Isolation and biological activities of an endophytic Mortierella alpina strain from the Antarctic moss Schistidium antarctici

Reviewing bryophyte-microorganism association: insights into environmental optimization

Bryophytes, the second-largest group of plants, play a crucial role as early colonizers of land and are a prolific source of naturally occurring substances with significant economic potential. Microorganisms, particularly bacteria, cyanobacteria, fungi form intricate associations with plants, notably bryophytes, contributing to the ecological functioning of terrestrial ecosystems and sometimes it gives negative impact also. This review elucidates the pivotal role of endophytic bacteria in promoting plant growth, facilitating nutrient cycling, and enhancing environmental health. It comprehensively explores the diversity and ecological significance of fungal and bacterial endophytes across various ecosystems. Furthermore, it highlights the moss nitrogen dynamics observed in select moss species. Throughout the review, emphasis is placed on the symbiotic interdependence between bryophytes and microorganisms, offering foundational insights for future research endeavors. By shedding light on the intricate bryophyte-microorganism associations, this study advances our understanding of the complex interplay between plants, microbes, and their environment, paving the way for further research and applications in environmental and biotechnological realms.

Microbial successional pattern along a glacier retreat gradient from Byers Peninsula, Maritime Antarctica

The retreat of glaciers in Antarctica has increased in the last decades due to global climate change, influencing vegetation expansion, and soil physico-chemical and biological attributes. However, little is known about soil microbiology diversity in these periglacial landscapes. This study characterized and compared bacterial and fungal diversity using metabarcoding of soil samples from the Byers Peninsula, Maritime Antarctica. We identified bacterial and fungal communities by amplification of bacterial 16 S rRNA region V3-V4 and fungal internal transcribed spacer 1 (ITS1). We also applied 14C dating on soil organic matter (SOM) from six profiles. Physico-chemical analyses and attributes associated with SOM were evaluated. A total of 14,048 bacterial ASVs were obtained, and almost all samples had 50% of their sequences assigned to Actinobacteriota and Proteobacteria. Regarding the fungal community, Mortierellomycota, Ascomycota and Basidiomycota were the main phyla from 1619 ASVs. We found that soil age was more relevant than the distance from the glacier, with the oldest soil profile (late Holocene soil profile) hosting the highest bacterial and fungal diversity. The microbial indices of the fungal community were correlated with nutrient availability, soil reactivity and SOM composition, whereas the bacterial community was not correlated with any soil attribute. The bacterial diversity, richness, and evenness varied according to presence of permafrost and moisture regime. The fungal community richness in the surface horizon was not related to altitude, permafrost, or moisture regime. The soil moisture regime was crucial for the structure, high diversity and richness of the microbial community, specially to the bacterial community. Further studies should examine the relationship between microbial communities and environmental factors to better predict changes in this terrestrial ecosystem.

Identification and Biological Characteristics of Mortierella alpina Associated with Chinese Flowering Cherry (Cerasus serrulata) Leaf Blight in China

The Chinese flowering cherry (Cerasus serrulata), an ornamental tree with established medicinal values, is observed to suffer from leaf blight within Xi'an's greenbelts. This disease threatens both the plant's growth and its ornamental appeal. In this study, 26 isolates were obtained from plants with typical leaf blight, and only 3 isolates (XA-10, XA-15, and XA-18) were found to be pathogenic, causing similar symptoms on the leaves of the host plant. Based on sequence alignment, the ITS and LSU sequences of the three selected isolates were consistent, respectively. Following morphological and molecular analyses, the three selected isolates were further identified as Mortierella alpina. The three selected isolates exhibited similar morphological characteristics, including wavy colonies with dense, milky-white aerial mycelia on PDA medium. Therefore, isolate XA-10 was used as a representative strain for subsequent experiments. The representative strain XA-10 was found to exhibit optimal growth at a temperature of 30 °C and a pH of 7.0. Host range infection tests further revealed that the representative strain XA-10 could also inflict comparable disease symptoms on both the leaves and fruits of three different Rosaceae species (Prunus persica, Pyrus bretschneideri, and Prunus salicina). This study reveals, for the first time, the causative agent of leaf blight disease affecting the Chinese flowering cherry. This provides a deeper understanding of the biology and etiology of M. alpina. This study lays a solid foundation for the sustainable control and management of leaf blight disease in the Chinese flowering cherry.

Changes in Diversity and Composition of Rhizosphere Bacterial and Fungal Community between Resistant and Susceptible Pakchoi under Plasmodiophora brassicae

Plasmodiophora brassicae (P. brassicae) is a soil-born pathogen worldwide and can infect most cruciferous plants, which causes great yield decline and economic losses. It is not well known how microbial diversity and community composition change during P. brassicae infecting plant roots. Here, we employed a resistant and a susceptible pakchoi cultivar with and without inoculation with P. brassicae to analyze bacterial and fungal diversity using 16S rRNA V3-V4 and ITS_V1 regions, respectively. 16S rRNA V3-V4 and ITS_V1 regions were amplified and sequenced separately. Results revealed that both fungal and bacterial diversity increased, and composition was changed in the rhizosphere soil of the susceptible pakchoi compared with the resistant cultivar. In the four groups of R_mock, S_mock, R_10d, and S_10d, the most relatively abundant bacterium and fungus was Proteobacteria, accounting for 61.92%, 58.17%, 48.64%, and 50.00%, respectively, and Ascomycota, accounting for 75.11%, 63.69%, 72.10%, and 90.31%, respectively. A total of 9488 and 11,914 bacteria were observed uniquely in the rhizosphere soil of resistant and susceptible pakchoi, respectively, while only 80 and 103 fungi were observed uniquely in the correlated soil. LefSe analysis showed that 107 and 49 differentially abundant taxa were observed in bacteria and fungi. Overall, we concluded that different pakchoi cultivars affect microbial diversity and community composition, and microorganisms prefer to gather around the rhizosphere of susceptible pakchoi. These findings provide a new insight into plant-microorganism interactions.

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

AIM

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.

METHODS AND RESULTS

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.

CONCLUSION

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.

Antifungal activity of cyclopaldic acid from Antarctic Penicillium against phytopathogenic fungi

Plant pathogens cause great economic losses in agriculture. To reduce damage, chemical pesticides have been frequently used, but these compounds in addition to causing risks to the environment and health, its continuous use has given rise to resistant phytopathogens, threatening the efficiency of control methods. One alternative for such a problem is the use of natural products with high antifungal activity and low toxicity. Here, we present the production, isolation, and identification of cyclopaldic acid, a bioactive compound produced by Penicillium sp. CRM 1540, a fungal strain isolated from Antarctic marine sediment. The crude extract was fractionated by reversed-phase chromatography and yielded 40 fractions, from which fraction F17 was selected. We used 1D and 2D Nuclear Magnetic Resonance analysis in DMSO-d6 and CDCl3, together with mass spectrometry, to identify the compound as cyclopaldic acid C11H10O6 (238 Da). The pure compound was evaluated for antimicrobial activity against phytopathogenic fungi of global agricultural importance, namely: Macrophomina phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum. The antifungal assay revealed the potential of cyclopaldic acid, produced by Penicillium sp. CRM 1540, as a leading molecule against M. phaseolina and R. solani, with more than 90% of growth inhibition after 96h of contact with the fungal cells using 100 µg mL-1, and more than 70% using 50 µg mL-1.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03792-9.

Pyrrole-Based Enaminones as Building Blocks for the Synthesis of Indolizines and Pyrrolo[1,2-a]pyrazines Showing Potent Antifungal Activity

As a new approach, pyrrolo[1,2-a]pyrazines were synthesized through the cyclization of 2-formylpyrrole-based enaminones in the presence of ammonium acetate. The enaminones were prepared with a straightforward method, reacting the corresponding alkyl 2-(2-formyl-1H-pyrrol-1-yl)acetates, 2-(2-formyl-1H-pyrrol-1-yl)acetonitrile, and 2-(2-formyl-1H-pyrrol-1-yl)acetophenones with DMFDMA. Analogous enaminones elaborated from alkyl (E)-3-(1H-pyrrol-2-yl)acrylates were treated with a Lewis acid to afford indolizines. The antifungal activity of the series of substituted pyrroles, pyrrole-based enaminones, pyrrolo[1,2-a]pyrazines, and indolizines was evaluated on six Candida spp., including two multidrug-resistant ones. Compared to the reference drugs, most test compounds produced a more robust antifungal effect. Docking analysis suggests that the inhibition of yeast growth was probably mediated by the interaction of the compounds with the catalytic site of HMGR of the Candida species.

An assembled bacterial community associated with Artemisia annua L. causes plant protection against a pathogenic fungus

The microorganisms associated with a plant influence its growth and fitness. These microorganisms accumulate on the aerial and root surfaces of plants, as well as within the plants, as endophytes, although how the interaction between microorganisms protects the plant from pathogens is still little understood. In the current study, the impact of assembled the bacterial communities against the pathogenic fungus to promote Artemisia annua L. growths was investigated. We established a model of bacterium-fungus-plant system. Eight bacterial strains and a fungal pathogen Globisporangium ultimum (Glo) were isolated from wild A. annua roots and leaves, respectively. We assembled the six-bacteria community (C6: Rhizobium pusense, Paracoccus sp., Flavobacterium sp., Brevundimonas sp., Stenotrophomonas sp., and Bacillus sp.) with inhibition, and eight-bacteria community (C8) composing of C6 plus another two bacteria (Brevibacillus nitrificans and Cupriavidus sp.) without inhibition against Glo in individually dual culture assays. Inoculation of seedlings with C8 significantly reduced impact of Glo. The growth and disease suppression of A. annua seedlings inoculated with C8 + Glo were significantly better than those of seedlings inoculated with only Glo. C8 had more inhibitory effects on Glo, and also enhanced the contents of four metabolites in seedling roots compared to Glo treatment only. Additionally, the inhibitory effects of root extracts from A. annua seedlings showed that Glo was most sensitive, the degree of eight bacteria sensitivity were various with different concentrations. Our findings suggested that the non-inhibitory bacteria played a vital role in the bacterial community composition and that some bacterial taxa were associated with disease suppression. The construction of a defined assembled bacterial community could be used as a biological fungicide, promoting biological disease control of plants.

Phenolic Biotransformations in Wheatgrass Juice after Primary and Secondary Fermentation

Fermented wheatgrass juice was prepared using a two-stage fermentation process by employing Saccharomyces cerevisiae and recombinant Pediococcus acidilactici BD16 (alaD⁺). During fermentation, a reddish-brown hue appeared in wheatgrass juice due to production of different types of red pigments. The fermented wheatgrass juice has considerably higher content of anthocyanins, total phenols and beta-carotenes as compared to unfermented wheatgrass juice. It has low ethanol content, which might be ascribed to the presence of certain phytolignans in wheatgrass juice. Several yeast-mediated phenolic transformations (such as bioconversion of coumaric acid, hydroxybenzoic acid, hydroxycinnamic acid and quinic acid into respective derivatives; glycosylation and prenylation of flavonoids; glycosylation of lignans; sulphonation of phenols; synthesis of carotenoids, diarylnonanoids, flavanones, stilbenes, steroids, quinolones, di- and tri-terpenoids and tannin) were identified in fermented wheatgrass juice using an untargeted liquid chromatography (LC)-mass spectrometry (MS)-matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF)/time-of-flight (TOF) technique. The recombinant P. acidilactici BD16 (alaD⁺) also supported flavonoid and lignin glycosylation; benzoic acid, hydroxycoumaric acid and quinic acid derivatization; and synthesis of anthraquinones, sterols and triterpenes with therapeutic benefits. The information presented in this manuscript may be utilized to elucidate the importance of Saccharomyces cerevisiae and P. acidilactici BD16 (alaD⁺) mediated phenolic biotransformations in developing functional food supplements such as fermented wheatgrass juice.

Bioactive Compounds Produced by Endophytic Microorganisms Associated with Bryophytes—The “Bryendophytes”

The mutualistic coexistence between the host and endophyte is diverse and complex, including host growth regulation, the exchange of substances like nutrients or biostimulants, and protection from microbial or herbivore attack. The latter is commonly associated with the production by endophytes of bioactive natural products, which also possess multiple activities, including antibacterial, insecticidal, antioxidant, antitumor, and antidiabetic properties, making them interesting and valuable model substances for future development into drugs. The endophytes of higher plants have been extensively studied, but there is a dearth of information on the biodiversity of endophytic microorganisms associated with bryophytes and, more importantly, their bioactive metabolites. For the first time, we name bryophyte endophytes “bryendophytes” to elaborate on this important and productive source of biota. In this review, we summarize the current knowledge on the diversity of compounds produced by endophytes, emphasizing bioactive molecules from bryendophytes. Moreover, the isolation methods and biodiversity of bryendophytes from mosses, liverworts, and hornworts are described.

The core fungal microbiome of banana (Musa spp.)

Here, we report a metabarcoding (ITS2) study to define the common core fungal microbiome (mycobiome) of healthy Musa spp. (bananas and plantains). To identify a list of 21 core fungal taxa, we first characterised the effects of edaphic conditions and host genotype – two factors that are likely to differ between farms – on the diversity of fungal communities in bulk soil and seven plant compartments. This experiment facilitated shortlisting of core ‘candidates’, which were then elevated to full core status if also found to frequent a wide-range of field-grown Musa spp. and exhibit hub-like characteristics in network analyses. Subsequently, we conducted a meta-analysis of eleven publicly available datasets of Musa spp. associated fungi demonstrating that the core fungi identified in our study have close relatives in other countries. The diversity and composition of mycobiomes differed between plant compartments and soils, but not genotypes. The core mycobiome included Fusarium oxysporum and its relatives, which dominated all plant compartments, as well as members of the Sordariomycetes, Dothideomycetes, and Mortierellomycota. Our study provides a robust list of common core fungal taxa for Musa spp. Further studies may consider how changes in the frequencies and activities of these taxa influence host fitness and whether they can be managed to improve banana production.

Ecological Characteristics of Antarctic Fungi

In view of the high responsiveness of polar ecosystems to the global climate change, the research of Antarctic microorganisms has become a topical issue. The unique ecosystems that have developed under the severe climate conditions of the continent lack flowering plants but are dominated by soil mycobiota. In addition to performing their classical ecological functions, Antarctic fungi form the basis of local communities, e.g., endoliths and microbial mats. Furthermore, Antarctic fungi are a major force that mediates transformation of rock minerals in situ and makes biologically significant elements available for other organisms. For these reasons, mycobiota plays a central role in the maintenance of ecological equilibrium in Antarctica. The dominant fungal division on the continent is Ascomycota (77.1%), and not Basidiomycota (9.1%), as it is the case on other continents. For a number of reasons, yeasts and yeast-like micromycetes (mainly basidiomycetes) are more tolerant to extreme conditions in various Antarctic biotopes than filamentous fungi. Substantial evidence suggests that filamentous fungi and yeasts are better adapted to existence in ecosystems with extremely low temperatures than other microorganisms. Due to the long-term isolation of Antarctica from other continents, local biota has been evolving largely independently, which led to emergence of multiple endemic fungal taxa. The presence of eurytopes on the continent is presumably related to the global warming and growing anthropogenic pressure. This review discusses the current state of research on the structure of fungal communities of Antarctic subaerial and subaquatic biotopes, the ecological role of yeast-mycelial dimorphism in Antarctic fungi, the problem of endemism of Antarctic mycobiota, as well as the ecological and physiological adaptations of fungi to low temperatures; it also justifies the relevance of research into secondary metabolites of psychrophilic micromycetes.

Fungi-Bacteria Associations in Wilt Diseased Rhizosphere and Endosphere by Interdomain Ecological Network Analysis

In the plant rhizosphere and endosphere, some fungal and bacterial species regularly co-exist, however, our knowledge about their co-existence patterns is quite limited, especially during invasion by bacterial wilt pathogens. In this study, the fungal communities from soil to endophytic compartments were surveyed during an outbreak of tobacco wilt disease caused by Ralstonia solanacearum. It was found that the stem endophytic fungal community was significantly altered by pathogen invasion in terms of community diversity, structure, and composition. The associations among fungal species in the rhizosphere and endosphere infected by R. solanacearum showed more complex network structures than those of healthy plants. By integrating the bacterial dataset, associations between fungi and bacteria were inferred by Inter-Domain Ecological Network (IDEN) approach. It also revealed that infected samples, including both the rhizosphere and endosphere, had more complex interdomain networks than the corresponding healthy samples. Additionally, the bacterial wilt pathogenic Ralstonia members were identified as the keystone genus within the IDENs of both root and stem endophytic compartments. Ralstonia members was negatively correlated with the fungal genera Phoma, Gibberella, and Alternaria in infected roots, as well as Phoma, Gibberella, and Diaporthe in infected stems. This suggested that those endophytic fungi may play an important role in resisting the invasion of R. solanacearum.

Effect of a Wood-Based Carrier of Trichoderma atroviride SC1 on the Microorganisms of the Soil

Wood pellets can sustain the growth of Trichoderma spp. in soil; however, little is known about their side effects on the microbiota. The aims of this study were to evaluate the effect of wood pellets on the growth of Trichoderma spp. in bulk soil and on the soil microbial population's composition and diversity. Trichoderma atroviride SC1 coated wood pellets and non-coated pellets were applied at the level of 10 g∙kg-1 of soil and at the final concentration of 5 × 103 conidia∙g-1 of soil and compared to a conidial suspension applied at the same concentration without the wood carrier. Untreated bulk soil served as a control. The non-coated wood pellets increased the total Trichoderma spp. population throughout the experiment (estimated as colony-forming unit g-1 of soil), while wood pellets coated with T. atroviride SC1 did not. The wood carrier increased the richness, and temporarily decreased the diversity, of the bacterial population, with Massilia being the most abundant bacterial genus, while it decreased both the richness and diversity of the fungal community. Wood pellets selectively increased fungal species having biocontrol potential, such as Mortierella, Cladorrhinum, and Stachybotrys, which confirms the suitability of such carriers of Trichoderma spp. for soil application.

Contrasting early successional dynamics of bacterial and fungal communities in recently deglaciated soils of the maritime Antarctic

Although microorganisms are the very first colonizers of recently deglaciated soils even prior to plant colonization, the drivers and patterns of microbial community succession at early-successional stages remain poorly understood. The successional dynamics and assembly processes of bacterial and fungal communities were compared on a glacier foreland in the maritime Antarctic across the ~10-year soil-age gradient from bare soil to sparsely vegetated area. Bacterial communities shifted more rapidly than fungal communities in response to glacial retreat; species turnover (primarily the transition from glacier- to soil-favouring taxa) contributed greatly to bacterial beta diversity, but this pattern was less clear in fungi. Bacterial communities underwent more predictable (more deterministic) changes along the soil-age gradient, with compositional changes paralleling the direction of changes in soil physicochemical properties following deglaciation. In contrast, the compositional shift in fungal communities was less associated with changes in deglaciation-induced changes in soil geochemistry and most fungal taxa displayed mosaic abundance distribution across the landscape, suggesting that the successional dynamics of fungal communities are largely governed by stochastic processes. A co-occurrence network analysis revealed that biotic interactions between bacteria and fungi are very weak in early succession. Taken together, these results collectively suggest that bacterial and fungal communities in recently deglaciated soils are largely decoupled from each other during succession and exert very divergent trajectories of succession and assembly under different selective forces.

Drought Exposed Burkholderia seminalis JRBHU6 Exhibits Antimicrobial Potential Through Pyrazine-1,4-Dione Derivatives Targeting Multiple Bacterial and Fungal Proteins

The present study aimed to explore the antimicrobial potentials of soil bacteria and identify the bioactive compounds and their likely targets through in silico studies. A total 53 bacterial isolates were screened for their antimicrobial potential of which the strain JRBHU6 showing highest antimicrobial activity was identified as Burkholderia seminalis (GenBank accession no. MK500868) based on 16S ribosomal RNA (rRNA) gene sequencing and phylogenetic analysis. B. seminalis JRBHU6 also produced hydrolytic enzymes chitinases and cellulase of significance in accrediting its antimicrobial nature. The bioactive metabolites produced by the isolate were extracted in different organic solvents among which methanolic extract showed best growth-suppressing activities toward multidrug resistant Staphylococcus aureus and fungal strains, viz Fusarium oxysporum, Aspergillus niger, Microsporum gypseum, Trichophyton mentagrophytes, and Trichoderma harzianum. The antimicrobial compounds were purified using silica gel thin layer chromatography and high-performance liquid chromatography (HPLC). On the basis of spectroscopic analysis, the bioactive metabolites were identified as pyrrolo(1,2-a)pyrazine-1,4-dione,hexahydro (PPDH) and pyrrolo(1,2-a)pyrazine-1,4-dione, hexahydro-3(2-methylpropyl) (PPDHMP). In silico molecular docking studies showed the bioactive compounds targeting fungal and bacterial proteins, among which PPDHMP was multitargeting in nature as reported for the first time through this study.

Newly Isolated Streptomyces sp. JBS5-6 as a Potential Biocontrol Agent to Control Banana Fusarium Wilt: Genome Sequencing and Secondary Metabolite Cluster Profiles

Banana is a key staple food and fruit in countries all over the world. However, the development of the global banana industry is seriously threatened by Fusarium wilt disease, which is caused by Fusarium oxysporum f. sp. cubense (Foc). In particular, Foc tropical race 4 (Foc TR4) could infect more than 80% of global banana and plantain crops. Until now, there were no commercial chemicals or resistant cultivars available to control the disease. Biological control using actinomycetes is considered a promising strategy. In this study, 88 actinomycetes were isolated from a banana orchard without symptoms of Fusarium wilt disease for more than 10 years. An actinobacterial strain labeled as JBS5-6 has exhibited strong antifungal activities against Foc TR4 and other selected 10 phytopathogenic fungi. Based on phenotypic and biochemical traits as well as complete genome analysis, strain JBS5-6 was assigned to Streptomyces violaceusniger. Extracts of the strain inhibited the mycelial growth and spore germination of Foc TR4 by destroying membrane integrity and the ultrastructure of cells. The complete genome of strain JBS5-6 was sequenced and revealed a number of key function gene clusters that contribute to the biosynthesis of active secondary metabolites. Sixteen chemical compounds were further identified by gas chromatography-mass spectrometry (GC-MS). 5-hydroxymethyl-2-furancarboxaldehyde was one of the dominant components in strain JBS5-6 extracts. Moreover, fermentation broth of strain JBS5-6 significantly reduced the disease index of banana seedlings by inhibiting the infection of Foc TR4 in a pot experiment. Hence, strain JBS5-6 is a potential biocontrol agent for the management of disease and the exploitation of biofertilizer.

Gut mycobiomes are altered in people with type 2 Diabetes Mellitus and Diabetic Retinopathy

Studies have documented dysbiosis in the gut mycobiome in people with Type 2 diabetes mellitus (T2DM). However, it is not known whether dysbiosis in the gut mycobiome of T2DM patients would be reflected in people with diabetic retinopathy (DR) and if so, is the observed mycobiome dysbiosis similar in people with T2DM and DR. Gut mycobiomes were generated from healthy controls (HC), people with T2DM and people with DR through Illumina sequencing of ITS2 region. Data were analysed using QIIME and R software. Dysbiotic changes were observed in people with T2DM and DR compared to HC at the phyla and genera level. Mycobiomes of HC, T2DM and DR could be discriminated by heat map analysis, Beta diversity analysis and LEfSE analysis. Spearman correlation of fungal genera indicated more negative correlation in HC compared to T2DM and DR mycobiomes. This study demonstrates dysbiosis in the gut mycobiomes in people with T2DM and DR compared to HC. These differences were significant both at the phyla and genera level between people with T2DM and DR as well. Such studies on mycobiomes may provide new insights and directions to identification of specific fungi associated with T2DM and DR and help developing novel therapies for Diabetes Mellitus and DR.

Soil stabilisation for DNA metabarcoding of plants and fungi. Implications for sampling at remote locations or via third-parties

Storage of soil samples prior to metagenomic analysis presents a problem. If field sites are remote or if samples are collected by third parties, transport to analytical laboratories may take several days or even weeks. The bulk of such samples and requirement for later homogenisation precludes the convenient use of a stabilisation buffer, so samples are usually cooled or frozen during transit. There has been limited testing of the most appropriate storage methods for later study of soil organisms by eDNA approaches. Here we tested a range of storage methods on two contrasting soils, comparing these methods to the control of freezing at -80 °C, followed by freeze-drying. To our knowledge, this is the first study to examine the effect of storage conditions on eukaryote DNA in soil, including both viable organisms (fungi) and DNA contained within dying/dead tissues (plants). For fungi, the best storage regimes (closest to the control) were storage at 4 °C (for up to 14 d) or active air-drying at room temperature. The worst treatments involved initial freezing, followed by thawing which led to significant later spoilage. The key spoilage organisms were identified as Metarhizium carneum and Mortierella spp., with a general increase in saprotrophic fungi and reduced abundances of mycorrhizal/biotrophic fungi. Plant data showed a similar pattern, but with greater variability in community structure, especially in the freeze-thaw treatments, probably due to stochastic variation in substrates for fungal decomposition, algal proliferation and some seed germination. In the absence of freeze drying facilities, samples should be shipped refrigerated, but not frozen if there is any risk of thawing.

Isolation and Molecular Characterization of Antibiotic Producing Bacillus licheniformis Strains Isolated from Soil

Currently, there is an increase prevalence of antibiotic-resistant bacteria worldwide. Therefore, the need for characterization of naturally occuring antibiotics with less antibiotic resistance is required. Soil resources contains valuable antibiotic producing microorganisms that increasingly being utilized for the production of suitable antibiotics. Therefore, this study aimed at identifying an antibiotic bacteria with ability of producing antibiotic that is isolated from soil samples collected from Al Zarqa provenance, an arid area in Jordan. Morphological and biochemical characterization of the isolates were carried out and found that all of the isolates belong to Bacillus genus. Further confirmation of the characterization of the bacteria was done by ribosomal RNA and PCR. The results reveal that the isolates represent Basilluslicheniformis. These bacilli were further investigated for antimicrobial activities against 6 ATCC human pathogens viz., S. aureus, S. pneumonia, Salmonella typhi., E. coli, P. mirabels and E. cloacae. Additionally, the results of Gas Chromatography Mass Spectrometry (GCMS) of ethyl acetate extracts for B. licheniformis secondary metabolites showed that they contain two main antimicrobial compounds namely Pyrrolo [1, 2-a] pyrazine-1, 4-dione,hexahydro and Trans-13-octadecenoic acid. The present work maybe suggests that soil isolates from the studied arid area include antibiotic producing strains that can be utilized commercially.

Extracellular Enzymes and Bioactive Compounds from Antarctic Terrestrial Fungi for Bioprospecting

Antarctica, one of the harshest environments in the world, has been successfully colonized by extremophilic, psychrophilic, and psychrotolerant microorganisms, facing a range of extreme conditions. Fungi are the most diverse taxon in the Antarctic ecosystems, including soils. Genetic adaptation to this environment results in the synthesis of a range of metabolites, with different functional roles in relation to the biotic and abiotic environmental factors, some of which with new biological properties of potential biotechnological interest. An overview on the production of cold-adapted enzymes and other bioactive secondary metabolites from filamentous fungi and yeasts isolated from Antarctic soils is here provided and considerations on their ecological significance are reported. A great number of researches have been carried out to date, based on cultural approaches. More recently, metagenomics approaches are expected to increase our knowledge on metabolic potential of these organisms, leading to the characterization of unculturable taxa. The search on fungi in Antarctica deserves to be improved, since it may represent a useful strategy for finding new metabolic pathways and, consequently, new bioactive compounds.

Diversity and distribution of cultivable fungi present in acid sulphate soils in chronosequence under para-periglacial conditions in King George Island, Antarctica

We recovered 85 fungal isolates from the acid sulphate soils in chronosequence under para-periglacial conditions in King George Island, Antarctica. Thirty-two taxa belonging to the phylum Ascomycota, Basidiomycota and Mortierellomycota were identified. Mortierella amoeboidea, Mortierella sp. 2, Mortierella sp. 3, Penicillium sp. 2 and Penicillium sp. 3 dominated the sulphite soils. Despite the multi-extreme physic-chemical conditions of the sulphate soils (low pH, variable content of macro and micronutrients and organic matter), the fungal assemblages exhibited moderate diversity indices, which ranged according to the degree of soil development. Soils with more weathered and, consequently, with highest values of organic carbon shelter the most diverse fungal assemblages, which can be associated with the occurrence of sulphurisation and sulphide oxidation. Different taxa of Mortierella and Penicillium displayed broad pH (3-9) and temperature (5-35 °C) plasticity. The multi-extreme sulphite soils of Antarctica revealed the presence of moderate fungal diversity comprising cold cosmopolitan and psychrophilic endemic taxa. Among these, Mortierella and Penicillium, known to survive in extreme conditions such as low temperature and available organic matter, low pH and high concentrations of metals, might represent interesting techniques to be used in biotechnological processes such as bioleaching in metallurgy and phosphate solubilisation in agriculture.

Organic Fertilization Assembles Fungal Communities of Wheat Rhizosphere Soil and Suppresses the Population Growth of Heterodera avenae in the Field

Heterodera avenae (cereal cyst nematode, CCN) infects wheat and other cereal crops and causes severe losses in their yield. Research has shown that CCN infestations can be mitigated by organic fertilization in wheat fields, but the mechanisms underlying this phenomenon are still largely unknown. In this study, the relationships among CCN, soil properties, and soil fungal communities with organic fertilizer (OF) or chemical fertilizer (CF) and without fertilizer (CK), were investigated for two years in a wheat field in Henan province, China. Our results showed that the concentrations of soil total N, total P, available P, available K, and organic matter were all promoted by the OF treatment at the jointing stage of wheat, coinciding with the peak in egg hatching and penetration of wheat root by CCNs. Soil total N correlated positively (R² = 0.759, p < 0.05) with wheat yields but negatively (R² = 0.663, p < 0.01) with Pf/Pi (index of cyst nematode reproduction), implying the regulated soil property contributes to suppressing CCN in the OF treatment. Furthermore, fungal community α-diversity (Shannon and Simpson) and β-diversity (PCoA) of rhizosphere soil was improved under the organic fertilizer treatment. The fungal genera negatively associated with the Pf/Pi of CCN were highly enriched, which included Mortierella and Chaetomium, two taxa already reported as being nematophagous fungi in many other studies. These two genera were heavily surrounded by much more related fungal genera in the constructs co-occurrence network. These results suggested that the OF treatment shifted soil fungal community functioning towards the suppression of CCN. Taken together, the suppressed cyst nematode reproduction with the assembly of fungal communities in the rhizosphere led to greater wheat yields under organic fertilization. These findings provide an in-depth understanding of the benefits provided by organic fertilization for developing sustainable agriculture.

Fungal Community in Antarctic Soil Along the Retreating Collins Glacier (Fildes Peninsula, King George Island)

Glacial retreat is one of the most conspicuous signs of warming in Antarctic regions. Glacier soils harbor an active microbial community of decomposers, and under the continuous retraction of glaciers, the soil starts to present a gradient of physical, chemical, and biological factors reflecting regional changes over time. Little is known about the biological nature of fungi in Antarctic glacier soils. In this sense, this work aimed at studying the behavior of fungal community structure from samples of glacier soil collected after glacial retreat (Collins Glacier). A total of 309 fungi distributed in 19 genera were obtained from eleven soil samples. Representatives of the genera Pseudogymnoascus (Ascomycota) and Mortierella (Mortierellomycota) were the most abundant isolates in all samples. The data revealed the presence of filamentous fungi belonging to the phylum Basidiomycota, rarely found in Antarctica. Analysis of the generalized linear models revealed that the distance from the glacier as well as phosphorus and clay were able to modify the distribution of fungal species. Environmental variations proved to have influenced the genera Pseudogymnoascus and Pseudeutorium.

Diversity, distribution, and ecology of viable fungi in permafrost and active layer of Maritime Antarctica

We evaluated the diversity and distribution of viable fungi present in permafrost and active layers obtained from three islands of Maritime Antarctica. A total of 213 fungal isolates were recovered from the permafrost, and 351 from the active layer, which were identified in 58 taxa; 27 from permafrost and 31 from the active layer. Oidiodendron, Penicillium, and Pseudogymnoascus taxa were the most abundant in permafrost. Bionectriaceae, Helotiales, Mortierellaceae, and Pseudeurotium were the most abundant in the active layer. Only five shared both substrates. The yeast Mrakia blollopis represented is the first reported on Antarctic permafrost. The fungal diversity detected was moderate to high, and composed of cosmopolitan, cold-adapted, and endemic taxa, reported as saprobic, mutualistic, and parasitic species. Our results demonstrate that permafrost shelters viable fungi across the Maritime Antarctica, and that they are contrasting to the overlying active layer. We detected important fungal taxa represented by potential new species, particularly, those genetically close to Pseudogymnoascus destructans, which can cause extinction of bats in North America and Eurasia. The detection of viable fungi trapped in permafrost deserves further studies on the extension of its fungal diversity and its capability to expand from permafrost to other habitats in Antarctica, and elsewhere.

Diversity and bioprospecting of cultivable fungal assemblages in sediments of lakes in the Antarctic Peninsula

We recovered 195 fungal isolates from the sediments of different lakes in the Antarctic Peninsula, which were screened to detect bioactive compounds. Forty-two taxa belonging to the phyla Ascomycota, Basidiomycota, and Mortierellomycota were identified. Thelebolus globosus, Antarctomyces psychrotrophicus, Pseudogymnoascus verrucosus, Vishniacozyma victoriae, and Phenoliferia sp. were found to be the most prevalent. The fungal assemblages showed high diversity and richness, but low dominance values. However, the diversity indices and fungal distribution ranged according to the different lake sediments. Sixty fungal extracts displayed at least one biological activity against the evaluated targets. Among them, Pseudogymnoascus destructans showed selective trypanocidal activity, Cladosporium sp. 1 and Trichoderma polysporum showed antifungal activity, and Pseudogymnoascus appendiculatus and Helotiales sp. showed high herbicidal activity. We detected a rich and diverse fungal community composed of cold cosmopolitan and psychrophilic endemic taxa recognized as decomposers, symbiotics, pathogens, and potential new species, in the sediments of Antarctic lakes. The dynamics and balance of this fungal community represents an interesting aquatic web model for further ecological and evolutionary studies under extreme conditions and potential climate changes in the regions. In addition, we detected fungal taxa and isolates able to produce bioactive compounds that may represent the source of prototype molecules for applications in medicine and agriculture.

The plant organs and rhizosphere determine the common bean mycobiome

The plant microbiota diversity is often underestimated when approaches developed mainly for the identification of cultivable microorganisms are used. High-throughput sequencing allows a deeper understanding of the microbial diversity associated with plants. The amplification of ITS1 was used to analyze fungal diversity in several plant organs and rhizosphere of three common bean (Phaseolus vulgaris) varieties grown in a greenhouse. The fungal diversity diverged between those plant organs and the rhizosphere, with the highest found in the rhizosphere and the lowest in the stem. In each organ different numbers of genus, OTUs were identified, in a total of 283 OTUs evenly distributed among the varieties. In the co-occurrence network, a larger number of positive interactions were found in the organs of the aerial part in all varieties. We observed that the diversity of the endophytic microbiota differed more between plant organs than between common bean varieties. Our results show that the diversity of endophytic fungi can be efficiently accessed with the sequencing of ITS amplicons and that this diversity may vary among distinct plant organs and the rhizosphere of a single plant variety.

Symbiotic microbes of Saxifraga stellaris ssp. alpigena from the copper creek of Schwarzwand (Austrian Alps) enhance plant tolerance to copper

Saxifraga stellaris var. alpigena grows as one of the very few higher plants in the copper rich area of the "blue creek" in Austria. Two endophytes were isolated from it: Mortierella sp. (fungus), and Stenotrophomonas maltophilia (bacterium). Both microbes were practically inseparable due to resistance of the bacteria to the antibiotics tested. On PDA media, the fungus showed higher tolerance to copper than the bacterium, which disappeared from both the media and the surface of the fungus in the presence of 150 μM of Cu. However, at this Cu concentration, the bacteria were still detectable inside the mycelium and reappeared on the outside when transferred to media of lower Cu concentration. Microscopic studies of in vitro cultivated plants showed that the fungus was present in both, the roots and shoots of the plant. The effects of endophytes on plant performance were assessed in rhizoboxes filled with Cu-rich substratum; plants inoculated with both microbes showed better growth, survival and photosynthesis performance than the non-inoculated controls. The results of this study prove the beneficial influence of the isolated endophytes on the Cu tolerance of S. stellaris, and indicate the ecological potential of applying microbial consortia to plants under extreme environmental conditions.

Taxonomy and Broad-Spectrum Antifungal Activity of Streptomyces sp. SCA3-4 Isolated From Rhizosphere Soil of Opuntia stricta

Actinobacteria are important producers of bioactive compounds. Extreme ecosystems cause evolution of novel secondary metabolic pathways of Actinobacteria and increase the possible discovery of new biological functions of bioactive compounds. Here, we isolated 65 Actinobacteria from rhizosphere soil samples of Opuntia stricta. An Actinobacteria strain (named SCA3-4) was screened against Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4, ATCC 76255). The strain produced pink-white aerial mycelia and brown substrate mycelium on Gause No. 1 agar. Biverticillate chains of cylindrical spores were observed by scanning electron microscopy (SEM). Based on alignment of 16S rRNA sequences, a constructed phylogenetic tree showed that strain SCA3-4 shared a 99.54% similarity with Streptomyces lilacinus NRRL B-1968T. The morphological, biochemical, physiological, and molecular characteristics further indicated that strain SCA3-4 belongs to the Streptomyces sp. It can grow well on medium with the following antibiotics chloramphenicol, streptomycin, penicillin-G, gentamicin, erythromycin, nystatin or neomycin sulfate. The polymerase chain reaction (PCR) amplification of types I and II polyketide synthase genes (PKS-I and PKS-II) suggested its bioactive potential. Under treatment with 100 μg/ml of ethyl acetate extracts isolated from Streptomyces sp. SCA3-4, growth of Foc TR4 was inhibited and cell membrane was destroyed. Crude extracts also showed a broad-spectrum antifungal activity against 13 phytopathogenic fungi including Foc TR4 and displayed the lowest minimum inhibitory concentration (MIC) (0.781 μg/ml) against Colletotrichum fragariae (ATCC 58718). A total of 21 different compounds identified by gas chromatography-mass spectrometry (GC-MS) were composed of phenolic compound, pyrrolizidine, hydrocarbons, esters, and acids. Besides the known active compounds, Streptomyces sp. SCA3-4 possesses antimicrobial or other biological activities. Further attention will be paid on other compounds with no functional annotation, aiming at the discovery of new bioactive substances.

Infection of Plasmodiophora brassicae changes the fungal endophyte community of tumourous stem mustard roots as revealed by high-throughput sequencing and culture-dependent methods

Diverse fungal endophytes live in plants and are shaped by some abiotic and biotic stresses. Plant disease as particular biotic stress possibly gives an impact on the communities of fungal endophytes. In this study, clubroot disease caused by an obligate biotroph protist, Plasmodiophora brassicae, was considered to analyze its influence on the fungal endophyte community using an internal transcribed spacer (ITS) through high-throughput sequencing and culture-dependent methods. The results showed that the diversity of the endophyte community in the healthy roots was much higher than the clubroots. Ascomycota was the dominant group of endophytes (Phoma, Mortierella, Penicillium, etc.) in the healthy roots while P. brassicae was the dominant taxon in the clubroots. Hierarchical clustering, principal component analysis (PCA), principal coordinates analysis (PCoA) and analysis of similarities (ANOSIM) indicated significant differences between the endophyte communities in the healthy roots and clubroots. Linear discriminant analysis effect size (LefSe) analysis showed that the dominant genera could be regarded as potential biomarkers. The endophyte community in the healthy roots had a more complex network compared with the clubroots. Also, many plant pathogenic Fusarium were isolated from the clubroots by the culture-dependent method. The outcome of this study illustrates that P. brassicae infection may change the fungal endophyte community associated with the roots of tumourous stem mustard and facilitates the entry of soil pathogen into the roots.

The Beneficial Root-Colonizing Fungus Mortierella hyalina Promotes the Aerial Growth of Arabidopsis and Activates Calcium-Dependent Responses That Restrict Alternaria brassicae-Induced Disease Development in Roots

The endophytic fungus Mortierella hyalina colonizes the roots of Arabidopsis thaliana and stimulates growth and biomass production of the aerial parts but not of roots. An exudate fraction from the fungus induces rapid and transient cytoplasmic Ca²⁺elevation in the roots. The Ca²⁺ response does not require the well-characterized (co)receptors BAK1, CERK1, and FLS2 for pathogen-associated molecular patterns, and the Ca²⁺ channels GLR-2.4, GLR-2.5, and GLR-3.3 or the vacuolar TWO PORE CHANNEL1, which might be involved in cytoplasmic Ca²⁺ elevation. We isolated an ethyl-methane-sulfonate-induced Arabidopsis mutant that is impaired in this Ca²⁺ response. The roots of the mutant are impaired in M. hyalina-mediated suppression of immune responses after Alternaria brassicae infection, i.e., jasmonate accumulation, generation of reactive oxygen species, as well as the activation of jasmonate-related defense genes. Furthermore, they are more colonized by M. hyalina than wild-type roots. We propose that the mutant gene product is involved in a Ca²⁺-dependent signaling pathway activated by M. hyalina to suppress immune responses in Arabidopsis roots.

Fungal Biosurfactants from Mortierella alpina

The zygomycete Mortierella alpina is a well-known producer of polyunsaturated fatty acids in the food industry. Two series of its secondary metabolites are reported: Malpinins, a family of amphiphilic acetylated hexapeptides, were chemically characterized and serve as natural emulsifiers during lipid secretion. Additionally, hydrophobic cyclopentapeptides, malpibaldins, were structurally elucidated by NMR experiments, and their absolute stereochemistry was elucidated through chemical derivatization and synthesis. This work highlights lower fungi as a novel reservoir for natural products.

Biodegradation of Remazol Brilliant Blue R using isolated bacterial culture (Staphylococcus sp. K2204)

Staphylococcus sp. K2204, a bacterial isolate, was employed in this work to decolorize Remazol Brilliant Blue R (RBBR), which belongs to the anthraquinone class of textile dye. Staphylococcus sp. K2204 biodegraded 100 mg/L RBBR at 37°C under static condition with the help of extracellular laccase and peroxidases. The products of RBBR degradation were characterized using analytical tools including mass spectral technique. The phytotoxicity tests evaluated the toxicity of RBBR and the products of biodegradation. The research outlined here is the first attempt to utilize Staphylococcus sp. K2204 for remediating the wastewater containing anthraquinone textile dye.

Synthesis of Indoleacetic Acid, Gibberellic Acid and ACC-Deaminase by Mortierella Strains Promote Winter Wheat Seedlings Growth under Different Conditions

The endogenous pool of phytoregulators in plant tissues supplied with microbial secondary metabolites may be crucial for the development of winter wheat seedlings during cool springs. The phytohormones may be synthesized by psychrotrophic microorganisms in lower temperatures occurring in a temperate climate. Two fungal isolates from the Spitzbergen soils after the microscopic observations and “the internal transcribed spacer” (ITS) region molecular characterization were identified as Mortierellaantarctica (MA DEM7) and Mortierella verticillata (MV DEM32). In order to study the synthesis of indoleacetic acid (IAA) and gibberellic acid (GA), Mortierella strains were grown on media supplemented with precursor of phytohormones tryptophan at 9, 15 °C, and 20 °C for nine days. The highest amount of IAA synthesis was identified in MV DEM32 nine-day-culture at 15 °C with 1.5 mM of tryptophan. At the same temperature (15 °C), the significant promoting effect (about 40% root and shoot fresh weight) of this strain on seedlings was observed. However, only MA DEM-7 had the ACC (1-aminocyclopropane-1-carboxylate) deaminase activity with the highest efficiency at 9 °C and synthesized IAA without tryptophan. Moreover, at the same conditions, the strain was confirmed to possess the strong promoting effect (about 40% root and 24% shoot fresh weight) on seedlings. Both strains synthesized GA in all tested terms and temperatures. The studied Mortierella strains had some important traits that led them to be considered as microbial biofertilizers components, improving plant growth in difficult temperate climates.

Antimycobacterial activity of an anthracycline produced by an endophyte isolated from Amphipterygium adstringens

The search for new compounds effective against Mycobacterium tuberculosis is still a priority in medicine. The evaluation of microorganisms isolated from non-conventional locations offers an alternative to look for new compounds with antimicrobial activity. Endophytes have been successfully explored as source of bioactive compounds. In the present work we studied the nature and antimycobacterial activity of a compound produced by Streptomyces scabrisporus, an endophyte isolated from the medicinal plant Amphipterygium adstringens. The active compound was detected as the main secondary metabolite present in organic extracts of the streptomycete and identified by NMR spectroscopic data as steffimycin B (StefB). This anthracycline displayed a good activity against M. tuberculosis H37Rv ATCC 27294 strain, with MIC₁₀₀ and SI values of 7.8 µg/mL and 6.42, respectively. When tested against the rifampin mono resistant M. tuberculosis Mtb-209 pathogen strain, a better activity was observed (MIC₁₀₀ of 3.9 µg/mL), suggesting a different action mechanism of StefB from that of rifampin. Our results supported the endophyte Streptomyces scabrisporus as a good source of StefB for tuberculosis treatment, as this anthracycline displayed a strong bactericidal effect against M. tuberculosis, one of the oldest and more dangerous human pathogens causing human mortality.

Network hubs in root-associated fungal metacommunities

BACKGROUND

Although a number of recent studies have uncovered remarkable diversity of microbes associated with plants, understanding and managing dynamics of plant microbiomes remain major scientific challenges. In this respect, network analytical methods have provided a basis for exploring "hub" microbial species, which potentially organize community-scale processes of plant-microbe interactions.

METHODS

By compiling Illumina sequencing data of root-associated fungi in eight forest ecosystems across the Japanese Archipelago, we explored hubs within "metacommunity-scale" networks of plant-fungus associations. In total, the metadata included 8080 fungal operational taxonomic units (OTUs) detected from 227 local populations of 150 plant species/taxa.

RESULTS

Few fungal OTUs were common across all the eight forests. However, in each of the metacommunity-scale networks representing northern four localities or southern four localities, diverse mycorrhizal, endophytic, and pathogenic fungi were classified as "metacommunity hubs," which were detected from diverse host plant taxa throughout a climatic region. Specifically, Mortierella (Mortierellales), Cladophialophora (Chaetothyriales), Ilyonectria (Hypocreales), Pezicula (Helotiales), and Cadophora (incertae sedis) had broad geographic and host ranges across the northern (cool-temperate) region, while Saitozyma/Cryptococcus (Tremellales/Trichosporonales) and Mortierella as well as some arbuscular mycorrhizal fungi were placed at the central positions of the metacommunity-scale network representing warm-temperate and subtropical forests in southern Japan.

CONCLUSIONS

The network theoretical framework presented in this study will help us explore prospective fungi and bacteria, which have high potentials for agricultural application to diverse plant species within each climatic region. As some of those fungal taxa with broad geographic and host ranges have been known to promote the survival and growth of host plants, further studies elucidating their functional roles are awaited.

Potential of Finger Millet Indigenous Rhizobacterium Pseudomonas sp. MSSRFD41 in Blast Disease Management-Growth Promotion and Compatibility With the Resident Rhizomicrobiome

Finger millet [Eleusine coracona (L). Gaertner] "Ragi" is a nutri-cereal with potential health benefits, and is utilized solely for human consumption in semi-arid regions of Asia and Africa. It is highly vulnerable to blast disease caused by Pyricularia grisea, resulting in 50-100% yield loss. Chemical fungicides are used for the management of blast disease, but with great safety concern. Alternatively, bioinoculants are widely used in promoting seedling efficiency, plant biomass, and disease control. Little is known about the impact of introduced indigenous beneficial rhizobacteria on the rhizosphere microbiota and growth promotion in finger millet. Strain MSSRFD41 exhibited a 22.35 mm zone of inhibition against P. grisea, produces antifungal metabolites, siderophores, hydrolytic enzymes, and IAA, and solubilizes phosphate. Environmental SEM analysis indicated the potential of MSSRFD41 to inhibit the growth of P. grisea by affecting cellular functions, which caused deformation in fungal hyphae. Bioprimed finger millet seeds exhibited significantly higher levels of germination, seedling vigor index, and enhanced shoot and root length compared to control seeds. Cross streaking and RAPD analysis showed that MSSRFD41 is compatible with different groups of rhizobacteria and survived in the rhizosphere. In addition, PLFA analysis revealed no significant difference in microbial biomass between the treated and control rhizosphere samples. Field trials showed that MSSRFD41 treatment significantly reduced blast infestation and enhanced plant growth compared to other treatments. A liquid formulated MSSRFD41 product maintained shelf life at an average of 10⁸ CFU ml^-1 over 150 days of storage at 25°C. Overall, results from this study demonstrated that Pseudomonas sp. MSSRFD41, an indigenous rhizobacterial strain, is an alternative, effective, and sustainable resource for the management of P. grisea infestation and growth promotion of finger millet.

Cultivable fungi present in Antarctic soils: taxonomy, phylogeny, diversity, and bioprospecting of antiparasitic and herbicidal metabolites

Molecular biology techniques were used to identify 218 fungi from soil samples collected from four islands of Antarctica. These consisted of 22 taxa of 15 different genera belonging to the Zygomycota, Ascomycota, and Basidiomycota. Mortierella, Antarctomyces, Pseudogymnoascus, and Penicillium were the most frequently isolated genera and Penicillium tardochrysogenum, Penicillium verrucosus, Goffeauzyma gilvescens, and Mortierella sp. 2 the most abundant taxa. All fungal isolates were cultivated using solid-state fermentation to obtain their crude extracts. Pseudogymnoascus destructans, Mortierella parvispora, and Penicillium chrysogenum displayed antiparasitic activities, whilst extracts of P. destructans, Mortierella amoeboidea, Mortierella sp. 3, and P. tardochrysogenum showed herbicidal activities. Reported as pathogenic for bats, different isolates of P. destructans exhibited trypanocidal activities and herbicidal activity, and may be a source of bioactive molecules to be considered for chemotherapy against neglected tropical diseases. The abundant presence of P. destructans in soils of the four islands gives evidence supporting that soils in the Antarctic Peninsula constitute a natural source of strains of this genus, including some P. destructans strains that are phylogenetically close to those that infect bats in North America and Europe/Palearctic Asia.

Banana Fusarium Wilt Disease Incidence Is Influenced by Shifts of Soil Microbial Communities Under Different Monoculture Spans

The continuous cropping of banana in the same field may result in a serious soil-borne Fusarium wilt disease and a severe yield decline, a phenomenon known as soil sickness. Although soil microorganisms play key roles in maintaining soil health, the alternations of soil microbial community and relationship between these changes and soil sickness under banana monoculture are still unclear. Bacterial and fungal communities in the soil samples collected from banana fields with different monoculture spans were profiled by sequencing of the 16S rRNA genes and internal transcribed spacer using the MiSeq platform to explore the relationship between banana monoculture and Fusarium wilt disease in the present study. The results showed that successive cropping of banana was significantly correlated with the Fusarium wilt disease incidence. Fungal communities responded more obviously and quickly to banana consecutive monoculture than bacterial community. Moreover, a higher fungal richness significantly correlated to a higher banana Fusarium wilt disease incidence but a lower yield. Banana fungal pathogenic genus of Fusarium and Phyllosticta were closely associated with banana yield depletion and disease aggravation. Potential biocontrol agents, such as Funneliformis, Mortierella, Flavobacterium, and Acidobacteria subgroups, exhibited a significant correlation to lower disease occurrence. Further networks analysis revealed that the number of functionally interrelated modules decreased, the composition shifted from bacteria- to fungi-dominated among these modules, and more resources-competitive interactions within networks were observed after banana long-term monoculture. Our results also showed that bacterial and fungal communities were mainly driven by soil organic matter. Overall, the findings indicated that the bacterial and fungal community structures altered significantly after banana long-term monoculture, and the fungal richness, abundance of Fusarium, interactions between and within bacteria and fungi in ecological networks, and soil organic matter were associated with banana soil-borne Fusarium wilt disease.

Mortiamides A-D, Cyclic Heptapeptides from a Novel Mortierella sp. Obtained from Frobisher Bay

Four new cyclic heptapeptides, mortiamides A-D (1-4), were obtained from a novel Mortierella sp. isolate obtained from marine sediment collected from the intertidal zone of Frobisher Bay, Nunavut, Canada. The structures of the compounds were elucidated by NMR spectroscopy and tandem mass spectrometry. The absolute configurations of the amino acids were determined using Marfey's method. Localization of l and d amino acids within each compound was ascertained by retention time comparison of the partial hydrosylate products of each compound to synthesized dipeptide standards using LC-HRMS. Compounds 1-4 did not exhibit any significant antimicrobial or cytotoxic activity.

Bifiguratus adelaidae, gen. et sp. nov., a new member of Mucoromycotina in endophytic and soil-dwelling habitats

Illumina amplicon sequencing of soil in a temperate pine forest in the southeastern United States detected an abundant, nitrogen (N)-responsive fungal genotype of unknown phylogenetic affiliation. Two isolates with ribosomal sequences consistent with that genotype were subsequently obtained. Examination of records in GenBank revealed that a genetically similar fungus had been isolated previously as an endophyte of moss in a pine forest in the southwestern United States. The three isolates were characterized using morphological, genomic, and multilocus molecular data (18S, internal transcribed spacer [ITS], and 28S rRNA sequences). Phylogenetic and maximum likelihood phylogenomic reconstructions revealed that the taxon represents a novel lineage in Mucoromycotina, only preceded by Calcarisporiella, the earliest diverging lineage in the subphylum. Sequences for the novel taxon are frequently detected in environmental sequencing studies, and it is currently part of UNITE's dynamic list of most wanted fungi. The fungus is dimorphic, grows best at room temperature, and is associated with a wide variety of bacteria. Here, a new monotypic genus, Bifiguratus, is proposed, typified by Bifiguratus adelaidae.

Biological Significance of Marine Actinobacteria of East Coast of Andhra Pradesh, India

An attempt was made to identify actinobacterial strains present in the marine soil of East Coast regions viz., Chirala, Bapatla, and Peddaganjam, Andhra Pradesh; Kanyakumari, Tamil Nadu and Goa, Goa along with the study of their antimicrobial potential. Eight out of 73 actinobacterial strains isolated from these regions showed strong antimicrobial activity against Gram positive bacteria, Gram negative bacteria, and Candida albicans. Molecular identification (16S rRNA analysis) of the eight strains revealed that they belong to Dietzia sp., Kocuria sp., Nocardiopsis sp., and Streptomyces spp. ISP (International Streptomyces project) -1, ISP-2 and starch casein media supported high antimicrobial potential after 5-6 days of growth. Production of antimicrobials by the strains varied significantly with different carbon and nitrogen sources. Gas chromatography mass spectrometry (GCMS) analysis of volatile compounds produced by the strains illustrated an array of antimicrobial compounds such as 1, 2-benzene dicarboxylic acid, 2-piperidinone, pyrrolo[1,2-a]pyrazine-1,4-dion, phenyl ethyl alcohol, 3-phenyl propionic acid etc. Ours is the first report on the study and detection of above mentioned antimicrobial metabolites from Dietzia sp. (A3), Kocuria sp. (A5), and Nocardiopsis sp. (A7). By sequence based analysis for secondary metabolites, non-ribosomal peptide synthetase (NRPS) gene cluster was noticed in six strains (A2, A3, A4, A6, A7, and A8) and none of them had polyketide synthase (PKS) system. The present study intimates the biological potentiality of the actinobacterial strains isolated from East Coast of Andhra Pradesh, India which reveals further scope to investigate new bioactive compounds from them by employing both natural product chemistry and modern biotechnological aspects.

Strain-specific variation in plant growth promoting volatile organic compounds production by five different Pseudomonas spp. as confirmed by response of Vigna radiata seedlings

AIM

Analysis of a blend of volatile organic compounds (VOCs) released by Pseudomonas spp. with growth-promoting effect in Vigna radiata seedlings.

METHODS AND RESULTS

Plant growth-promoting activity of VOCs produced by five different Pseudomonas spp. was investigated by I-plate technique. VOCs produced by different organisms were extracted by various solvents (methanol, ethyl acetate, hexane and butanol) and were identified by gas chromatography-mass spectrometric analysis. The major VOCs identified were undecane, nonadecane, hexacosane, tetradecane, heptacosane, pentadecane, dodecane and tetratetracontane. The cultural conditions for the production of VOCs with plant growth enhancement effect were optimized and further confirmed using pure pentadecane as a candidate VOC.

CONCLUSIONS

The study provides insight into plant beneficial effect of VOCs produced by Pseudomonas spp. Remarkable modulation in the production of VOCs with plant growth-promoting effect by rhizobacteria was found to be dependent on the bacterial strain and its concentration.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study describes the requirement to consider bacterial VOC production also for preparing plant probiotic formulations. As VOCs are least considered for preparation of commercial plant growth-promoting rhizobacterial strain formulation, the results of the study is highly significant.