Sunil Mundra

Introduction: Sustainable strategies have been implemented to enhance plant development and productivity, including intercropping systems. This approach is particularly effective in arid regions, where diverse microbial populations associated with intercropping plants contribute significantly to stress tolerance and plant growthpromoting. Methods: We evaluated how intercropping and monocropping systems influence the diversity, functional traits, and stress tolerance of root-associated bacteria. Root endophytic and rhizosphere bacteria were isolated from intercropping and monocropping systems under arid conditions and evaluated for plant growth-promoting traits, enzymatic activities, exopolysaccharide and cellulose production, biofilm formation under drought stress, and tolerance to drought, salinity, and heat stress. Results and discussion: Eighty bacterial isolates were characterized, most of which exhibited multiple plant growth-promoting traits and tolerance to environmental stress. Overall, Bacillus spp. were the dominant bacteria among endophyte and rhizosphere communities. In alfalfa-broad and Egyptian wheat-broad intercropping, Bacillus spp. were more common, whereas Pseudomonas spp. were more common in barley-mustard intercropping. Multivariate analysis of functional traits (NMDS) revealed that bacterial communities were primarily structured by niche (endophytic vs. rhizosphere) rather than by intercropping type. The results suggest that rhizosphere bacteria associated with intercropping enhanced nitrogen fixation compared to those from monocropping systems, and the exopolysaccharide produced by endophytic isolates from intercropping using glucose as a carbon source varied from monocropping. Based on our results, the intercropping system creates a favorable microenvironment for certain bacteria, such as Bacillus spp. and Pseudomonas spp., which possess specific plant growth-promoting traits suitable for harsh environments, such as arid regions. These findings support other studies showing that bacteria adapted to extreme conditions, and isolated from diverse and multiple cropping systems, can function as plant bioinoculants, supporting plant species under adverse conditions.

Atmospheric carbon dioxide (CO₂) sequestration is commonly attributed to plant-driven processes, while the contribution of soil microorganisms remains comparatively underexplored. This imbalance is particularly relevant in dryland ecosystems, which cover over 45 % of Earth’s land surface and store a substantial fraction of global soil organic carbon. Despite their vast extent and ecological significance, current frameworks often overlook the metabolic potential of microbial communities inhabiting these environments. In drylands, microorganisms have evolved diverse metabolic strategies to capture and store atmospheric carbon, supported by multiple carbon-fixation pathways that extend beyond the Calvin–Benson–Bassham cycle. Here, we examine microbial carbon fixation in dryland ecosystems as an underexplored component of the global carbon cycle. We highlight the diversity, metabolic flexibility, and stress adaptations of carbon-fixing microbes and discuss the dominant pathways supporting carbon assimilation under arid conditions. By integrating evidence across studies, the findings suggest that microbial processes in drylands can contribute to carbon sequestration in ways not fully captured by plant-centered perspectives. This review provides a framework for incorporating microbial metabolic diversity into current models of terrestrial carbon cycling and highlights its relevance for climate change mitigation strategies.

Atmospheric carbon dioxide (CO₂) sequestration is commonly attributed to plant-driven processes, while the contribution of soil microorganisms remains comparatively underexplored. This imbalance is particularly relevant in dryland ecosystems, which cover over 45 % of Earth’s land surface and store a substantial fraction of global soil organic carbon. Despite their vast extent and ecological significance, current frameworks often overlook the metabolic potential of microbial communities inhabiting these environments. In drylands, microorganisms have evolved diverse metabolic strategies to capture and store atmospheric carbon, supported by multiple carbon-fixation pathways that extend beyond the Calvin–Benson–Bassham cycle. Here, we examine microbial carbon fixation in dryland ecosystems as an underexplored component of the global carbon cycle. We highlight the diversity, metabolic flexibility, and stress adaptations of carbon-fixing microbes and discuss the dominant pathways supporting carbon assimilation under arid conditions. By integrating evidence across studies, the findings suggest that microbial processes in drylands can contribute to carbon sequestration in ways not fully captured by plant-centered perspectives. This review provides a framework for incorporating microbial metabolic diversity into current models of terrestrial carbon cycling and highlights its relevance for climate change mitigation strategies.

Atmospheric carbon dioxide (CO₂) sequestration is commonly attributed to plant-driven processes, while the contribution of soil microorganisms remains comparatively underexplored. This imbalance is particularly relevant in dryland ecosystems, which cover over 45 % of Earth’s land surface and store a substantial fraction of global soil organic carbon. Despite their vast extent and ecological significance, current frameworks often overlook the metabolic potential of microbial communities inhabiting these environments. In drylands, microorganisms have evolved diverse metabolic strategies to capture and store atmospheric carbon, supported by multiple carbon-fixation pathways that extend beyond the Calvin–Benson–Bassham cycle. Here, we examine microbial carbon fixation in dryland ecosystems as an underexplored component of the global carbon cycle. We highlight the diversity, metabolic flexibility, and stress adaptations of carbon-fixing microbes and discuss the dominant pathways supporting carbon assimilation under arid conditions. By integrating evidence across studies, the findings suggest that microbial processes in drylands can contribute to carbon sequestration in ways not fully captured by plant-centered perspectives. This review provides a framework for incorporating microbial metabolic diversity into current models of terrestrial carbon cycling and highlights its relevance for climate change mitigation strategies.

Soil eukaryotes, including fungi, protists, plants, and animals, are central to biosphere functioning and resilience. The Global Standardised Soil Eukaryome Dataset (GloSED) is the first dataset encompassing the entire spectrum of soil eukaryotes, covering 4,063 sampling sites in 121 countries on all continents, revealing nearly one million operational taxonomic units. All samples were collected and analysed using a standardised protocol minimizing technical biases. Long-read sequencing of full-length ITS and 18S-V9 regions provide broad taxonomic coverage and high-resolution identification supported by specialist curation of “dark taxa”. A rigorous bioinformatic processing ensures against homopolymer errors, PCR-mediated chimeras, and index switching providing high data quality. The dataset is supported by raw sequences and an open-source containerised workflow for reproducible analyses. The samples are accompanied by land-cover description and directly measured soil pH, δ ¹³ C, δ ¹⁵ N, as well as P, K, Ca, Mg, and total C and N contents. GloSED is the first database that enables ecological and biogeographic studies of entire soil eukaryotic communities from local to global scales.

Biological soil crusts (biocrusts) regulate eco-hydrological processes in arid landscapes; however, their spatiotemporal coupling with soil salinity and climate remains poorly quantified in hyper-arid environments of the Arabian Peninsula. Here, we integrated multi-year satellite observations to map soil salinity and biocrust distribution across the United Arab Emirates (UAE) from 2018 to 2023. Landsat-8 imagery was used to derive the Normalized Difference Salinity Index (NDSI) and Biological Soil Crust Index (BSCI), and supervised machine-learning classification was applied to monitor soil salinity and biocrust occurrence, achieving overall accuracies of ~80% and ~81%, respectively. The results revealed pronounced spatiotemporal variability in soil salinity and biocrust coverage, particularly in coastal sabkhas, agricultural lands, and urban areas. The annual extent of soil salinity was positively correlated with temperature (R² = 0.828; p-value <0.05), while its relationship with precipitation remained relatively weak under the hyper-arid climatic conditions of the UAE. Annual distribution of biocrusts within the study area was more strongly influenced by temperature than precipitation variability. An inverse relationship between soil salinity and biocrust coverage indicated that elevated salinity limits crust formation (R² = 0.94, p<0.01). Greater variability in both soil salinity and biocrusts in croplands and coastal zones reflects anthropogenic disturbances associated with irrigation and land-use change. Relationships between biocrusts, soil moisture, and heterotrophic respiration derived from the Soil Moisture Active Passive (SMAP) products further highlight complex interactions between crust development, soil moisture availability, and carbon fluxes. This study demonstrates the potential of satellite remote sensing for long-term monitoring of coupled soil salinity and biocrust dynamics in hyper-arid ecosystems, and highlights the sensitivity of biocrusts to environmental stressors such as climatic warming and salinization. These findings emphasize the role of remote sensing in supporting soil salinity management and enabling targeted biocrust conservation strategies to enhance ecosystem resilience in hyper-arid environments.

Aims: Fungal communities in boreal forest soils are highly diverse, both taxonomically and functionally, with the majority of fungi associated with living or dead plants as saprotrophs, pathogens or mycorrhizal symbionts. The aim of this study was to examine to what extent soil fungal communities are structured by the above-ground vegetation versus topographic and edaphic factors. Methods: We take advantage of a vegetation survey in which plant communities have been monitored in plots located along topographic and edaphic gradients in a boreal forest area in southern Norway, spanning from mesic spruce forests to xeric pine forests. To survey the corresponding fungal communities, we applied DNA metabarcoding of soil samples collected from the same permanent plots. Results: The fungal soil communities exhibited a strong structure along the same edaphic and topographic gradients as the vegetation. Plant community composition explained most of the variation in fungal community composition followed by edaphic factors and topography. The xeric pine forest was characterized by high CN ratios, ericoid vegetation, and a correspondingly higher abundance of Ascomycota, many of which form ericoid mycorrhizae or are root-associated. The submesic spruce forest was characterized by higher pH, lower CN ratios, diverse understory vegetation and high abundance of ectomycorrhizal and white-rot litter decomposer Basidiomycota. Conclusions: The gradient from mesic spruce- to xeric pine-dominated forest is ubiquitous in boreal forests, and we here show a strong link between composition of vegetation and fungal communities, highlighting long-term effects influencing both plant and fungal communities in similar and predictable ways.

Mangroves in arid environments represent unique ecological niches that support a diverse range of microorganisms. Endophytic bacteria residing within host plants play a crucial role in promoting plant growth by enhancing pathogen resistance and alleviating environmental stress. Identifying novel stress‐tolerant strains, specific to arid environments, is essential for expanding the repertoire of plant growth‐promoting bacteria (PGPB). In this study, we investigated the saline tolerance of the endophytic bacterium strain E1, previously isolated from the root of Avicenna marina (grey mangrove). Whole‐genome sequence (WGS), phylogenetics and average nucleotide identity (ANI) analysis were performed. The strain exhibited high salinity tolerance, growing in conditions up to 11% NaCl, and was phylogenetically closely related to Bacillus cereus . Genome analysis revealed multiple PGP‐related genes, including those involved in nitrogen fixation, phosphate and potassium solubilization, and iron siderophore transport. Additionally, genes associated with detoxification, hormone biosynthesis (Including Indole‐3‐Acetic acid and cytokinin), salt and heat stress tolerance, as well as volatile compound production, were identified. A greenhouse assay with tomato plants was conducted to assess the ability of strain E1 to alleviate saline stress (50, 100, and 150 mM NaCl) and its impact on spectral indices, antioxidant enzymes, and electrolyte leakage (EL). Inoculation with strain E1 significantly enhanced all measured growth parameters, including shoot and root length and weight (both fresh and dry) as well as leaf area. These improvements were reflected in elevated spectral indices, increased antioxidant enzymes, improved cell stability, and reduced EL compared to control and NaCl‐treated plants. These findings highlight Bacillus cereus strain E1 as a promising, stress‐tolerant endophyte for arid agriculture, capable of promoting tomato growth through multiple mechanisms under challenging environmental conditions.

Background/Objectives: Antibiotic resistance is a growing global health threat, requiring comprehensive investigations into the occurrence, distribution, and diversity of antibiotics across environmental systems. This study aimed to examine the distribution and prevalence of commonly used antibiotics in various wastewater sources across the United Arab Emirates (UAE), providing insights into potential environmental reservoirs contributing to antimicrobial resistance dissemination. Methods: Wastewater samples were collected from the outlets of three hospitals, three residential communities, and the influent and return activated sludge of two wastewater treatment plants. Samples were prepared using solid-phase extraction (SPE) and analyzed via liquid chromatography–mass spectrometry (LC–MS/MS) to quantify antibiotic concentrations and compare their distribution among sources. Results: Significant variations were observed in antibiotic concentrations across the different wastewater sources. Ciprofloxacin concentrations were highest in hospital wastewater, reaching up to 247.9 ng/mL, while cefuroxime and vancomycin ranged between 0.2 and 10.9 ng/mL across samples. Clindamycin was notably prevalent in wastewater treatment plant samples (up to 10.9 ng/mL), whereas vancomycin and cefuroxime were dominant in residential community samples, reflecting diverse antibiotic usage patterns and persistence in treatment systems. Conclusions: The findings reveal substantial antibiotic contamination in United Arab Emirates wastewater systems, underscoring the need for ongoing surveillance and regulatory measures. Continuous monitoring, coupled with effective wastewater treatment and antibiotic stewardship strategies, is critical to mitigating the environmental spread of antimicrobial resistance and safeguarding public and environmental health.

Salt stress is a significant environmental constraint that hinders plant growth and poses a threat to global agriculture. This study investigates the potential of the halophilic bacterium Bacillus paranthracis (strain Endo10) to enhance salt stress tolerance in tomato plants. We assessed its effects as a plant growth-promoting rhizobacterium (PGPR) by measuring growth performance, photosynthetic efficiency, spectral reflectance, and antioxidant defense mechanisms under saline conditions. The result showed that the inoculation of tomato plants with B. paranthracis significantly mitigated NaCl stress, enhancing growth and physiological performance. Treated plants exhibited significantly greater overall growth, including increased biomass and root development, compared to the NaCl controls. Chlorophyll-a fluorescence and spectral reflectance analysis confirmed superior photosynthetic efficiency (PSII) in inoculated plants. They also demonstrated stronger antioxidant activity, with elevated SOD, POD, APX, and CAT enzyme levels and reduced electrolyte leakage. These findings demonstrate that B. paranthracis improves tomato plant health under saline stress by enhancing photosynthetic efficiency, stimulating antioxidant enzyme activity, and leveraging key growth-promoting traits. Consequently, B. paranthracis is a promising bioinoculant for sustainable agriculture in salt-affected soils.