Biocontrol potential of Bacillus velezensis HG-8-2 against postharvest anthracnose on chili pepper caused by Colletotrichum scovillei.

Anthracnose caused by Colletotrichum scovillei is a significant disease of pepper, including in postharvest stage. Bacillus species represent a potential microbial resource for controlling postharvest plant diseases. Here, a strain HG-8-2 was obtained and identified as Bacillus velezensis through morphological, biochemical, physiological, and molecular analyses. The culture filtrate showed highly antifungal activity against C. scovillei both in vitro and on pepper fruit. Crude lipopeptide extracts, which had excellent stability, could effectively inhibit mycelial growth of C. scovillei with an EC50 value of 28.48 ± 1.45 µg mL-1 and inhibited conidial germination. Pretreatment with the extracts reduced the incidence and lesion size of postharvest anthracnose on pepper fruit. Analysis using propidium iodide staining, malondialdehyde content detection and scanning electron microscope observation suggested that the crude lipopeptide extracts harbored antifungal activity by damaging cell membranes and mycelial structures. The RNA-seq analysis conducted on C. scovillei samples treated with the extracts, as compared to untreated samples, revealed significant alterations in the expression of multiple genes involved in protein biosynthesis. Overall, these results demonstrated that B. velezensis HG-8-2 and its crude lipopeptide extracts exhibit highly antagonistic ability against C. scovillei, thereby offering an effective biological agent for the control of anthracnose in pepper fruit.

Antifungal Potential and Mechanism of Bacillus velezensis HeN-7 Isolated from Tobacco Leaves on Bipolaris sorokiniana.

Wheat leaf blight caused by Bipolaris sorokiniana is a widespread fungal disease that poses a serious risk to wheat. Biological control without causing environmental pollution is one of the safest and most effective method to control plant diseases. The antagonistic bacterial strain HeN-7 (identified as Bacillus velezensis) was isolated from tobacco leaves cultivated in Henan province, China. The results of different concentrations of cell-free supernatant (CFS) from HeN-7 culture against B. sorokiniana mycelia showed that 20% HeN-7 CFS (v/v) reached the maximum inhibition rate of 96%. In the potted plants control assay, B. velezensis HeN-7 CFS exhibited remarkable biocontrol activity on the wheat infected with B. sorokiniana, the best pot control efficacy was 65% at 20% CFS. The research on the mechanism of action demonstrated that HeN-7 CFS induced the membrane lipid peroxidation in B. sorokiniana, leading to the disruption of cell membrane integrity and resulting in the leakage of cell contents; in addition, the intracellular mitochondrial membrane potential in mycelium dissipated and reactive oxygen species accumulated, thereby inhibiting the growth of B. sorokiniana. These results indicate that B. velezensis HeN-7 is a promising candidate as a biological control agent against Bipolaris sorokiniana infection.

The antagonistic activity of Streptomyces spiroverticillatus (No. HS1) against of poplar canker pathogen Botryosphaeria dothidea.

BACKGROUND: Poplar canker caused by Botryosphaeria dothidea is one of the most severe plant disease of poplars worldwide. In our study, we aimed to investigate the modes of antagonism by fermentation broth supernatant (FBS) of Streptomyces spiroverticillatus HS1 against B. dothidea. RESULTS: In vitro, the strain and FBS of S. spiroverticillatus HS1 significantly inhibited mycelial growth and biomass accumulation, and also disrupted the mycelium morphology of B. dothidea. On the 3rd day after treatment, the inhibition rates of colony growth and dry weight were 80.72% and 52.53%, respectively. In addition, FBS treatment damaged the plasma membrane of B. dothidea based on increased electrical conductivity in the culture medium, and malondialdehyde content of B. dothidea mycelia. Notably, the analysis of key enzymes in glycolysis pathway showed that the activity of hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK), Ca2+Mg2+-ATPase were significantly increased after FBS treatment. But the glucose contents were significantly reduced, and pyruvate contents were significantly increased in B. dothidea after treatment with FBS. CONCLUSIONS: The inhibitory mechanism of S. spiroverticillatus HS1 against B. dothidea was a complex process, which was associated with multiple levels of mycelial growth, cell membrane structure, material and energy metabolism. The FBS of S. spiroverticillatus HS1 could provide an alternative approach to biological control strategies against B. dothidea.

The Influence of Polysaccharide Fractions of the Lion's Mane Medicinal Mushroom Hericium erinaceus (Agaricomycetes) on the Immunomodulatory and Antioxidant Activity of Neutrophils Exposed to Stress of Different Durations.

Polysaccharide fractions from the mycelium of the lion's mane medicinal mushroom Hericium erinaceus BP 16, cultivated on sterile grain substrates (barley, oats, wheat, rice, rye), were isolated and characterized. One percent solutions were prepared from the resulting fractions, mixed with blood, which was then subjected to cold stress at a temperature of 6°C for 3, 5 and 7 d. It has been shown that the fraction of H. erinaceus grown on rye is characterized by a high content of the protein fraction and arabinose monosaccharide and contributes to the preservation of higher phagocytic, bactericidal and antioxidant activity cells throughout the entire period of stress. Polysaccharide fractions of the fungus H. erinaceus, grown on various grain substrates, can serve as an immunomodulatory and antioxidant food additive and provide significant benefits in the daily life of people with stress and reduced immunity.

Optimization of Mycelial Growth Parameters in Lion's Mane Edible Medicinal Mushroom Hericium erinaceus (Agaricomycetes) by Supplementation of Growth Hormones.

The present study was carried out to optimize the strain and evaluate the effect of amendment of growth media with different hormone concentrations for enhancing mycelium growth of lion's mane mushroom Hericium erinaceus under in vitro conditions. Among the five strains of H. erinaceus, He-04 strain showed maximum average GR (GRavr) of 4.78 mm d-1. Five different media, potato dextrose agar (PDA), malt extract agar, sawdust extract agar, wheat straw extract agar, and rice straw extract agar, amended with four concentrations (10, 20, 30, and 40 ppm) of gibberellic acid, kinetin, and indole acetic acid, were evaluated for promotion of mycelial growth of H. erinaceus. PDA was observed to be the best media promoting the mycelial growth of H. erinaceus. The highest mycelial GRavr 8.47 mm d-1 was observed in PDA amended with indole acetic acid (10 ppm) followed by gibberellic acid and kinetin (30 ppm) decreasing mycelial GRav to 8.15 and 7.75mm d-1, respectively. Temperature of 25°C and pH 7.0 was found to be the best for mycelium growth of H. erinaceus.

Effect of temperature on in vitro germination and growth of Colletotrichum fioriniae, a new emerging pathogen of olive fruits.

Olive anthracnose induced by different Colletotrichum species causes dramatic losses of fruit yield and oil quality. The increasing incidence of Colletotrichum fioriniae (Colletotrichum acutatum species complex) as causal agent of olive anthracnose in Italy, is endorsing new studies on its biology, ecology, and environmental factors such as temperature. Five isolates from different sampling sites in Lazio region (Central Italy) were studied under controlled laboratory conditions aiming to better understand the differences of thermal development among the isolates and to lay the foundations of a future mathematical model able to describe the key aspects of the pathogen's life cycle. The mycelial growth rate and the conidial germination rate were assessed at seven different constant temperatures (5, 10, 15, 20, 25, 30, and 35°C) and fixed relative humidity (100% RH). The obtained dataset was analysed to estimate the parameters of mathematical functions that connect the mycelial growth rate and the spore germination with the environmental temperature. The parameters set provided as the result of this study constitute a key step forward in the biological knowledge of the species and the basis for future formulations of mathematical models that might be the core of decision support systems in an integrated pest management framework.

Plant-derived citronellol can significantly disrupt cell wall integrity maintenance of Colletotrichum camelliae.

Anthracnose, a fungal disease, commonly infects tea plants and severely impacts the yield and quality of tea. One method for controlling anthracnose is the application of citronellol, a plant extract that exhibits broad-spectrum antimicrobial activity. Herein, the physiological and biochemical mechanism by which citronellol controls anthracnose caused by Colletotrichum camelliae was investigated. Citronellol exhibited excellent antifungal activity based on direct and indirect mycelial growth inhibition assays, with EC50 values of 76.88 mg/L and 29.79 µL/L air, respectively. Citronellol also exhibited good control effects on C. camelliae in semi-isolated leaf experiments. Optical and scanning electron microscopy revealed that citronellol caused C. camelliae mycelia to thin, fracture, fold and deform. Transmission electron microscopy revealed that the mycelial cell walls collapsed inward and separated, and the organelles became blurred after treatment with citronellol. The sensitivity of C. camelliae to calcofluor white staining was significantly enhanced by citronellol, while PI staining showed minimal fluorescence, and the relative conductivity of mycelia were not significantly different. Under citronellol treatment, the expression levels of ß-1,3-glucanase, chitin synthase, and chitin deacetylase-related genes were significantly decreased, while the expression levels of chitinase genes were increased, leading to lower chitinase activity and increased ß-1,3-glucanase activity. Therefore, citronellol disrupted the cell wall integrity of C. camelliae and inhibited normal mycelial growth.

Transcriptome Analysis Reveals the Effect of Oyster Mushroom Spherical Virus Infection in Pleurotus ostreatus.

Oyster mushroom spherical virus (OMSV) is a mycovirus that inhibits mycelial growth, induces malformation symptoms, and decreases the yield of fruiting bodies in Pleurotus ostreatus. However, the pathogenic mechanism of OMSV infection in P. ostreatus is poorly understood. In this study, RNA sequencing (RNA-seq) was conducted, identifying 354 differentially expressed genes (DEGs) in the mycelium of P. ostreatus during OMSV infection. Verifying the RNA-seq data through quantitative real-time polymerase chain reaction on 15 DEGs confirmed the consistency of gene expression trends. Both Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses highlighted the pivotal role of primary metabolic pathways in OMSV infection. Additionally, significant changes were noted in the gene expression levels of carbohydrate-active enzymes (CAZymes), which are crucial for providing the carbohydrates needed for fungal growth, development, and reproduction by degrading renewable lignocellulose. The activities of carboxymethyl cellulase, laccase, and amylase decreased, whereas chitinase activity increased, suggesting a potential mechanism by which OMSV influenced mycelial growth through modulating CAZyme activities. Therefore, this study provided insights into the pathogenic mechanisms triggered by OMSV in P. ostreatus.

Antifungal Effect of Bauhinia variegata Lectin (BvL) on Bipolaris oryzae.

The search for less harmful, ecologically efficient, more specific, and natural alternatives for the control of pathogens is essential. Bauhinia variegata lectin (BvL) is a protein that has numerous biological activities, including antifungal. The present study examines the potential in vitro of B. variegata lectin against the fungus Bipolaris oryzae, responsible for agricultural losses in southern Brazil, due to damage to rice fields during seed germination. Bioassays to assess the inhibition potential of BvL were performed, including fungal growth, spore formation, and germination, in concentrations of 0, 25, 50, and 100 µg mL-1. Only the concentration of 100 µg mL-1 successfully inhibited mycelial growth and spore germination, while in spore formation, all treatments inhibited sporulation. In addition, fluorescence microscopy analysis demonstrated the ability of lectin to bind to the fungus and the lack of detection in the presence of lactose, suggesting its interaction with the fungal cell wall structures. This study highlights the potential of B. variegata seed lectin to control mycelial growth, sporulation, and germination of the phytopathogenic fungus B. oryzae, posing as a new biotechnological possibility for biological control.

Sensorimotor control of robots mediated by electrophysiological measurements of fungal mycelia.

Living tissues are still far from being used as practical components in biohybrid robots because of limitations in life span, sensitivity to environmental factors, and stringent culture procedures. Here, we introduce fungal mycelia as an easy-to-use and robust living component in biohybrid robots. We constructed two biohybrid robots that use the electrophysiological activity of living mycelia to control their artificial actuators. The mycelia sense their environment and issue action potential-like spiking voltages as control signals to the motors and valves of the robots that we designed and built. The paper highlights two key innovations: first, a vibration- and electromagnetic interference-shielded mycelium electrical interface that allows for stable, long-term electrophysiological bioelectric recordings during untethered, mobile operation; second, a control architecture for robots inspired by neural central pattern generators, incorporating rhythmic patterns of positive and negative spikes from the living mycelia. We used these signals to control a walking soft robot as well as a wheeled hard one. We also demonstrated the use of mycelia to respond to environmental cues by using ultraviolet light stimulation to augment the robots' gaits.

Transcriptome analysis of the medicinal mushroom Sanghuangporus vaninii in response to white light stress.

Light is a vital environmental factor that promotes the growth and development of edible fungi mycelium. Under white light, the mycelium color of Sanghuangporus vaninii shifts during its growth stages. To investigate the impact of visible light on mycelial morphogenesis, a comparative transcriptomic analysis was conducted. This analysis revealed the molecular processes that underpin mycelial growth and development in S. vaninii when cultured in both darkness and light conditions. From the analysis, 13,643 genes were aligned using Illumina raw reads. Of these, 596 genes exhibited significant expression changes under white light exposure. Specifically, 226 genes were upregulated and 370 downregulated, spanning 55 different metabolic pathways. We further classified differentially expressed genes (DEGs), these genes play roles in photomorphogenesis, signal transduction, carbohydrate metabolism, and melanin production, among other processes. Some are also implicated in cell cycle regulation and the differential expression of respiratory functions. The validation of the differentially expressed transcripts using qRT-PCR showed complete agreement with RNA-Seq data for 9 transcripts. Meanwhile, the light had an inhibitory effect on the bioactive components in S. vaninii. These findings offer valuable insights into the transcriptional shifts and molecular mechanisms driving the color change in S. vaninii under light exposure, providing a basis for further research into mechanisms of light-response regulation.

Extramatrical mycelial biomass is mediated by fine root mass and ectomycorrhizal fungal community composition across tree species.

In many ecosystems, a large fraction of gross primary production is invested in mycorrhiza. Ectomycorrhizal (ECM) mycelium is involved in regulating soil carbon and nutrient cycling. However, little is known about how mycelial biomass, production and turnover differ depending on ECM fungal community composition and associated tree species. We quantified fine root biomass and length using soil cores, and mycelial traits (biomass, production, and turnover) using mesh-bags and ergosterol analysis, and identified ECM exploration types by Illumina MiSeq sequencing of four ECM-dominated tree species (Picea asperata, Larix gmelinii, Quercus aquifolioides and Betula albosinensis) in subalpine forest. The ECM fungal community composition separated between needle-leaved and broadleaved species, and between evergreen and deciduous species. The ratio of mycelial to fine root biomass was similar across the species regardless of genus-scale community composition and the relative abundance of exploration types. Compared to the other species, Q. aquifolioides displayed higher fine root biomass and mycelial biomass and production, dominated by contact-short exploration type. Mycelial turnover rate tended to be lowest in P. asperata, dominated by medium-long exploration type. Much higher production of mycelium and only slightly higher turnover rate in Q. aquifolioides suggests that its steady-state mycelial biomass would be higher than of the other species. Moreover, compared to the two deciduous species, with similar production but somewhat lower turnover rate, the standing crop of mycelium in P. asperata may stabilize at a higher value. Our findings, that exploration type may affect production and turnover, highlight the importance of characterizing ECM fungal communities by exploration types when estimating the contribution of mycelium biomass to forest carbon sink and storage.

Enhanced mycelium biomass and polysaccharide production in genetically modified Pleurotus ostreatus using agricultural wastes.

Edible fungi, healthier for humans and sustainable for the planet, attract unprecedented attention. In the study, the genetically modified Pleurotus ostreatus overexpression phosphoglucomutase (PGM) was constructed. P. ostreatus overexpression PGM (Po::PGM) had 4.96-folds higher expression level of PGM. Po::PGM grew thicker mycelium and more mycelium branches. Additional Ca2+ can inhibit mycelium growth, and cyclic adenosine monophosphate completely inhibited their growth of Po::PGM. Secondly, Overexpression of PGM made P. ostreatus become more sensitive to cell wall disruptors, and caused 12.75 % reduction of ß-1, 3-glucan and 40.53 % increase of chitin in cell wall. In submerged fermentation, the mycelia biomass yield and endopolysaccharide (IPS) production of Po::PGM in basic PDB can reach 11.18 g/l and 2.55 g/l, increasing by 20.86 % and 28.79 %, respectively. Whereas exopolysaccharide (EPS) reduced by 3.28 %. After replacing potato and glucose in PDB by wheat bran, mycelia biomass and EPS production of Po::PGM were all improved. The additional lactose in wheat bran did not only furtherly enhance mycelia biomass yield of Po::PGM to 27.78 g/l by 199.03 %, but IPS production also increased by 277.99 % to 6.07 g/l. The results provided us key ideas and important research directions that at least manipulating the PGM gene could obtain high-efficient use of agricultural wastes producing more fungus-based foods.

Micro-electrode array recording of extracellular electrical potentials of liquid static surface fermented Hericium erinaceus.

Hericium erinaceus is a basidiomycetes fungus with previously uncharacterised extracellular electrophysiology. Here, we present results of recordings of the electrical potentials of fungal biofilms of this species using microelectrode arrays (MEAs). In particular, we focused on modelling the temporal and spatial progression of the low frequency (≤ 1 Hz) potentials. Culture media control studies showed that the electrical potential activity results from the growth and subsequent spiking behaviours of the mycelium extracellular matrices. An antifungal assay using nystatin suspension, 10,000 unit/mL in DPBS, provided evidence for the biological origin of electrical potentials due to targeting of the selective permeability of the cell membrane and subsequent cessation of electrical activity. Conversely, injection of L-glutamic acid increased the combined multi-channel mean firing rate from 0.04 Hz to 0.1 Hz. Analysis of bursting and spatial propagation of the extracellular signals are also presented.

Extraction, Purification, Structural Characterization, and Antitumor Effects of Water-Soluble Intracellular Polysaccharide (IPSW-1) from Phellinus igniarius Mycelia.

Phellinus igniarius is a commonly used Chinese medicine fungus, and its polysaccharide is a valuable bioactive with antioxidant, antiaging, antitumor activities, etc. However, their bioactivities are influenced by their structural and physicochemical properties. Hence, this research isolated and purified homogeneous water-soluble intracellular polysaccharide (IPSW-1) from P. igniarius mycelia. A coherent study of its structural characteristics, conformation, and antitumor mechanisms was evaluated. The results showed IPSW-1 has no triple helical conformation according to the Congo red test. Based on FT-IR, periodate oxidation, Smith degradation, methylation analysis, 1H and 13C NMR spectroscopy data, and IPSW-1 consisted of α-d-glucopyranose (Glcp). The backbone of IPSW-1 consisted primarily of repeating three (1 → 6)-linked α-d-Glcp and one (1 → 3,4)-linked α-d-Glcp, with one terminal α-d-Glcp as side chains of 3-O-connected to the main chain for every four residues. The IPSW-1 had an inhibitory influence on HepG2 cell proliferation and inhibited the migration and invasion ability by down-regulating the expression levels of MMP-7 and RhoA. Moreover, IPSW-1 could inhibit the lysis of autophagosomes to inhibit autophagy and regulate mitochondrial membrane potential and pro-apoptotic protein Bax, which causes the caspase cascade to promote apoptosis, thereby inhibiting the role of tumor cells. These findings show IPSW-1 holds potential as an innovative functional food.

Using pre-fermented sugar beet pulp as a growth medium to produce Pleurotus ostreatus mycelium for meat alternatives.

This study aimed to determine the compatibility of pre-fermented sugar beet pulp to support the growth of Pleurotus ostreatus mycelium in submerged fermentation. The goal was to create a meat alternative based on mycelial-fermented pulp. It was further explored whether pre-fermentation with lactic acid bacteria (LAB) on the pulp increased meat-like properties, such as aroma, springiness, and hardness, in the final product. Three strains were selected from a high throughput screening of 105 plant-derived LAB based on their acidification and metabolite production in the pulp. Two homofermentative strains (Lactococcus lactis) and one heterofermentative strain (Levilactobacillus brevis) were selected based on their low ethanol production, high lactic acid production, and overall acidification of the pulp. Mycelium of P. ostreatus was grown in submerged fermentations on the pre-fermented pulp, and the biomass was removed by centrifugation. The fungal strain consumed all available sugars and acids and released arabinose to the media. Volatiles were detected using GC-MS, and a large increase in concentrations of hexanal, 1-octen-3-ol, and 2-octenal was measured. Concentration of 1-octen-3-ol was lower in the pre-fermented samples vs. the non-pre-fermented. LC-MS amino acid analysis showed the presence of all essential amino acids on day 0 and 7 of fermentation. The highest concentration of amino acids was for glutamic acid/glutamine and aspartic acid/asparagine. A decrease in all amino acids after 7 days of fungal fermentation was measured for all fermentations. The decrease was more significant for pre-fermented samples. This was also confirmed through a total protein determination, except for samples pre-fermented with Lactococcus lactis strain NFICC142 which increased in total protein content after fungal fermentation. The protein digestibility increased after fungal fermentation, and the highest increase was seen for non-pre-fermented samples. The springiness of the fermented product indicated similarities to meat alternatives, while the hardness was much lower than other meat alternatives. The results indicate that dried sugar beet pulp can be used for submerged cultivation of P. ostreatus, but that pre-fermentation does not improve the physical or nutritional properties of the end product significantly, except for an increased protein content for NFICC142 pre-fermented media. This is the first known attempt to use LAB and P. ostreatus in mixed fermentation to produce fungal mycelium, as well as the first attempt at using SBP in a liquid fermentation for mycelial production of P. ostreatus.

Biochemical mechanism of chlorine dioxide fumigation in inhibiting Ceratocystis fimbriata and black rot in postharvest sweetpotato.

The inhibitory properties and underlying mechanism of chlorine dioxide (ClO2) fumigation on the pathogen Ceratocystis fimbriata (C. fimbriata) and resultant sweetpotato black rot were investigated in vitro and in vivo. Results revealed that the ClO2 fumigation effectively inhibited fungal growth and induced obvious morphological variation of C. fimbriata mycelia. Furthermore, the mycelial membrane suffered damage, as evidenced by a significant increase in malondialdehyde content and the leakage of protein and nucleic acid from mycelia cells, accompanied by a marked decrease in ergosterol content. Additionally, ClO2 fumigation caused spores cell membrane damage, a notable decrease in spore viability, and induced cell apoptosis as indicated by reductions in spore germination rate, two fluorescence staining observations, and flow cytometry analysis. Moreover, the decay diameter of sweetpotato black rot lesions decreased significantly after ClO2 fumigation, and the growth of C. fimbriata was also inhibited. These findings present a novel and effective technology for inhibiting the progression of sweetpotato black rot.

Curse or blessing: Growth- and laccase-modulating properties of polyphenols and their oxidized derivatives on Botrytis cinerea.

Infection of grapevines with the grey mold pathogen Botrytis cinerea results in severe problems for winemakers worldwide. Browning of wine is caused by the laccase-mediated oxidation of polyphenols. In the last decades, Botrytis management has become increasingly difficult due to the rising number of resistances and the genetic variety of Botrytis strains. During the search for sustainable fungicides, polyphenols showed great potential to inhibit fungal growth. The present study revealed two important aspects regarding the effects of grape-specific polyphenols and their polymerized oxidation products on Botrytis wild strains. On the one hand, laccase-mediated oxidized polyphenols, which resemble the products found in infected grapes, showed the same potential for inhibition of growth and laccase activity, but differed from their native forms. On the other hand, the impact of phenolic compounds on mycelial growth is not correlated to the effect on laccase activity. Instead, mycelial growth and relative specific laccase activity appear to be modulated independently. All phenolic compounds showed not only inhibitory but also inductive effects on fungal growth and/or laccase activity, an observation which is reported for the first time. The simultaneous inhibition of growth and laccase activity demonstrated may serve as a basis for the development of a natural botryticide. Yet, the results showed considerable differences between genetically distinguishable strains, impeding the use of a specific phenolic compound against the genetic variety of wild strains. The present findings might have important implications for future understanding of Botrytis cinerea infections and sustainable Botrytis management including the role of polyphenols.

X-ray fluorescence and XANES spectroscopy revealed diverse potassium chemistries and colocalization with phosphorus in the ectomycorrhizal fungus Paxillus ammoniavirescens.

Ectomycorrhizal (ECM) fungi play a major role in forest ecosystems and managed tree plantations. Particularly, they facilitate mineral weathering and nutrient transfer towards colonized roots. Among nutrients provided by these fungi, potassium (K) has been understudied compared to phosphorus (P) or nitrogen (N). The ECM fungus Paxillus ammoniavirescens is a generalist species that interacts with the root of many trees and can directly transfer K to them, including loblolly pine. However, the forms of K that ECM fungi can store is still unknown. Here, we used synchrotron potassium X-ray fluorescence (XRF) and K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy on P. ammoniavirescens growing in axenic conditions to investigate the K chemistries accumulating in the center and the edge of the mycelium. We observed that various K forms accumulated in different part of the mycelium, including K-nitrate (KNO3), K-C-O compounds (such as K-tartrate K2(C4H4O6) and K-oxalate (K2C2O4)), K-S and K-P compounds. Saprotrophic fungi have been shown to excrete carboxylic acids, which in turn play a role in soil mineral weathering. Our finding of several K counter-ions to carboxylic acids may suggest that, besides their direct transfer to colonized roots, K ions can also be involved in the production of compounds necessary for sourcing nutrients from their surrounding environment by ECM fungi. Additionally, this work reveals that XANES spectroscopy can be used to identify the various forms of K accumulating in biological systems.

Actinomycetospora aeridis sp. nov., Actinomycetospora flava sp. nov. and Actinomycetospora aurantiaca sp. nov., endophytic actinobacteria isolated from wild orchid (Aerides multiflora Roxb).

Three novel mycelium-forming actinobacteria, designated OC33-EN06T, OC33-EN07T, and OC33-EN08T, were isolated from wild orchid (Aerides multiflora Roxb), collected from a hill evergreen forest in Northern Thailand. Strains OC33-EN06T and OC33-EN07T showed the highest 16S rRNA gene similarity with Actinomycetospora lutea TT00-04T, 99.17 and 99.45%, respectively. Strain OC33-EN08T showed high similarity with four species, namely 'Actinomycetospora termitidis Odt1-22T' (99.37%), Actinomycetospora chiangmaiensis DSM 45062T (99.02%), Actinomycetospora corticicola 014-5T (99.02%), and Actinomycetospora soli SF1T (98.81%). Comparative genome analysis of OC33-EN06T, OC33-EN07T, and OC33-EN08T with the closely related type strains showed that average nucleotide identity (ANI) based on blast, ANI based on MUMmer, and average amino acid identity values were less than 95% and the digital DNA-DNA hybridization values were less than 70%, all below the thresholds for species demarcation. The digital G+C content of OC33-EN06T, OC33-EN07T, and OC33-EN08T were 74.5, 74, and 74 mol%, respectively. These three strains developed bud-like chains of non-motile cylindrical spores with a smooth surface. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The whole-cell sugars contained ribose, arabinose, and galactose. The predominant menaquinone was MK-8(H4). The phospholipid profile included phosphatidylcholine, phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylinositol. Based on comparative analysis of genotypic, phenotypic and chemotaxonomic data, strains OC33-EN06T (=TBRC 18349T=NBRC 116543T), OC33-EN07T (=TBRC 18350T=NBRC 116544T), and OC33-EN08T (=TBRC 18318T=NBRC 116542T) represent the type strains of three novel species of the genus Actinomycetospora for which the names Actinomycetospora aeridis sp. nov., Actinomycetospora flava sp. nov., and Actinomycetospora aurantiaca sp. nov., are proposed.