The diversity of endophytic fungi in the above-ground tissue of two Lycopodium species in Poland

Endophytic Fungal Diversity of Mangrove Ferns Acrostichum speciosum and A. aureum in China

Microbial communities are an important component of mangrove ecosystems. In order to reveal the diversity of endophytic fungi in the mangrove ferns Acrostichum speciosum and A. aureum in China, the internal transcribed spacer (ITS) regions of endophytic fungi in four plant tissues (leaves, petioles, roots, and rhizomes) from three locations (Zhanjiang, Haikou, and Wenchang) were sequenced. The richness, species composition, and community similarity were analyzed. The main results are as follows: the dominant fungi in A. speciosum and A. aureum belonged to the phyla Ascomycota and Basidiomycota, accounting for more than 75% of the total identified fungi; in terms of species composition at the operational taxonomic unit (OTU) level, the endophytic fungi in A. aureum were more diverse than those in A. speciosum, and the endophytic fungi in rhizomes were more diverse than in other tissues. In Zhanjiang, both A. speciosum and A. aureum showed the richest diversity of endophytic fungi, both at the OTU classification level and in terms of species composition. Conversely, the richness of endophytic fungi in the samples of A. speciosum from Wenchang and Haikou is extremely low. The regional differences in dominant fungi increase with the degrading of taxonomic levels, and there were also significant differences in the number of unique fungi among different origins, with Zhanjiang samples having a larger number of unique fungi than the other locations. There were significant differences in the dominant fungi among different tissues, with Xylariales being the dominant fungi in rhizomes of A. speciosum and Hypocreales being the dominant fungi in the petioles, roots, and rhizomes of A. aureum. Overall, the community similarity of endophytic fungi among locations is moderately dissimilar (26-50%), while the similarity between tissues is moderately similar (51-75%). The low diversity of endophytic fungi could be one of the main reasons for the endangerment of A. speciosum. The protection of the diversity of endophytic fungi in the underground parts of A. speciosum is essential for the conservation of this critically endangered mangrove fern.

Bioactivity study and metabolic profiling of Colletotrichum alatae LCS1, an endophyte of club moss Lycopodium clavatum L

Endophytes are silent microbial partners of green plants that ensure hosts' survival in odd conditions. They are known as the factories of multipotent metabolites with diverse bioactivities beneficial to modern pharmaceuticals industry. Endophytic fungi have been screened from a variety of plants and it is the first-time endophytes of club moss is being studied for production of antibacterial and antioxidative compounds. The present study reveals that Lycopodium clavatum L. harbors a potent niche of bioactive endophytic fungi and Colletotrichum alatae LCS1 was the prime producer of antibacterial and antioxidative compounds among them. The minimum inhibitory and bactericidal concentrations of ethyl- acetate culture extract ranged from 15.62 to 250 μg/mL against four Gram negative and three Gram positive microorganisms including methicillin resistant Staphylococcus aureus (ATCC-33591). Bio-autogram based screening followed by Gas chromatographic analysis confirmed the occurrence of 17 bioactive compounds and α-bisabolol is known to be the prime one. Alfa bisabolol is a unique and versatile bioactive essential oil and facilitates variety of functions. Killing kinetics data along with leakage of macromolecules into extracellular environment supports the cidal activity of the antibacterial principles at MBC values. Isolate C. alatae LCS1 was optimized by one variable at a time system coupled with response surface methodology for broad spectrum antibacterial production. The organism yielded maximum response (22.66±0.894 mm of zone of inhibition against MRSA) in 250 mL Erlenmeyer flask containing 50 mL potato dextrose broth supplemented with (g/L) glucose, 7.53; yeast extract concentration, 0.47; NaCl, 0.10 with medium pH 6.46; after 134 hours of incubation at 26°C. Optimized fermentation parameters enhanced antibacterial activity up-to more than 50% than the pre-optimized one (10.33±0.57 mm). Endophytic LCS1 was also efficient in free radical scavenging tested by DPPH, ABTS, H2O2 and FRAP assay with an IC50 values of 23.38±5.32 to 82.873±6.479 μg/mL.

The assembly of wheat-associated fungal community differs across growth stages

Plant-associated fungal communities play a vital role in plant adaptations, physiological functions, and productivity. Therefore, it is important to reveal the mechanisms driving the assembly of these communities. Yet it is still not fully understood how community assembly and structure differentiate in plant compartments, growth seasons, and varieties at large geographic distances. In this study, we analyzed bulk soil and plant-associated fungal communities of five wheat varieties across two growth stages in three biogeographic sites with distances of about 324, 534, or 800 km apart between any two locations. Our results indicated that the fungal community varied primarily across the sample types (leaf endosphere, root endosphere, rhizosphere, and bulk soil), followed by growth stage. Compared with the regreening stage, lower α-diversity and more dominance by abundant species in the fungal community were observed in wheat-associated compartments (four sample types except for bulk soil) at the heading stage. Additionally, within each wheat-associated compartment across every growth stage, location had stronger effects on fungal community assembly than the wheat variety. The effects of variety on fungal community assembly were location specific as were the growth-stage patterns of varietal effects on leaf endosphere and rhizosphere fungal communities. We further detected a less diverse but abundant core fungal taxa that could be grouped into three clusters associated mainly with location. This study characterized the interplay effects between plant selection (compartment, growth stage, variety) and environment (location) on wheat-associated mycobiomes by determining drivers of fungal community assembly and core fungal taxa in field conditions. KEY POINTS: • Fungal community assembly was mainly shaped by sample type and growth stage • A lower diversity and more abundant core fungal taxa were shown at heading stage • Location had stronger effects on fungal community assembly than variety.

Organs, Cultivars, Soil, and Fruit Properties Affect Structure of Endophytic Mycobiota of Pinggu Peach Trees

Pinggu peach (Prunus persica (L.)) has great economic and ecological value in north China. As a plant, the peach is naturally colonized by a variety of endophytic fungi, which are very important for tree growth and health. However, the mycobiota composition and their affecting factors of the peach trees are still unknown. In our study, the fungal communities in flowers, leaves, stems, and roots of the three cultivars (Dajiubao, Qingfeng, and Jingyan) of Pinggu peach trees and in the rhizosphere soils were investigated by both Illumina Miseq sequencing of ITS rDNA and traditional culturing methods. For organs, except for roots, flowers had the highest fungal richness and diversity, while the leaves had the lowest richness and diversity. Ascomycota and Basidiomycota were the most abundant phyla among samples. The fungal assemblage composition of each organ was distinctive. Fungal communities of the three cultivars also differed from each other. The fungal community structure significantly correlated with soil pH, soil K, fruit soluble solid content, and fruit titratable acidity with the redundancy analysis (RDA). Most isolated fungal strains can be found within high-throughput sequencing identified taxa. This study indicates that plant organs, the cultivars, the soil, and fruit properties may have profound effects on the endophytic fungal community structure associated with Pinggu peach trees. With this study, microbiota-mediated pathogen protection and fruit quality promotion associated with peach trees could be further studied.

Endophytic Mycobiota of Jingbai Pear Trees in North China

Endophytic fungi exist in all known plants and play an important role for plant growth and health. As an important forest tree the Jingbai pear (the best quality cultivar of Pyrus ussuriensi Maxim. ex Rupr.) has great ecological as well as economic value in north China. However, the mycobiota of the pear tree is still unknown. In this study, the fungal communities in different organs of the tree and in rhizosphere soils were investigated by Illumina Miseq sequencing of ITS rDNA. For organs, the roots had the highest fungal richness and diversity, while the flowers had the lowest richness and diversity. The results demonstrated that each of the organs investigated harbored a distinctive fungal assemblage. Overall, Ascomycota was the most abundant phyla, followed by Basidiomycota and Zygomycota. Fungal communities from the different soils also differed from each other. The redundancy analysis (RDA) showed that fungal community structure correlated significantly with soil temperature, soil pH, soil nitrogen and soil carbon contents. The results indicate that plant organs, site conditions and soil properties may have important influences on the endophytic fungal community structure associated with Jingbai pear trees.

The root-symbiotic Rhizoscyphus ericae aggregate and Hyaloscypha (Leotiomycetes) are congeneric: Phylogenetic and experimental evidence

Data mining for a phylogenetic study including the prominent ericoid mycorrhizal fungus Rhizoscyphus ericae revealed nearly identical ITS sequences of the bryophilous Hyaloscypha hepaticicola suggesting they are conspecific. Additional genetic markers and a broader taxonomic sampling furthermore suggested that the sexual Hyaloscypha and the asexual Meliniomyces may be congeneric. In order to further elucidate these issues, type strains of all species traditionally treated as members of the Rhizoscyphus ericae aggregate (REA) and related taxa were subjected to phylogenetic analyses based on ITS, nrLSU, mtSSU, and rpb2 markers to produce comparable datasets while an in vitro re-synthesis experiment was conducted to examine the root-symbiotic potential of H. hepaticicola in the Ericaceae. Phylogenetic evidence demonstrates that sterile root-associated Meliniomyces, sexual Hyaloscypha and Rhizoscyphus, based on R. ericae, are indeed congeneric. To this monophylum also belongs the phialidic dematiaceous hyphomycetes Cadophora finlandica and Chloridium paucisporum. We provide a taxonomic revision of the REA; Meliniomyces and Rhizoscyphus are reduced to synonymy under Hyaloscypha. Pseudaegerita, typified by P. corticalis, an asexual morph of H. spiralis which is a core member of Hyaloscypha, is also transferred to the synonymy of the latter genus. Hyaloscypha melinii is introduced as a new root-symbiotic species from Central Europe. Cadophora finlandica and C. paucisporum are confirmed conspecific, and four new combinations in Hyaloscypha are proposed. Based on phylogenetic analyses, some sexually reproducing species can be attributed to their asexual counterparts for the first time whereas the majority is so far known only in the sexual or asexual state. Hyaloscypha bicolor sporulating in vitro is reported for the first time. Surprisingly, the mycological and mycorrhizal sides of the same coin have never been formally associated, mainly because the sexual and asexual morphs of these fungi have been studied in isolation by different research communities. Evaluating all these aspects allowed us to stabilize the taxonomy of a widespread and ecologically well-studied group of root-associated fungi and to link their various life-styles including saprobes, bryophilous fungi, root endophytes as well as fungi forming ericoid mycorrhizae and ectomycorrhizae.

Comparative Study of the Colonization of Chromolaena and Tobacco Plants by Bacteria safensis CS4 using Different Methods of Inoculation

BACKGROUND AND OBJECTIVES

This study entails the effectiveness of colonization of bacterial endophytes following inoculation of the cells in plants.

METHODOLOGY

Different methods of inoculation including seed immersion, root immersion and foliar spray were studied on Chromolaena odorata and Nicotiana tabacum for 10, 20 and 30 days. This was to ascertain the colonization ability of the endophytic strain amongst the two set of plants. The foliar parts of the plants were assessed post inoculation for the presence of the bacteria strain, followed by the growth parameters in the plant. Significant differences at p<0.05 of colonization were established by the different inoculation methods.

RESULTS

Foliar spray demonstrated the highest colonization in both Chromolaena and tobacco plants followed by root immersion. Leaf inoculation in tobacco plant demonstrated a positive colonization which is not significant. However, seed inoculation provided colonization in Chromolaena plant at 10, 20 and 30 days post inoculation at a frequency lower than that of tobacco. With root immersion in Chromolaena, there was colonization at 10 days post inoculation, no colonization at 20 days post inoculation, but colonization re-appeared at 30 days (PI). Growth index measured demonstrated a positive relationship between the inoculation of the endophyte and the growth parameters which included stem length and germination rate.

CONCLUSION

This study, therefore, showed that the bacteria strain B. safensis CS4 can effectively be horizontally transferred into tobacco and Chromolaena plants using different methods. Foliar spraying demonstrated the optimal colonization of the strain in the plant leaves.

Fungal Root Microbiome from Healthy and Brittle Leaf Diseased Date Palm Trees (Phoenix dactylifera L.) Reveals a Hidden Untapped Arsenal of Antibacterial and Broad Spectrum Antifungal Secondary Metabolites

In this study, we aimed to explore and compare the composition, metabolic diversity and antimicrobial potential of endophytic fungi colonizing internal tissues of healthy and brittle leaf diseased (BLD) date palm trees (Phoenix dactylifera L.) widely cultivated in arid zones of Tunisia. A total of 52 endophytic fungi were isolated from healthy and BLD roots of date palm trees, identified based on internal transcribed spacer-rDNA sequence analysis and shown to represent 13 species belonging to five genera. About 36.8% of isolates were shared between healthy and diseased root fungal microbiomes, whereas 18.4 and 44.7% of isolates were specific to healthy and BLD root fungal microbiomes, respectively. All isolates were able to produce at least two of the screened enzymes including amylase, cellulase, chitinase, pectinase, protease, laccase and lipase. A preliminary screening of the isolates using disk diffusion method for antibacterial activity against four Gram-positive and three Gram-negative bacteria and antifungal activities against three phytopathogenic fungi indicated that healthy and BLD root fungal microbiomes displayed interesting bioactivities against examined bacteria and broad spectrum bioactivity against fungal pathogens. Some of these endophytic fungi (17 isolates) were fermented and their extracts were evaluated for antimicrobial potential against bacterial and fungal isolates. Results revealed that fungal extracts exhibited antibacterial activities and were responsible for approximately half of antifungal activities against living fungi. These results suggest a strong link between fungal bioactivities and their secondary metabolite arsenal. EtOAc extracts of Geotrichum candidum and Thielaviopsis punctulata originating from BLD microbiome gave best results against Micrococcus luteus and Bacillus subtilis with minimum inhibitory concentration (MIC, 0.78 mg/mL) and minimum bactericidal concentration (6.25 mg/mL). G. candidum gave the best result against Rhizoctonia solani with MIC 0.78 mg/mL and minimum fungicidal concentration (MFC, 6.25 mg/mL). In conclusion, using plant microbiomes subjected to biotic stresses offers new endophytes with different bioactivities than those of healthy plants. Therefore, date palm endophytic fungi represent a hidden untapped arsenal of antibacterial and broad spectrum antifungal secondary metabolites and could be considered promising source of bioactive compounds with industrial and pharmaceutical applications.

Spatial and seasonal influences on culturable endophytic mycobiota associated with different tissues of Eugenia jambolana Lam. and their antibacterial activity against MDR strains

BACKGROUND

Present study focuses on diversity and distribution analysis of endophytic fungi associated with different tissues of Eugenia jambolana. The influence of season and geographical location on diversity and distribution of endophytic fungi has been analyzed. Antibacterial activity of isolated fungal species has also been investigated against MDR bacterial strains.

RESULT

A total of 1896 endophytic fungal isolates were obtained from healthy, surface sterilized tissues of leaf, stem and petiole tissues during summer, monsoon and winter season. Out of 24 fungal species isolated, 20 species belong to class Ascomycetes, 2 to Basidiomycetes and 2 to Zygomycetes. Maximum species diversity was in rainy season whereas colonization frequency was in winter. All the diversity indices showed maximum species diversity at site 5 (Yamunanager), rainy among the seasons and leaf among the tissues studied. Aspergillus genus was most frequently isolated. Aspergillus niger and Alternaria alternata were most dominant species. Three way ANOVA results showed that effect of season was highly significant on species diversity in relation to sites and tissues. 60% endophytic fungal extracts showed significant antibacterial activity against one or more than one MDR bacterial strain.

CONCLUSION

Different fungal species were recovered from different sites but the inter-site comparisons were not significant according to Jaccard similarity coefficient. Diversity of such fungal endophytes indicates that Eugenia jambolana plant acts as an ecosystem facilitating survival of many microbes with impressive antibacterial potential.