Deciphering the potential niche of novel black yeast fungal isolates in a biological soil crust based on genomes, phenotyping, and melanin regulation

Black yeasts are polyextremotolerant fungi that contain high amounts of melanin in their cell wall and maintain a primarily yeast form. These fungi grow in xeric, nutrient deplete environments which implies that they require highly flexible metabolisms and the ability to form lichen-like mutualisms with nearby algae and bacteria. However, the exact ecological niche and interactions between these fungi and their surrounding community is not well understood. We have isolated two novel black yeast fungi of the genus Exophiala: JF 03-3F “Goopy” E. viscosium and JF 03-4F “Slimy” E. limosus, which are from dryland biological soil crusts. A combination of whole genome sequencing and various phenotyping experiments have been performed on these isolates to determine their fundamental niches within the biological soil crust consortium. Our results reveal that these Exophiala spp. are capable of utilizing a wide variety of carbon and nitrogen sources potentially from symbiotic microbes, they can withstand many abiotic stresses, and can potentially provide UV resistance to the crust community in the form of secreted melanin. Besides the identification of two novel species within the genus Exophiala, our study also provides new insight into the production and regulation of melanin in extremotolerant fungi.

INFLUENCE OF VARIABLE SPEED INDICATORS OF THE ROTARY HARVEST BZR-9,0 WORK ON THE SUNFLOWER INTERROW TREATMENT PERFORMANCE QUALITY

The purpose of the research is to investigate the quality of inter-row tillage with a rotary harrow depending on the speed regimes in conditions of high soil hardness.Research methods: theoretical - analysis of information resources and research results of rotary harrows; experimental field - testing of the machine in the economic conditions of LLC "Nosivka Agro", village Ploske Nosiv district of Chernihiv region with the fixation of agronomic indicators; instrumental measurements and expert evaluation; statistical - mathematical processing of the obtained indicators.Results.Experimental field studies of the influence of the speed modes of the rotary harrow BZR-9.0 on the efficiency of inter-row cultivation have been carried out.The nomenclature of quality criteria and their achieved level have been established by expert evaluation.It has been analytically established that the rotary harrow mulches the topsoil well, destroys the soil crust, loosens the soil and destroys filamentous weeds, thus creating ideal conditions for the initial development of the plant root system and providing a strong start to their growth. Conclusions. Rotary harrows, widely available on the Ukrainian market, are increasingly in demand as an effective tool for weed control and soil crust destruction in order to improve aeration and water saturation of crops in conditions of increased soil dryness. Theoretical analysis of information sources confirms that needle harrows can be successfully used for continuous and inter-row cultivation of crops in small and medium-sized farms. The physical parameters obtained as a result of experimental researches testify that with change of speed from 9 km / h to 15 km / h the harrow tooth rotary BZR-9,0 in interrow spacing with a protective zone of 11 cm provides qualitative cultivation of soil with a sufficient level of agrotechnical indicators - degree of destruction. soil crust in the range of 91-98 %, and the percentage of damaged plants is at the level of excellent and satisfactory values. There are no undamaged areas of crust with an area of more than 5 cm2, which significantly impede water and air permeability.

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.

Martian subsurface cryosalt expansion and collapse as trigger for landslides

On Mars, seasonal martian flow features known as recurring slope lineae (RSL) are prevalent on sun-facing slopes and are associated with salts. On Earth, subsurface interactions of gypsum with chlorides and oxychlorine salts wreak havoc: instigating sinkholes, cave collapse, debris flows, and upheave. Here, we illustrate (i) the disruptive potential of sulfate-chloride reactions in laboratory soil crust experiments, (ii) the formation of thin films of mixed ice-liquid water “slush” at −40° to −20°C on salty Mars analog grains, (iii) how mixtures of sulfates and chlorine salts affect their solubilities in low-temperature environments, and (iv) how these salt brines could be contributing to RSL formation on Mars. Our results demonstrate that interactions of sulfates and chlorine salts in fine-grained soils on Mars could absorb water, expand, deliquesce, cause subsidence, form crusts, disrupt surfaces, and ultimately produce landslides after dust loading on these unstable surfaces.