Biology subjects

Gillor, O.

Publications and source records attributed to Gillor, O..

5 recordsLinked to original sources

bioRxiv2026

Dryland soil rewetting induces strong VOC emissions with potential to form ozone and aerosols

Biogenic volatile organic compounds (VOCs) significantly influence atmospheric chemistry, yet the importance of microbial VOC emissions remains understudied. We investigate petrichor VOC emissions, the characteristic scent following rainfall after prolonged drought, in an aridity gradient across Israel, by simulating soil rewetting events. Rewetting triggered strong VOC fluxes (1-3.5 nmol m-2 s-1 ground area) dominated by sesquiterpenes and benzenoids, with emission patterns linked to climatic regions, soil aridity, and microbial community composition. Petrichor consisted of a complex bouquet of 58 VOCs, and the initial VOC burst resembled the CO2 pulse of the Birch effect. Petrichor emissions showed ozone and secondary organic aerosol formation potentials comparable in magnitude to those estimated for anthropogenic VOC sources in Israel. Despite compositional differences, emissions were of similar magnitudes across the aridity gradient. Given that drylands cover nearly half of Earths terrestrial surface and are expanding, these episodic microbial VOC emissions may represent a significant, previously overlooked source of reactive carbon with potential implications for regional and global atmospheric chemistry.

microbiology↗

bioRxiv2025

Aridity drives global convergence of desert microbiomes and biogeochemical activities

Deserts cover a third of the worlds surface, supporting unique biomes and ecosystem services. Yet, we lack a comprehensive assessment of what defines and drives the microbial communities that dominate life in these regions. Here, we conducted a standardized field survey in contrasting cold, hot, and polar deserts across the seven continents, and observed geographically distant deserts share similar structure, function, and activities. Desert communities are dominated by genomically streamlined Actinobacteriota and Chloroflexota, and compared with non-desert soils, are significantly enriched with stress tolerance genes, mobile genetic elements, and antiviral strategies, revealing previously unknown ecological and evolutionary dynamics. Metabolically, these communities exhibit reduced capacity for carbohydrate and protein degradation, and instead are enriched for chemosynthetic carbon fixation, continuous energy harvesting using atmospheric trace gases and sunlight, and energy reserve biosynthesis. All sampled soils mediated respiration, trace gas oxidation, and carbon fixation, with detectable activity even in hyper-arid Atacama and Antarctic soils at the margins of life. Driver analyses identified aridity as the primary overriding driver of the microbial communities and biogeochemical activities. Collectively, these findings suggest that aridity selects for metabolically self-sufficient taxa capable of continuously meeting energy and carbon needs independently of vegetation-derived inputs, while enduring physicochemical stressors and potentially elevated viral pressure. These new insights are integral to forecast the future of soils amid increasing desertification. Significance statementDesert soils occupy a vast and expanding portion of Earth, yet what defines and governs their dominant microbial life remains incompletely defined. By assessing the composition, capabilities, and activities of microbial communities across deserts on all seven continents, we identify unifying signatures of life under extreme water limitation. We show microbial communities are highly self-sufficient, capable of acquiring energy and carbon even where plant inputs are minimal. This planetary-scale understanding of the desert microbiome has important ramifications for forecasting potential shifts of microbial communities and the services they provide as desertification intensifies.

microbiology↗

bioRxiv2023

Cobalamin production in phototrophic and mixotrophic cultures of nine duckweed species (Lemnaceae)

To feed the rapidly increasing world population, food production will have to double while the amount of water and arable land remain unchanged. Therefore, we must transition to environmentally sustainable, but just as nutritious diets by 2050. This will require drastic reduction in animal-based foods and increasing plant-based foods. Plant- based diets are more sustainable and healthier, with but one exception, plants are low in cobalamin (vitamin B12). Only a few plant and fungi species contain cobalamin, and some of the cobalamin forms present in algae and mushrooms are not available to humans. Recently, the smallest known plant, the edible duckweed Wolffia globosa Mankai, was shown to contain high concentrations of bioavailable cobalamin. We hypothesized that the production of bioavailable cobalamin is not unique to W. globosa Mankai but is common to other duckweed species. We also hypothesized that cobalamin production depends on the conditions under which the duckweed is grown. To test our hypotheses, we cultivated nine duckweed species under mixotrophic and phototrophic conditions, then measured the concentration and identified the bioavailability of cobalamin using biological and analytical methods. Our results showed that all duckweed species tested produce bioavailable cobalamin while pseudocobalamin (the non-available form of cobalamin) was not detected. We also found that mixotrophic conditions enhanced duckweed growth but reduced cobalamin concentrations. Our results establish duckweed species as a novel source of plant-derived bioavailable cobalamin and highlight the effect of growth conditions on production. More research is needed to identify the bacteria responsible for the production of cobalamin in duckweed and to optimize the conditions for cobalamin production.

plant biology↗

bioRxiv2021

The response of desert biocrust bacterial communities to hydration-desiccation cycles

Rain events in arid environments are highly unpredictable, interspersing extended periods of drought. Therefore, following changes in desert soil bacterial communities during hydration-desiccation cycles in the field, was seldom attempted. Here, we assessed rain-mediated dynamics of active community in the Negev Desert biological soil crust (biocrust), and evaluated the changes in bacterial composition, potential function, and photosynthetic activity. We predicted that increased biocrust moisture would resuscitate the phototrophs, while desiccation would inhibit their activity. Our results show that hydration increased chlorophyll content, resuscitated the biocrust Cyanobacteria, and induced potential phototrophic functions. However, decrease in the soil water content did not immediately decrease the phototrophs activity, though chlorophyll levels decreased. Moreover, while the Cyanobacteria relative abundance significantly increased, Actinobacteria, the former dominant taxa, significantly decreased in abundance. We propose that, following a rain event biocrust moisture significantly decreased, almost to drought levels, yet the response of the active bacterial community lagged, in contrast to topsoil. Possible explanations to the described rain-mediated bacteria dynamics are discussed.

microbiology↗

bioRxiv2020

The role of ecosystem engineers in shaping the diversity and function of arid soil bacterial communities

Ecosystem engineers (EEs) are present in every environment and are known to strongly influence ecological processes and thus shape the distribution of species and resources. In this study, we assessed the direct and indirect effect of two EEs (perennial shrubs and ant nests), individually and combined, on the composition and function of arid soil bacterial communities. To that end, top soil samples were collected in the Negev Desert Highlands during the dry season from four patch types: (1) barren soil; (2) under shrubs; (3) near ant nests; or (4) near ant nests situated under shrubs. The bacterial composition was evaluated in the soil samples (fourteen replicates per patch type) using 16S rRNA gene amplicon sequencing, together with physico-chemical measures of the soil, and the potential functions of the community. We have found that the EEs differently affected the community composition. Indeed, barren patches supported a soil microbiome, dominated by Rubrobacter and Proteobacteria, while in EE patches the Deinococcus-Thermus phylum was dominating. The presence of the EEs similarly enhanced the abundance of phototrophic, nitrogen cycle and stress- related genes. In addition, only when both EEs were combined, were the soil characteristics altered. Our results imply that arid landscapes foster unique communities selected by each EE(s), solo or in combination, yet these communities have similar potential biological traits to persist under the harsh arid conditions. Environments with multiple EEs are complicated to study due to the possibility of non-additive effects of EEs and thus further research should be done. IMPORTANCEEcosystem engineers are organisms that can create, modify, or maintain their habitat. They are present in various environments but are particularly conspicuous in desert ecosystems, where their presence is tightly linked to vital resources like water or nutrients. Despite their key role in structuring and controlling desert ecosystems, joint engineering, and their effect on soil function, are unknown. Our study explores the contributions of key ecosystem engineers to the diversity and function of their soil microbiome allowing better understanding of their role in shaping habitats and engineering their activity

microbiology↗