sediments at the limit of habitability and demonstrates feasibility of the rover-mounted drill for future Mars sample recovery.

Previous studies have observed a negative CO 2 efflux from semi-desert and desert soil, but the carbon uptake in alkaline soils has not been measured quantitatively in laboratory. The present study aims at closing this gap considering the effect of temperature, soil pH and pCO 2. CO 2 uptake was studied with the help of the Barometric Process Separation (BaPS) technique. CO 2 uptake was studied at 3 different temperatures viz. 15, 20 and 25 °C. CO 2 uptake was observed after CO 2 injection with pH values ranging from 8 to 10 in desert Solonchak soils. We found that CO 2 uptake depended on pCO 2 and temperature. CO 2 uptake occurred rapidly within the first 10 min after the CO 2 injection and gradually slowed down afterwards. Results showed that 72%–97% of injected CO 2 was taken up by soils (pH 8–10). CO 2 uptake increased as soil pH increased and its uptake reached equilibrium faster in soil with a lower pH level (pH < 9) than in soil with a higher pH level (pH ≥ 9). Dissolved CO 2 (CO 2aq) (μmol ml−1) increased with increasing CO 2 partial pressure (pCO 2) with equation y = a (1-bx) (r2 > 0.96) and pH. The lower temperature produced a higher CO 2aq for the same pCO 2 value. In conclusion, desert soils can rapidly uptake of CO 2 , and the main controlling process of CO 2 uptake in the desert soils was decided by soil pH and temperature. The CO 2 uptake by the soil solution may be an important pathway for C sequestration in semi-desert and desert regions. • Soil CO 2 uptake increased with increased soil pH and pCO 2 and decreased temperature. • Soil CO 2 uptake reached equilibrium faster in lower pH soil than higher pH soil. • The CO 2 uptake of desert soils were fast within 10 min. • The CO 2 uptake by the soil solution may be an important pathway for C sequestration in semi-desert and desert regions. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study was to investigate the effects of amendment of different biochars on the physical and hydraulic properties of desert soil. Materials and methods: Biochars were produced with woodchip, rice straw, and dairy manure at temperatures of 300 and 700 °C, respectively. Each biochar at 5% (w/w) was mixed with desert soil, and the mixtures were incubated for 120 days. Results and discussion: The different biochar treatments greatly reduced soil bulk density and saturated hydraulic conductivity. Especially the rice straw biochar addition resulted in the lowest saturated hydraulic conductivities among the treatments. Biochar addition significantly increased water retention of desert soil at any suction. At the same suction and experimental time, the treatment with the rice straw biochar produced at the lower temperature resulted in higher water content than the other treatments. The biochar additions slightly enhanced formation of soil macro-aggregates in the early experimental time. However, the aggregate contents gradually decreased with time due to the lack of effective binding agents (e.g., soil organic matter and clay minerals). Conclusions: The changes of hydraulic properties of desert soil were attributable to the biochar properties. The higher fine particle content, porosity, and surface hydrophilicity of rice straw biochars were the most beneficial properties to increase soil water retention and to reduce water flow in the desert soil. The improvement of hydraulic properties by biochar addition may provide a potential solution to combat desertification. [ABSTRACT FROM AUTHOR]

Based on the environmental characteristics of Gurbantunggut Desert in Xinjiang, the mechanical properties and durability of desert soil compaction test, dry and wet cycle test and freeze-thaw cycle test were studied. The results show that the curing agent of the optimal alkali slag powder in solidified desert soil is 14%, and the optimum water content is 10%, at which time the maximum density is 2.09 g/cm3 and 28 d compressive strength is 6.34 MPa. The compressive strength of 28 d without lateral limit of cured desert soil increases with the increase of the number of dry and wet cycles, and when the number of dry and wet cycles reaches 9 times, the compressive strength of the non-lateral limit decreases gradually, at this time the maximum strength is 8.67 MPa, which is 27.9% lower than that of the standard specimen. The compressive strength of the solidified desert soil increases with the increase of the number of freeze-thaw cycles, and when the freeze-thaw cycle is 5 times, the increase tends to be flat, and when the number of freeze-thaw cycles reaches 7 times, the intensity decreases gradually with the increase of age, and the strength after 9 times freeze-thaw cycles is 7.8 MPa, which is 80.4% of the standard specimen. [ABSTRACT FROM AUTHOR]

Temperature is an important factor regulating the production of the greenhouse gas CH4. Structure and function of the methanogenic microbial communities are often drastically different upon incubation at 45°C versus 25°C or 35°C, but are also different in different soils. However, the extent of taxonomic redundancy within each functional group and the existence of different temperature-dependent microbial community network modules are unknown. Therefore, we investigated paddy soils from Italy and the Philippines and a desert soil from Utah (United States), which all expressed CH4 production upon flooding and exhibited structural and functional differences upon incubation at three different temperatures. We continued incubation of the pre-incubated soils (Liu et al., 2018) by changing the temperature in a factorial manner. We determined composition, abundance and function of the methanogenic archaeal and bacterial communities using HiSeq Illumina sequencing, qPCR and analysis of activity and stable isotope fractionation, respectively. Heatmap analysis of operational taxonomic units (OTU) from the different incubations gave detailed insights into the community structures and their putative functions. Network analysis showed that the microbial communities in the different soils were all organized within modules distinct for the three incubation temperatures. The diversity of Bacteria and Archaea was always lower at 45°C than at 25 or 35°C. A shift from 45°C to lower temperatures did not recover archaeal diversity, but nevertheless resulted in the establishment of structures and functions that were largely typical for soil at moderate temperatures. At 25 and 35°C and after shifting to one of these temperatures, CH4 was always produced by a combination of acetoclastic and hydrogenotrophic methanogenesis being consistent with the presence of acetoclastic (Methanosarcinaceae , Methanotrichaceae) and hydrogenotrophic (Methanobacteriales , Methanocellales , Methanosarcinaceae) methanogens. At 45°C, however, or after shifting from moderate temperatures to 45°C, only the Philippines soil maintained such combination, while the other soils were devoid of acetoclastic methanogens and consumed acetate instead by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis. Syntrophic acetate oxidation was apparently achieved by Thermoanaerobacteraceae , which were especially abundant in Italian paddy soil and Utah desert soil when incubated at 45°C. Other bacterial taxa were also differently abundant at 45°C versus moderate temperatures, as seen by the formation of specific network modules. However, the archaeal OTUs with putative function in acetoclastic or hydrogenotrophic methanogenesis as well as the bacterial OTUs were usually not identical across the different soils and incubation conditions, and if they were, they suggested the existence of mesophilic and thermophilic ecotypes within the same OTUs. Overall, methanogenic function was determined by the bacterial and/or archaeal community structures, which in turn were to quite some extent determined by the incubation temperature, albeit largely individually in each soil. There was quite some functional redundancy as seen by different taxonomic community structures in the different soils and at the different temperatures. [ABSTRACT FROM AUTHOR]

Sediments in the hyper-arid core of the Atacama Desert are a terrestrial analog to Mars regolith. Understanding the distribution and drivers of microbial life in the sediment may give critical clues on how to search for biosignatures on Mars. Here, we identify the spatial distribution of highly specialized bacterial communities in previously unexplored depth horizons of subsurface sediments to a depth of 800 mm. We deployed an autonomous rover in a mission-relevant Martian drilling scenario with manual sample validation. Subsurface communities were delineated by depth related to sediment moisture. Geochemical analysis indicated soluble salts and minerology that influenced water bio-availability, particularly in deeper sediments. Colonization was also patchy and uncolonized sediment was associated with indicators of extreme osmotic challenge. The study identifies linkage between biocomplexity, moisture and geochemistry in Mars-like sediments at the limit of habitability and demonstrates feasibility of the rover-mounted drill for future Mars sample recovery. [ABSTRACT FROM AUTHOR]

A novel actinomycete, designated strain YIM CF22T, was isolated from a desert soil sample collected from Turpan in Xinjiang Uyghur Autonomous Region, north-western China. The taxonomic position of the strain YIM CF22T is described based on a polyphasic approach. Strain YIM CF22T was found to form irregular sporangia on agar media. It contains meso-diaminopimelic acid in the cell wall peptidoglycan. The major menaquinone was identified as MK-9(H4); the polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, two unidentified phospholipids and two unidentified glycolipids. The whole cell sugars were found to be ribose, mannose, galactose, glucose and xylose. The major cellular fatty acids were found to be (> 5%) iso-C16:0 (43.5%), anteiso-C17:0 (10.2%), iso-C15:0 (7.1%), C17:1ω8c (6.3%) and iso H-C16:1 (5.9%). The G+C content was determined to be 70.8%. 16S rRNA gene sequence analysis of strain YIM CF22T showed high similarity (97.0%) to Actinoplanes rishiriensis NBRC 108556T. The strain also showed high 16S rRNA gene sequence similarities to Verrucosispora sediminis CGMCC 4.3550T (96.9%) and Micromonospora tulbaghiae DSM 45142T (96.8%). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain YIM CF22T clusters with A. rishiriensis NBRC 108556T, Actinoplanes globisporus JCM 3186T and Actinoplanes rhizophilus NEAU-A-2T. Based on the differential phenotypic characteristics and the results of DNA-DNA relatedness and phylogenetic analysis, it is proposed that strain YIM CF22T represents a novel species of the genus Actinoplanes, for which the name Actinoplanes deserti sp. nov. is proposed. The type strain is YIM CF22T (= KCTC 39543T = CCTCC AB2018113T). [ABSTRACT FROM AUTHOR]

To gain insights into the adaptive characteristics of ephemeral plants and enrich their potential for resource exploitation, the adaptive changes in two highly dominant species (Malcolmia scorpioides and Isatis violascens) to soil habitats (aeolian soil, AS; grey desert soil, GS) were investigated from the aspects of root morphology, physiology, and metabolism in this study. The results revealed that changes in root morphology and enzyme activity were affected by soil habitat. Total root length (TRL), root volume (RV) and root surface area (RSA) were higher in GS than in AS. The levels of proline (Pro), glutathione (GSH), soluble sugar (SS), and lysine (Lys) were higher in GS than in AS. Untargeted LC–MS metabolomics indicates that root metabolites of both species differed among the two soil habitats. Root responses to different soil habitats mainly affected some metabolic pathways. A total of 780 metabolites were identified, common differential metabolites (DMs) in both species included amino acids, fatty acids, organic acids, carbohydrates, benzene and derivatives, and flavonoids, which were mainly involved in carbohydrate metabolism, amino acid metabolism, flavonoid biosynthesis and fatty acid metabolism, and their abundance varied among different habitats and species. Some key DMs were significantly related to root morphology and enzyme activity, and indole, malonate, quercetin, uridine, tetrahydroharmine, and gluconolactone were important metabolites associated with root growth. Therefore, the response changes in root growth and metabolite of ephemeral plants in response to soil habitats reflect their ecological adaptation, and lay a foundation for the exploitation of plant resources in various habitats. [Display omitted] • Soil habitats affected ephemeral plants root morphology and enzyme activities. • Overall metabolic characteristics of ephemeral plant roots differed in the two habitats. • Both plant species share some of the same metabolic pathways for soil habitats. • Variation pattern in differential metabolites differed in the two soil habitats. • Some differential metabolites affected by soil habitat were related to root growth. [ABSTRACT FROM AUTHOR]

Microbial-induced calcite precipitation (MICP) is a soil amelioration technique aiming to mitigate different environmental and engineering concerns, including desertification, soil erosion, and soil liquefaction, among others. The hydrolysis of urea, catalyzed by the microbial enzyme urease, is considered the most efficient microbial pathway for MICP. Biostimulated MICP relies on the enhancement of indigenous urea-hydrolyzing bacteria by providing an appropriate enrichment and precipitation medium, as opposed to bioaugmentation, which requires introducing large volumes of exogenous bacterial cultures into the treated soil along with a growth and precipitation medium. Biostimulated MICP in desert soils is challenging as the total carbon content and the bacterial abundance are considerably low. In this study, we examined the biostimulation potential in soils from the Negev Desert, Israel, for the purpose of mitigation of topsoil erosion in arid environments. Incubating soil samples in urea and enrichment media demonstrated effective urea hydrolysis leading to pH increase, which is necessary for calcite precipitation. Biostimulation rates were found to increase with concentrations of energy (carbon) source in the stimulation media, reaching its maximal levels within 3 to 6 days. Following stimulation, calcium carbonate precipitation was induced by spiking stimulated bacteria in precipitation (CaCl2 enriched) media. The results of our research demonstrate that biostimulated MICP is feasible in the low-carbon, mineral soils of the northern Negev Desert in Israel.