Soil Yeast Research Articles

Temperature-dependent catabolic traits of cold-adapted soil yeasts Goffeauzyma gilvescens and Naganishia albidosimilis from Hornsund, Svalbard

Studies on the diversity and catabolic functionality of fungi in Arctic soils are still scarce. This knowledge gap needs to be urgently addressed, as global warming may have unpredictable effects on cold-adapted fungal species. We isolated two yeast species of the family Filobasidiaceae: Goffeauzyma gilvescens and Naganishia albidosimilis, from soil in central Spitsbergen (Svalbard) and characterised their metabolic properties at two temperatures, 4°C and 20°C, in a laboratory test using Biolog® FF plates. The results of the Biolog® test, which followed the molecular identification of the strains, confirmed that the two species differed in their functional (catabolic) characteristics. The effect of temperature was also highly significant and the metabolic characteristics of two species varied between the two temperatures tested. As expected, among other chemical guilds of substrates on Biolog® plates, carbohydrates were the most used and also the most segregating of the strains studied, especially at 20°C. However, the relative use of almost all substrate groups changed between the two temperatures for both species tested, indicating that temperature can also affect soil microorganisms indirectly by altering their metabolic pathways. As soil microorganisms form a complex trophic and non-trophic network, such changes in metabolism under increasing temperature may also alter relationships between species and between species and the environment. Our study contributes to a better understanding of the microbial ecology of the unique ecosystem of polar soils.

Seasonal Dynamics of Culturable Yeasts in Ornithogenically Influenced Soils in a Temperate Forest and Evaluation of Extracellular Enzyme Secretion in Tausonia pullulans at Different Temperatures.

The culturable yeast communities in temperate forest soils under the ornithogenic influence were studied in a seasonal dynamic. To investigate the intense ornithogenic influence, conventional and "live" feeders were used, which were attached to trees in the forest and constantly replenished throughout the year. It was found that the yeast abundance in the soil under strong ornithogenic influence reached the highest values in winter compared to the other seasons and amounted to 4.8 lg (cfu/g). This was almost an order of magnitude higher than the minimum value of yeast abundance in ornithogenic soils determined for summer. A total of 44 yeast species, 21 ascomycetes and 23 basidiomycetes, were detected in ornithogenic soil samples during the year. These included soil-related species (Barnettozyma californica, Cyberlindnera misumaiensis, Cutaneotrichosporon moniliiforme, Goffeauzyma gastrica, Holtermanniella festucosa, Leucosporidium creatinivorum, L. yakuticum, Naganishia adeliensis, N. albidosimilis, N. globosa, Tausonia pullulans, and Vanrija albida), eurybionts (yeast-like fungus Aureobasidium pullulans, Debaryomyces hansenii, and Rhodotorula mucilaginosa), inhabitants of plant substrates and litter (Cystofilobasidium capitatum, Cys. infirmominiatum, Cys. macerans, Filobasidium magnum, Hanseniaspora uvarum, Metschnikowia pulcherrima, and Rh. babjevae) as well as a group of pathogenic and opportunistic yeast species (Arxiozyma bovina, Candida albicans, C. parapsilosis, C. tropicalis, Clavispora lusitaniae, and Nakaseomyces glabratus). Under an ornithogenic influence, the diversity of soil yeasts was higher compared to the control, confirming the uneven distribution of yeasts in temperate forest soils and their dependence on natural hosts and vectors. Interestingly, the absolute dominant species in ornithogenic soils in winter (when the topsoil temperature was below zero) was the basidiomycetous psychrotolerant yeast T. pullulans. It is regularly observed in various soils in different geographical regions. Screening of the hydrolytic activity of 50 strains of this species at different temperatures (2, 4, 10, 15 and 20 °C) showed that the activity of esterases, lipases and proteases was significantly higher at the cultivation temperature. Ornithogenic soils could be a source for the relatively easy isolation of a large number of strains of the psychrotolerant yeast T. pullulans to test, study and optimize their potential for the production of cold-adapted enzymes for industry.

Impact of Sodium Alginate-Encapsulated Iron Nanoparticles and Soil Yeasts on the Photosynthesis Performance of Lactuca sativa L. Plants.

In a scenario of accelerated global climate change, the continuous growth of the world population, and the excessive use of chemical fertiliser, the search for sustainable alternatives for agricultural production is crucial. The present study was conducted to evaluate the plant growth-promoting (PGP) characteristics of two yeast strains, Candida guilliermondii and Rhodotorula mucilaginosa, and the physicochemical characteristics of nanometric capsules and iron oxide nanoparticles (Fe2O3-NPs) for the formulation of nanobiofertilisers. The physiological and productive effects were evaluated in a greenhouse assay using lettuce plants. The results showed that C. guilliermondii exhibited higher tricalcium phosphate solubilisation capacity, and R. mucilaginosa had a greater indole-3-acetic acid (IAA) content. The encapsulation of C. guilliermondii in sodium alginate capsules significantly improved the growth, stomatal conductance, and photosynthetic rate of the lettuce plants. Physicochemical characterisation of the Fe2O3-NPs revealed a particle size of 304.1 nm and a negative Z-potential, which indicated their stability and suitability for agricultural applications. The incorporation of Fe2O3-NPs into the capsules was confirmed by SEM-EDX analysis, which showed the presence of Fe as the main element. In summary, this study highlights the potential of nanobiofertilisers containing yeast strains encapsulated in sodium alginate with Fe2O3-NPs to improve plant growth and photosynthetic efficiency as a path toward more sustainable agriculture.

The Biosynthesis, Accumulation of Phenolic Compounds and Antioxidant Response in Lactuca sativa L. Plants Inoculated with a Biofertilizer Based on Soil Yeast and Iron Nanoparticles

Lettuce is a vegetable that contributes vitamins, minerals, fibre, phenolic compounds and antioxidants to the human diet. In the search for improving production conditions and crop health, the use of microorganisms with plant growth-promoting capabilities, such as soil yeasts (PGPY), in conjunction with nanotechnology could offer sustainable development of agroecosystems. This study evaluated the synthesis of health-promoting bioactive compounds in lettuce under the application of soil yeast and an iron nanoparticle (NP-Fe2O3) encapsulated in alginate beads. Two yeast strains, Candida guillermondii and Rhodotorula mucilaginosa, and a consortium of both yeasts were used in the presence and absence of Fe2O3-NPs. Phenolic compounds were identified and quantified via HPLC-ESI-Q-ToF and antioxidant activity. Ten phenolic compounds were identified, highlighting the chicoric acid isomer and two quercetin glycosides with high concentrations of up to 100 µg g−1 in treatments with C. guillermondii. Treatments with R. mucilaginosa and NPs-Fe2O3 presented an increase in antioxidant activity, mainly in TEAC, CUPRAC and DPPH activities in leaves, with significant differences between treatments. Therefore, the use of encapsulated soil yeasts is a viable alternative for application in vegetables to improve the biosynthesis and accumulation of phenolic compounds in lettuce and other crops.

Soil yeast diversity and their plant growth promoting activities in some forest soils of Assam, North-East India

Soil yeast diversity and their plant growth promoting activities in some forest soils of Assam, North-East India

Effect of yeast and mycorrhizae inoculation on tomato production under normal and water stress conditions

The integration of beneficial microorganisms into agricultural systems can improve crop resistance to stress and increase yields. We studied tomato (Solanum lycopersicum) production in a greenhouse experimental trial over a complete growing season. The experimental design involved three factors: irrigation condition (normal/low), addition of the arbuscular mycorrhizal fungi Funneliformis mosseae (with/without), and inoculation with four native soil yeasts (Candida aff. ralunensis; Candida sake; Lachancea nothofagi and Candida oleophila). Co-inoculation of F. mosseae and yeasts did not affect the tomato plants. Addition of F. mosseae increased mycorrhizal colonization and production variables regardless of irrigation level; however, its effects on growth were variable. None of the inoculated yeasts increased mycorrhizal colonization. C. aff. ralunensis and C. oleophila inoculation increased stem diameter under all conditions studied. C. aff. ralunensis inoculation enhanced fruit set and the fruit/flower ratio under normal irrigation conditions, while C. sake inoculation increased the fruit/flower ratio under low irrigation conditions. Arbuscular mycorrhizae inoculation is presented as a beneficial production strategy to increase plant tolerance and improve water use. We propose that C. aff. ralunensis and C. oleophila inoculation improves plant vigor. Highlights: Tomato production under greenhouse conditions was studied during a complete growing season following a three-factor trial: irrigation condition (normal/low), addition of arbuscular mycorrhizal fungi and inoculation with four native soil yeasts. Addition of arbuscular mycorrhizal increased mycorrhizal colonization and production variables regardless of irrigation level. Inoculation with two of the yeasts studied increased stem diameter under all conditions studied. Utilizing indigenous microorganisms could represent a promising alternative to external inoculants, potentially cutting down production costs and eliminating the necessity of introducing foreign microorganisms into the environment.

Antarctic Soil Yeasts with Fermentative Capacity and Potential for the Wine Industry.

Low fermentation temperatures are usually employed to obtain high-quality wines. This is especially interesting for white wine production since it prevents the loss of volatile compounds and a browning appearance; however, available fermentative yeasts do not usually tolerate low temperatures. Therefore, an interesting place to find new yeasts with cryotolerance is the Antarctic continent. From soil samples collected in Antarctica, 125 yeasts were isolated, of which 25 exhibited fermentative activity at 10 °C. After a fingerprinting assay, we classified the candidates into nine isotypes and sequenced internal transcribed spacer regions for their identification. These yeasts were identified as part of the Mrakia genus. Sugar and alcohol tolerance tests showed that some of these Antarctic soil yeasts were able to grow up to 9% alcohol, and 25% sugar was reached; however, they exhibited longer latency periods compared to the control Saccharomyces cerevisiae. The optimal growing temperature for the isolated Antarctic yeasts was between 10 °C and 15 °C. A comprehensive analysis of the results obtained showed that the isolates 10M3-1, 4M3-6, and 4B1-35 could be good candidates for fermentation purposes due to their alcohol, sugar tolerance, and growth features. Our results prove that it is possible to isolate fermentative yeasts from Antarctic soil with promising characteristics for their potential use in the wine production industry.

Assessment of soil yeasts Papiliotrema laurentii S-08 and Saitozyma podzolica S-77 for plant growth promotion and biocontrol of Fusarium wilt of brinjal.

This study aimed to determine the efficacy of the soil yeasts Papiliotrema laurentii S-08 and Saitozyma podzolica S-77 for plant growth promotion (PGP) and biocontrol of wilt disease in brinjal plants while applying yeasts individually or as a consortium in pot experiments. The yeasts were tested for various PGP characteristics and antagonistic activity against the phytopathogen Fusarium oxysporum f. sp. melongenae. Both the yeast isolates demonstrated some PGP attributes as well as inhibited the growth of the phytopathogen. A gas chromatography-mass spectrometry analysis of the yeast metabolites revealed the presence of several antifungal compounds. The pot experiment performed under nursery conditions showed that applying these yeasts, individually or in consortium, decreased the percent disease incidence in brinjal seedlings while significantly enhancing their growth parameters. Papiliotrema laurentii S-08 and S. podzolica S-77 can be used in brinjal plants as plant growth promoters and also as biocontrol agents against the brinjal wilt disease.

Wild and partially synanthropic bird yeast diversity, in vitro virulence, and antifungal susceptibility of Candida parapsilosis and Candida tropicalis strains isolated from feces.

Yeast complexes in the fecal samples of wild (Dendrocopos major, Picus viridis) and partially synanthropic (Bombycilla garrulus, Garrulus glandarius, Pica pica, and Pyrrhula pyrrhula) birds were studied in a forest ecosystem during winter. A total of 18 yeast species were identified: 16 ascomycetes and two basidiomycetes belonging to five subphyla of fungi: Saccharomycotina (15), Pezizomycotina (1), Agaricomycotina (1), and Pucciniomycotina (1). Most yeast species were found in the fecal samples of P. pyrrhula (Candida parapsilosis, C. zeylanoides, Debaryomyces hansenii, Hanseniaspora uvarum, Metschnikowia pulcherrima, Meyerozyma carpophila, M. guilliermondii, Rhodotorula mucilaginosa); the lowest number of yeast species was observed in the feces of B. garrulus (C. parapsilosis, C. zeylanoides, Met. pulcherrima, and Rh. mucilaginosa). The opportunistic species of the genus Candida were found only in feces of partially synanthropic birds: C. parapsilosis was observed in the feces of B. garrulus, G. glandarius, P. pica, and P. pyrrhula; its relative abundance was 69.3%, 49.1%, 10.5%, and 1.1%, respectively; C. tropicalis was observed in the feces of P. pica and G. glandarius; its relative abundance was 54.6% and 7.1%, respectively. Strains of C. parapsilosis and C. tropicalis isolated from the feces of partially synanthropic birds were evaluated for their susceptibility to conventional antifungal agents (fluconazole, voriconazole, amphotericin B) and hydrolytic activity. A total of 160 strains were studied. Resistance to fluconazole was detected in 86.8% of C. parapsilosis strains and in 87% of C. tropicalis strains; resistance to voriconazole was detected in 71.7% of C. parapsilosis and in 66.7% of C. tropicalis strains, and the lowest percentage of resistant strains was detected to amphotericin B, 2.8% and 3.7% in C. parapsilosis and C. tropicalis strains, respectively. Multiresistance was detected in one strain of C. parapsilosis isolated from P. pica feces and in one strain of C. tropicalis isolated from G. glandarius feces. Phospholipase and hemolysin activities in the strains of C. parapsilosis were low (mean Pz values of 0.93 and 0.91, respectively); protease activity was moderate (mean Pz value of 0.53). The ability to produce hydrolytic enzymes was higher in the isolated strains of C. tropicalis. The mean Pz values of phospholipase and hemolysin activities were moderate (mean Pz values of 0.63 and 0.60, respectively), whereas protease activity was high (mean Pz value of 0.32). Thus, wild and partially synanthropic birds play an important role in disseminating of various yeast species. These yeasts can enter the topsoil via feces and contribute to the formation of allochthonous and uneven soil yeast diversity in natural ecosystems. In addition, partially synanthropic birds can be vectors of virulent strains of opportunistic Candida species from urban environments to natural biotopes.

Effects of temporal and spatial scales on soil yeast communities in the peach orchard.

Shihezi Reclamation Area is located at the southern edge of the Junggar Basin, with natural, soil, and climatic conditions unique to the production of peaches. In turn, peach orchards have accumulated rich microbial resources. As an important taxon of soil fungi, the diversity and community structure changes of yeast in the soil of peach orchards on spatial and temporal scales are still unknown. Here, we aimed to investigate the changes in yeast diversity and community structure in non-rhizosphere and rhizosphere soils of peach trees of different ages in the peach orchard and the factors affecting them, as well as the changes in the yeast co-occurrence network in the peach orchard at spatial and temporal scales. High-through put sequencing results showed that a total of 114 yeast genera were detected in all soil samples, belonging to Ascomycota (60 genera) and Basidiomycota (54 genera). The most dominant genus, Cryptococcus, was present in greater than 10% abundance in each sample. Overall, the differences in yeast diversity between non-rhizosphere and rhizosphere soil of peach trees at 3, 8 and 15 years were not significant. Principal coordinate analysis (PCoA) showed that differences in yeast community structure were more pronounced at the temporal scale compared to the spatial scale. The results of soil physical and chemical analysis showed that the 15-year-old peach rhizosphere soil had the lowest pH, while the OM, TN, and TP contents increased significantly. Redundancy analysis showed that soil pH and CO were key factors contributing to changes in soil yeast community structure in the peach orchard at both spatial and temporal scales. The results of co-occurrence network analysis showed that the peach orchard soil yeast network showed synergistic effects as a whole, and the degree of interactions and connection tightness of the 15-year-old peach orchard soil yeast network were significantly higher than the 3- and 8-year-old ones on the time scale. The results reveal the distribution pattern and mechanism of action of yeast communities in peach orchard soils, which can help to develop effective soil management strategies and improve the stability of soil microecology, thus promoting crop growth.

Yeasts Have Evolved Divergent Enzyme Strategies To Deconstruct and Metabolize Xylan.

Together with bacteria and filamentous fungi, yeasts actively take part in the global carbon cycle. Over 100 yeast species have been shown to grow on the major plant polysaccharide xylan, which requires an arsenal of carbohydrate active enzymes. However, which enzymatic strategies yeasts use to deconstruct xylan and what specific biological roles they play in its conversion remain unclear. In fact, genome analyses reveal that many xylan-metabolizing yeasts lack expected xylanolytic enzymes. Guided by bioinformatics, we have here selected three xylan-metabolizing ascomycetous yeasts for in-depth characterization of growth behavior and xylanolytic enzymes. The savanna soil yeast Blastobotrys mokoenaii displays superior growth on xylan thanks to an efficient secreted glycoside hydrolase family 11 (GH11) xylanase; solving its crystal structure revealed a high similarity to xylanases from filamentous fungi. The termite gut-associated Scheffersomyces lignosus, in contrast grows more slowly, and its xylanase activity was found to be mainly cell surface-associated. The wood-isolated Wickerhamomyces canadensis, surprisingly, could not utilize xylan as the sole carbon source without the addition of xylooligosaccharides or exogenous xylanases or even co-culturing with B. mokoenaii, suggesting that W. canadensis relies on initial xylan hydrolysis by neighboring cells. Furthermore, our characterization of a novel W. canadensis GH5 subfamily 49 (GH5_49) xylanase represents the first demonstrated activity in this subfamily. Our collective results provide new information on the variable xylanolytic systems evolved by yeasts and their potential roles in natural carbohydrate conversion. IMPORTANCE Microbes that take part in the degradation of the polysaccharide xylan, the major hemicellulose component in plant biomass, are equipped with specialized enzyme machineries to hydrolyze the polymer into monosaccharides for further metabolism. However, despite being found in virtually every habitat, little is known of how yeasts break down and metabolize xylan and what biological role they may play in its turnover in nature. Here, we have explored the enzymatic xylan deconstruction strategies of three underexplored yeasts from diverse environments, Blastobotrys mokoenaii from soil, Scheffersomyces lignosus from insect guts, and Wickerhamomyces canadensis from trees, and we show that each species has a distinct behavior regarding xylan conversion. These findings may be of high relevance for future design and development of microbial cell factories and biorefineries utilizing renewable plant biomass.

Screening for indole-3-acetic acid synthesis and 1-aminocyclopropane-carboxylate deaminase activity in soil yeasts from Chile uncovers Solicoccozyma aeria as an effective plant growth promoter

Abstract Background and aims Plant growth-promoting microorganisms (PGPMs) stimulate plant growth by a series of mechanisms, including atmospheric nitrogen fixation, phosphorus solubilization and the synthesis of plant hormones. Within the group of PGPMs, several species of bacteria and fungi have been extensively studied. However, little information is available with regard to soil yeasts. The present study was conducted to identify yeast strains isolated from different soils in Chile that present plant growth promotion activity. Methods Twenty-three strains were evaluated either for their capacity to synthesize indole-3-acetic acid or show aminocyclopropane-1-carboxylate deaminase activity. The effect on tomato seedling growth was evaluated in vitro, and two strains were selected for in vivo evaluation of plant growth and root ethylene synthesis. Results All the strains analyzed presented IAA synthesis within the range between 0.8 and 3.3 μg IAA mL−1. Solicoccozyma aeria (YCPUC75 and YCPUC79 strains) was the only yeast with ACC deaminase activity. In vitro inoculation of tomato seeds with eight of the evaluated strains resulted in an increase in the root volume and the number of lateral roots. In the second experiment, a 40% reduction in root ethylene synthesis was achieved by adding S. aeria (YCPUC79) to the root zone, which resulted in a 26% increase in plant growth. Conclusions Solicoccozyma aeria YCPUC79 is an effective plant growth promoter stimulating root growth and reducing root ethylene synthesis.

Sugarcane molasses as substrate to soil yeasts: Indole-3-acetic acid production and maize initial growth promotion

Plant growth promoter microorganisms (PGPM) associate with plants with benefits to plant productivity and protection. Among these microorganisms, yeasts have shown potential results. The aims here were to prospect yeasts with PGPM traits from organic maize soil and to evaluate molasses as substrate to produce indole-3-acetic acid (IAA). The isolates were selected considering IAA production, phosphate solubilization and phytopathogen control, following the phenotypic characterization. Seven strains were selected, identified by sequencing of D1/D2 domain of rDNA 26S gene and evaluated to produce IAA in molasses and potato dextrose broth (PD) with and without tryptophan. Non-filtered medium (NFM) and cell-free filtrate (CFF) of yeasts were used in an in vivo assay of maize seed germination and initial development. Twenty-eight yeasts were isolated, and 82% tested positive for the PGPM traits. The strains were identified as Torulaspora globosa (three strains), Aureobasidium pullulans, Candida pseudointermedia, Trichosporon asahii and Cryptococcus sp. T. globosa and C. pseudointermedia stood out regarding the IAA production. Molasses was more beneficial to cell growth and/or IAA production to five out of seven yeast strains. In general, the in vivo assay with maize demonstrated that the seed treatment with cell-free filtrates of yeasts promoted the initial development of plants (radicle and coleoptile), and the seed treatment with non-filtered medium resulted in higher maize plant development after 12 days of pot cultivation. The results indicate molasses as a medium for a prospective yeast-based biostimulant product for agricultural use and pointed out for the soil yeast species T. globosa and T. asahii as biological agents to contribute to plant growth promotion.

North-to-South diversity of lipomycetaceous yeasts in soils evaluated with a cultivation-based approach from 11 locations in Japan.

To understand the species distribution, diversity, and density of lipomycetaceous yeasts in soil based on their north-to-south location in Japan, 1146 strains were isolated from soil samples at 11 locations from Hokkaido to Okinawa Prefecture and taxonomically characterized. Lipomycetaceous yeast strains were isolated efficiently from soil by selecting watery mucoid-like colonies on agar plates with nitrogen-depleted medium. Twenty-four (80%) of the 30 known species of the genus Lipomyces were isolated from the soil samples collected in Japan, including species recently proposed. Among the species isolated, L. starkeyi was the most predominant in Japan, except on Iriomote Island, Okinawa, and accounted for 60-98% of the isolated strains. Lipomyces yarrowii was the dominant species on Iriomote Island (64%). The second most dominant species were L. chichibuensis in Saitama Prefecture and L. doorenjongii from Yamaguchi to Okinawa Prefecture. The species diversity of lipomycetaceous yeasts was in Japan and the significant correlation with the latitude of the sampling sites was revealed.

Volatiles of antagonistic soil yeasts inhibit growth and aflatoxin production of Aspergillus flavus

Minimizing Aspergillus flavus growth is an effective strategy to mitigate aflatoxin contamination in food and agricultural products. In the present investigation, we attempted to utilize soil-associated yeasts from the Western and Eastern Ghats of India against A. flavus to reduce aflatoxin contamination. Forty-five yeast isolates were screened against A. flavus using overlay and dual plate assays. Among them, 12 isolates effectively inhibited the growth of A. flavus. The 18S rDNA gene sequence analysis identified the twelve antagonistic isolates as belonging to Saccharomyces cerevisiae, Suhomyces xylopsoci, Pichia kudriavzevii, and Candida tropicalis. From the isolated yeasts, S. cerevisiae strains were selected for further evaluation based on the potential antagonistic activity. Volatiles of S. cerevisiae effectively suppressed the mycelial growth of A. flavus (P < 0.05) up to 92.1 % at 7 DAI. Scanning electron microscopic images of the fungus exposed to volatiles showed hyphal deformity and mycelial damage. Aflatoxin B1 (AFB1) production was drastically reduced up to 99.0 % in the volatile-exposed fungus compared to the control. The yeast strain YKK1 showed consistent Aspergillus flavus growth inhibition (80.7 %) and AFB1 production (98.1 %) for 14 days. Gas chromatography-mass spectrophotometry analysis of the yeast volatiles revealed the presence of antimicrobial compounds, including 1-pentanol, 1-propanol, ethyl hexanol, ethanol, 2-methyl-1-butanol, ethyl acetate, dimethyl trisulfide, p-xylene, styrene, and 1,4-pentadiene. The evaluated compounds of yeast volatiles, including ethyl acetate, hexanal, 1-propanol, 1-heptanol, 1-butanol, and benzothiazole, inhibited the fungal growth and AFB1 production of Aspergillus flavus when applied as pure chemicals. Benzothiazole at 5 mM was responsible for a high level of growth inhibition (23.6 %) and reduction of AFB1 synthesis (93.5 %). Hence, volatile compounds produced by soil yeast strains could be a potential biocontrol mechanism against aflatoxin contamination.

Effect of Some Ecological Factors on Occurrence of Yeasts in Soil and Sediment from Iraq

Soil is one of the favorable habitat for microorganism. It considered being the home of wide range of them in particularly, bacteria and fungi. Southern Iraq is characterized by a multiplicity of ecosystem, which include desert, agricultural and marine areas, each of which has special composition that differs from the neighboring system, whether in terms of vegetation or various environmental factors. This in diversity, in turn, may lead to microbial diversity that can be used in different biotechnologies. Regarding that little is known about yeast diversity in such habitats, and therefore the current study aims to assess the yeast community in soil and sediments samples from Basrah and Dhi-Qar provinces, Southern Iraq. Thirty-one species belong to 19 genera were encountered. The isolated species consist of 16 species of Ascomycota and 15 species of Basidiomycota. The soil of Basrah and Dhi-Qar support the growth of diverse species belonged to the genera Aureobasidium, Cutaneotrichosporon, Debaryomyces, Filobasidium Geotrichum, Hanseniaspora, Lodderomyces, Meyerozyma, Symmetrospora, Torulaspora, Vishniacozyma, Pichia, Yarrowia, Cystobasidium, Galactomyces, Rhodotorula, Wickerhamomyces, Candida and Naganishia. One hundred and twelve fungal isolates were identified using the conventional methods depending on morphological characteristics. CHROMagar candida was used as differential culture medium. Iodine stain was used to differentiate ascospores and basidiospores. In addition biochemical method represented by VITEK was used as well as molecular identification. This study represents the first report of occurrence of yeast species in soil and surface sediment samples from Basrah and Dhi-Qar provinces, Southern, Iraq, with effect of some ecological factors on isolation yeast from different location.

Changes in urban soil yeast communities after a reduction in household waste during the COVID-19 pandemic

The soils of streets, urban parks and suburban areas were examined for yeasts in the summer of 2020 on the territory of the southern cities of Russia and the Republic of Crimea: Krasnodar, Maykop, Sochi and Simferopol. The results of this study are compared with the results of a previous study carried out in these cities in 2019. This study was conducted three months after the lockdown due to the COVID-19 pandemic, which led to a sustained decline in household waste deposition in these areas. The number of tourists visiting these southern cities decreased significantly, and the number of walkers and visitors to urban parks fell sharply. In 2020, after the decline of household waste loads, the yeast abundance was slightly but reliably higher than in 2019. A total of 30 yeast species were observed - 11 ascomycetes and 19 basidiomycetes. This was more than in 2019 and was caused by twice as many autochthonous basidiomycetous yeast species (natural core community), which were found in urban soils only after the reduction in household waste in the environment - Apiotrichum dulcitum, A. laibachii, Saitozyma podzolica Solicoccozyma terricola. And at the same time, the proportion of clinically significant (opportunistic) yeasts, Candida sake and Meyerozyma guilliermondii, was much lower in 2020 than in 2019. Thus, the observed changes in yeast communities in urban soils could be a short-time response of the microbial community to a reduction in household waste.

Isolation of Culturable Yeasts and Molds from Soils to Investigate Fungal Population Structure.

Soil is host to an incredible amount of microbial life, with each gram containing up to billions of bacterial, archaeal, and fungal cells. Multicellular fungi such as molds and unicellular fungi, broadly defined as yeasts, fulfill essential roles in soil ecosystems as decomposers of organic material and as food sources for other soil dwellers. Fungal species diversity in soil is dependent on a multitude of climatic factors such as rainfall and temperature, as well as soil properties including organic matter, pH, and moisture. Lack of adequate environmental sampling, especially in regions of Asia, Africa, South America, and Central America, hinders the characterization of soil fungal communities and the discovery of novel species. We characterized soil fungal communities in nine countries across six continents using ~4,000 soil samples and a protocol developed in the laboratory for the isolation of yeasts and molds. This protocol begins with separate selective enrichment for yeasts and the medically relevant mold Aspergillus fumigatus, in liquid media while inhibiting bacterial growth. Resulting colonies are then transferred to solid media and further processed to obtain pure cultures, followed by downstream genetic characterization. Yeast species identity is established via sequencing of their internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene cluster, while global population structure of A. fumigatus is explored via microsatellite marker analysis. The protocol was successfully applied to isolate and characterize soil yeast and A. fumigatus populations in Cameroon, Canada, China, Costa Rica, Iceland, Peru, New Zealand, and Saudi Arabia. These findings revealed much-needed insights on global patterns in soil yeast diversity, as well as global population structure and antifungal resistance profiles of A. fumigatus. This paper presents the method of isolating both yeasts and A. fumigatus from international soil samples.

Soil yeasts promoting plant growth: benefits for the development of common wheat and white mustard

Soil yeasts promoting plant growth: benefits for the development of common wheat and white mustard

Plant Growth Promoting Activity and Biocontrol Potential of Soil Yeast

Among soil microorganisms, yeasts have received little attention as bioonoculant and biocontrol agents in comparison to bacterial, actinomycetes, and filamentous fungal antagonists. The ability of certain taxa of yeasts to multiply rapidly, to produce antibiotics and cell wall-degrading enzymes, to induce resistance of host tissues, and to produce plant growth regulators indicates the potential to exploit them as biocontrol agents and plant growth promoters. We investigated the ability of the soil yeast Rhodotorula sp. and Candida tropicalis to stimulate plant growth promoting characters and biocontrol potential. In vitro culture experiments found that Rhodotorula sp. SY3 (623.14 ug/ml with tryptophan: 150.12 ug/ml without tryptophan) and Candida tropicalis SY5 (580.25 ug/ml - with tryptophan: 120.24 ug/ml - without tryptophan) produces large quantities of indole acetic acid (IAA), but grows rapidly on aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, indicative of high ACC deaminase activity.