Paenibacillus thermotolerans sp. nov., isolated from a hot spring in Yunnan Province, south-west China.

Two Gram-positive, rod-shaped, endospore-forming strains, YIM B05601 and YIM B05602T, were isolated from soil sampled at Hamazui hot spring, Tengchong City, Yunnan Province, PR China. Phylogenetic analysis based on 16S rRNA gene sequences suggested that the two strains fell within the genus Paenibacillus, appearing most closely related to Paenibacillus alkalitolerans YIM B00362T (96.9 % sequence similarity). Genome-based phylogenetic analysis confirmed that strains YIM B05601 and YIM B05602T formed a distinct phylogenetic cluster within the genus Paenibacillus. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of strains YIM B05601 and YIM B05602T with the related species P. alkalitolerans YIM B00362T were within the ranges of 74.43-74.57 % and 12.1-18.5 %, respectively, which clearly indicated that strains YIM B05601, YIM B05602T represented a novel species. Strains YIM B05601 and YIM B05602T exhibited 99.6 % 16S rRNA gene sequence similarity. The ANI and dDDH values between the two strains were 99.8 and 100 %, respectively, suggesting that they belong to the same species. Optimum growth for both strains occurred at pH 7.0 and 45 °C. The diagnostic diamino acid in the cell-wall peptidoglycan of strains YIM B05601 and YIM B05602T was meso-diaminopimelic acid. MK-7 was the predominant menaquinone. The polar lipids of strain YIM B05602T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, four unidentified glycolipids, an unidentified polarlipid and phosphatidylinositol mannoside. The major fatty acids of the two stains were iso-C15 : 0 and anteiso-C15 : 0. Based on phylogenomic and phylogenetic analyses coupled with phenotypic and chemotaxonomic characterizations, strains YIM B05601 and YIM B05602T could be classified as a novel species of the genus Paenibacillus, for which the name Paenibacillus thermotolerans sp. nov. is proposed. The type strain is YIM B05602T (=CGMCC 1.60051T=KCTC 43460T=NBRC 115924T).

Description and genomic characterization of Cohnella caldifontis sp. nov., isolated from hot springs in Yunnan province, south-west China.

A bacterial strain, Gram staining positive, strictly aerobic, rod-shaped, motile bacterium with flagellum and endospore-forming, designated strain YIM B05605T, was isolated from soil sampled in Hamazui hot springs, Tengchong City, Yunnan province, China. Optimum growth for the strain occurred at pH 7.0 and 45 °C. MK-7 was the main menaquinone in the strain YIM B05605T. The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. Diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylmonomethylethanolamine (PME), unidentified glycolipid (GL), three unknown aminophospholipids (APLs) and unidentified polarlipid (PL) were part of the polar lipid profile. The major fatty acids were anteiso-C15:0 and iso-C16:0. The DNA G + C content of the type strain was 58.76%. Genome-based phylogenetic analysis confirmed that strain YIM B05605T formed a distinct phylogenetic cluster within the genus Cohnella. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of strain YIM B05605T with the most related species C. fontinalis YT-1101T were 73.42% and 15.7%. Functional analysis by NR, Swiss-prot, Pfam, eggNOG, GO, KEGG databases revealed that strain YIM B05605T has 13 genes related to the sulfur cycle, 2 genes related to the nitrogen cycle. Based on phylogenomic and phylogenetic analyses coupled with phenotypic and chemotaxonomic characterizations, strain YIM B05605T could be classified as a novel species of the genus Cohnella, for which the name Cohnella caldifontis sp. nov., is proposed. The type strain is YIM B05605T (= CGMCC 1.60052T = KCTC 43462T = NBRC 115921T).

Paenibacillus hamazuiensis sp. nov., a bacterium isolated from Hamazui hot spring in Yunnan province, south-west China.

A bacterial strain, Gram-positive, aerobic, rod-shaped, motile, designated YIM B00624T which was isolated from a Hamazui hot spring in Tengchong, Yunnan province, south-west China. The strain grew well on International Streptomyces Project (ISP) 2 medium and colonies were creamy yellow, flat and circular. The results of 16S rRNA gene sequence similarity analysis showed that strain YIM B00624T was closely related to the type strain of Paenibacillus filicis S4T (95.9%). The main menaquinone of strain YIM B00624T was menaquinone-7 (MK-7) and major fatty acids were anteiso-C15:0, anteiso-C17:0 and C16:0. The isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine and four unidentified glycolipids. The DNA G+C content of strain YIM B00624T was 53.4 mol%. Based on physiological, phenotypic and chemotaxonomic data, strain YIM B00624T belongs to a novel species of the genus Paenibacillus, for which the name Paenibacillus hamazuiensis sp. nov. is proposed. The type strain is YIM B00624T (= CGMCC 1.19245T = KCTC 43365T).

Myrothins A-F from Endophytic Fungus Myrothecium sp. BS-31 Harbored in Panax notoginseng.

Endophytic fungi play important roles for host's stress tolerance including invasion by pathogenic microbes. Small molecules are common weapons in the microbe-microbe interactions. Panax notoginseng is a widely used traditional Chinese medicinal plant and harbors many endophytes, some exert functions against pathogens. Here, we report six new compounds named myrothins A-F (1-6) produced by Myrothecium sp. BS-31, an endophyte isolated from P. notoginseng, and their antifungal activities against pathogenic fungi causing host root-rot disease. Their structures were elucidated with analysis of spectroscopic data including 1D and 2D NMR, HR-ESI-MS. Myrothins B (2) and E (5) showed the weak activity against Fusarium oxysporum and Phoma herbarum, and myrothins F (6) showed weak activity against F. oxysporum.

Nocardia panacis sp. nov., a novel actinomycete with antiphytopathogen activity isolated from the rhizosphere of Panax notoginseng.

Strain YIM PH21724T was isolated from the rhizosphere of Panax notoginseng. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain exhibits close phylogenetic relatedness to Nocardia kroppenstedtii N1286T (97.70%), Nocardia farcinica NCTC 11134T (97.67%) and Nocardia puris DSM 44599T (97.40%). The menaquinones were identified as MK-9 (H4), MK-8 (H4, ω-cyclo) and MK-8 (H4), and the major fatty acids (> 10%) were identified as C16:0, C18:1 ω9c and C18:0 10-methyl. The polar lipids were found to be composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannosides and an unidentified lipid. The G + C content of the genomic DNA was determined to be 67.01 mol%. The phenotypic, chemotaxonomic, phylogenetic and genomic results clearly show strain YIM PH21724T should be classified in the genus Nocardia and represents a novel species, for which the name Nocardia panacis sp. nov. is proposed. The type strain is YIM PH21724T (= DSM 105904T = KCTC 49030T = CCTCC AA 2017043T).

Disruption of the pleiotropic gene scoC causes transcriptomic and phenotypical changes in Bacillus pumilus BA06.

BACKGROUND: Bacillus pumilus is a Gram-positive and endospore-forming bacterium broadly existing in a variety of environmental niches. Because it produces and secrets many industrially useful enzymes, a lot of studies have been done to understand the underlying mechanisms. Among them, scoC was originally identified as a pleiotropic transcription factor negatively regulating protease production and sporulation in B. subtilis. Nevertheless, its role in B. pumilus largely remains unknown. RESULTS: In this study we successfully disrupted scoC gene in B. pumilus BA06 and found increased total extracellular protease activity in scoC mutant strain. Surprisingly, we also found that scoC disruption reduced cell motility possibly by affecting flagella formation. To better understand the underlying mechanism, we performed transcriptome analysis with RNA sequencing. The result showed that more than one thousand genes were alternated at transcriptional level across multiple growth phases, and among them the largest number of differentially expressed genes (DEGs) were identified at the transition time point (12 h) between the exponential growth and the stationary growth phases. In accordance with the altered phenotype, many protease genes especially the aprE gene encoding alkaline protease were transcriptionally regulated. In contrast to the finding in B. subtilis, the aprN gene encoding neutral protease was transcriptionally downregulated in B. pumilus, implicating that scoC plays strain-specific roles. CONCLUSIONS: The pleiotropic transcription factor ScoC plays multiple roles in various cellular processes in B. pumilus, some of which were previously reported in B. subtilis. The supervising finding is the identification of ScoC as a positive regulator for flagella formation and bacterial motility. Our transcriptome data may provide hints to understand the underlying mechanism.

Amycolatopsis panacis sp. nov., isolated from Panax notoginseng rhizospheric soil.

A novel Gram-positive bacterium, designated strain YIM PH21725T, was isolated from a sample of rhizospheric soil of Panaxnotoginseng cultivated in Anning, Yunnan. The strain contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The main fatty acids identified were C17 : 0, iso-C15 : 0, iso-C16 : 0 and C16 : 0. The main menaquinone was MK-9 (H4). The polar lipids included phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol mannoside, phosphatidylinositol, phospholipids and phospholipids of an unidentified structure containing glucosamine. The G+C content of genomic DNA was 69.43 mol%. On the basis of its 16S rRNA gene sequence, strain YIM PH21725T should belong to the genus Amycolatopsis, and was closely related to Amycolatopsis sulphurea DSM 46092T (98.57 %), Amycolatopsis jejuensis JCM13280T (97.27 %), Amycolatopsis jiangsuensis KCTC 19885T (96.88 %) and Amycolatopsis ultiminotia JCM 16989T (96.8 %). The phenotypic, chemotaxonomic, phylogenetic and digital DNA-DNA hybridization results clearly indicated that strain YIM PH21725T represents a novel species of the genus Amycolatopsis, for which the name Amycolatopsispanacis sp. nov. is proposed. The type strain is YIM PH21725T (=CCTCC AA 2017044T=KCTC 49031T=DSM 105902T).

Novel Isochroman Dimers from Stachybotrys sp. PH30583: Fermentation, Isolation, Structural Elucidation and Biological Activities.

The rare anishidiol and five new isochromans, including three novel dimers with unprecedented skeletons, were isolated from Stachybotrys sp. PH30583. Their structures were determined by spectral analyses. The bioactivities of these compounds were also investigated. The dimers (6-10) inhibited acetylcholinesterase at 50 µM, but the monomers did not. To investigate the biogenesis of the novel dimers, a time-course investigation of metabolite production was undertaken.

Koningiopisins A-H, Polyketides with Synergistic Antifungal Activities from the Endophytic Fungus Trichoderma koningiopsis.

Eight new fungal polyketides named koningiopisins A-H (1-8) and four previously known polyketides (9-12) were isolated from the endophytic fungus Trichoderma koningiopsis YIM PH 30002. Their structures were elucidated using extensive spectral data interpretation, and their antifungal and synergistic activities were also evaluated. Koningiopisin C (3) exhibited in vitro antifungal activity against the phytopathogenic fungus Plectosphaerella cucumerina with an MIC of 16 µg/mL. Although the antifungal activities of single compounds were not obvious, a mixture of six compounds (4-9) exhibited potent synergistic antifungal activity against P. cucumerina with an MIC of 16 µg/mL, and the antifungal activity of the mixture of any two compounds with a 1:1 ratio was better than that observed from the individual compound. The synergistic biological activity of the metabolites in YIM PH 30002 demonstrates the significant ecological function of the endophyte for its host plant, and provides additional insight into the search for and development of agents for biological control.

Stackebrandtia endophytica sp. nov., an actinobacterium isolated from Tripterygium wilfordii.

A novel endophytic actinobacterium, designated strain YIM 64602T, was isolated from healthy stems of Tripterygium wilfordii. It grew at 15-40 °C, pH 6.0-9.0 and in the presence of 0-3 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain YIM 64602T belongs to the genus Stackebrandtia. Whole-cell hydrolysates of strain YIM 64602T contained the amino acid meso-diaminopimelic acid with the sugars mannose, rhamnose and glucose, and a trace of ribose. The major polar lipids were diphosphatidylglycerol, phosphatidylmethylethanolamine and phosphatidylethanolamine. MK-10(H6), MK-10(H4) and MK-11(H4) were the predominant components in the quinone system. The fatty-acid pattern was mainly composed of the saturated branched-chain acids iso-C16 : 0, anteiso-C17 : 0, iso-C15 : 0 and iso-C17 : 0. The DNA G+C content was 72.4 mol%. 16S rRNA gene sequence analysis showed the highest pairwise sequence identity (96.0-98.5 %) with the members of the genus Stackebrandtia. Strain YIM 64602T displayed a DNA-DNA relatedness of 43.9±0.4 % with the type strain Stackebrandtia albiflava YIM 45751T. Based on evidence from this polyphasic study, strain YIM 64602T ( = BCRC 16954T = DSM 45928T) is considered to represent a novel species of the genus Stackebrandtia, for which the name Stackebrandtia endophytica is proposed.

Triterpenoid and trichothecenes from a rhizospheric soil-derived Paramyrothecium sp. KMU22107.

A new phthalide derivative named paramlyktone (1) and a new arborinane-type triterpenoid named paramyrpenoid (2), together with ten previously described trichothecenes derivatives (3-12) were isolated and identified from a rhizospheric soil-derived Paramyrothecium sp. KMU22107 associated with Delphinium yunnanense. Their structural elucidation was achieved by the comprehensive analysis of spectroscopic data and comparison with literature values. Notably, paramyrpenoid (2) was the first example of an arborinane-type triterpenoid with a double bond at Δ12(13) and an additional methyl motif at C-8. This was the first report of arborinane-type triterpenoids from a fungus belonging to Paramyrothecium genus. In pharmacological studies, paramyrpenoid (2) demonstrated significant cytotoxic activity against the HL-60, SW480, A-549, MDA-MB-231 and SMMC-7721 cell lines, with IC50 values from 2.0 to 16.1 µM. Compounds 1 and 2 were also evaluated for anti-inflammatory, anti-acetylcholinesterase (AChE), and protein tyrosine phosphatase 1B (PTP1B) inhibitory activities in vitro.

Two new steroids from an endophytic fungus Phomopsis sp.

Two new steroids, (14ß,22E)-9,14-dihydroxyergosta-4,7,22-triene-3,6-dione (1) and (5α,6ß,15ß,22E)-6-ethoxy-5,15-dihydroxyergosta-7,22-dien-3-one (2), together with three known steroids, calvasterols A and B (3 and 4, resp.), and ganodermaside D (5), were isolated from the culture broth of an endophytic fungus Phomopsis sp. isolated from Aconitum carmichaeli. The structures of these compounds were elucidated on the basis of spectroscopic analysis, and their inhibitory activities against six pathogenic fungi were evaluated. Most of the compounds showed moderate or weak antifungal activities in a broth-microdilution assay.

RGO/Manganese Silicate/MOF-derived carbon Double-Sandwich-Like structure as the cathode material for aqueous rechargeable Zn-ion batteries.

Aqueous rechargeable Zn-ion batteries (ARZIBs) have been attracting a great deal of attention due to their immense potential in large-scale power grid applications. It is of great significance to explore cathode material with novel designed structure and first-class performances for ARZIBs. Herein, we successfully construct a double-sandwich-like structure, MOF-derived carbon/manganese silicate/reduced graphene oxide/manganese silicate/MOF-derived carbon (denoted as rGO/MnSi/MOF-C), as the cathode material for ARZIBs. Among the double-sandwich-like structure, manganese silicate (Mn2SiO4, denoted as MnSi) is in the middle of internal reduced graphene oxide (rGO) and external MOF-8 derived carbon (MOF-C). This integrated rGO/MnSi/MOF-C with double-sandwich-like structure can not only avert the sluggish electronic conduction progress caused by the conventional three-phase mixture system of rGO, MnSi and MOF-C, but also display promising Zn2+ storing capability. As expected, in mild aqueous 2 M (mol L-1) ZnSO4 + 0.2 M MnSO4 electrolyte, the initial discharge capacity of rGO/MnSi/MOF-C cathode reaches to 246 mAh·g-1, and the peak discharge capacity reaches to 462 mAh·g-1 at 0.1 A·g-1. This work not only involves the novel MnSi-based cathode for ARZIBs, but also first demonstrates our assumption of constructing the double-sandwich-like structure to improve Zn2+ storage. Moreover, the concept "double-sandwich-like structure" provides an idea for synthesizing the integrated carbon/transition metal silicates (TMSs)/carbon structure to boost the electrochemical properties of TMSs for energy-storing devices.

Sesquiterpenoids from the endophytic fungus Trichoderma sp. PR-35 of Paeonia delavayi.

A new bisabolane-type sesquiterpene, trichoderic acid (1), and a new acorane-type sesquiterpene, 2ß-hydroxytrichoacorenol (2), along with three known compounds, cyclonerodiol (3), cyclonerodiol oxide (4), and sorbicillin (5), were isolated from the culture broth of Trichoderma sp. PR-35, an endophytic fungus isolated from Paeonia delavayi. Their structures were elucidated on the basis of their IR, MS, and 1D- and 2D-NMR analyses. The antibacterial and antifungal activities of 1-5 towards various types of bacteria and fungi were tested. Most of the compounds showed moderate or weak antimicrobial activities in an agar-diffusion assay.

Impact of rhizosphere microorganisms on arsenic (As) transformation and accumulation in a traditional Chinese medical plant.

Panax notoginseng is an important traditional medicinal plant, but the commercial value is threatened by root-rot disease caused by rhizosphere microbes and a potential health risk caused by plant arsenic (As) accumulation. Whether rhizospheric microbes isolated from P. notoginseng rhizosphere soil could impact As uptake and transport into P. notoginseng is not yet known. Among the three root-rot disease-causing pathogens Fusarium flocciferum (PG 1), Fusarium oxysporum (PG 2), and Fusarium solani (PG 3) and one root-rot disease biocontrol fungus Trichoderma koningiopsis (FC 1) and five biocontrol-exerting bacterial species Bacillus siamensis (BC 1), Delftia acidovorans (BC 2), Brevibacillus formosus (BC 3), Mortierella alpine (BC 4), and Bacillus subtilis (BC 5), one As-resistant pathogen and four biocontrol microorganisms with As-resistant ability were identified. The As-transforming ability of the identified fungi and bacteria was ranked in the order of FC 1 > PG 1 and BC 2 > BC 3 > BC 1, respectively. Then, the As-resistant biocontrol and pathogenic microbes were initiated to colonize the rhizosphere of 1-year-old P. notoginseng seedlings growing in artificially As(V)-contaminated soil to evaluate the impact of microbe inoculation on P. notoginseng As uptake and transport capacity. Concentration of As in P. notoginseng tissues decreased in the order of the sequence stem > root > leaf. Compared to treatment without colonization by microorganism, inoculation with microorganisms increased As root uptake efficiency and root As concentration, especially under treatment of inoculation by BC 2 and PG 1 + BC 2. As transport efficiency from root to stem decreased by inoculation with microorganism, especially under treatment with inoculation of BC 2 and PG 1 + BC 2. However, the impact of microorganism colonization on As stem to leaf transport efficiency was not obvious. In summary, inoculation with rhizosphere microbes may increase As accumulation in P. notoginseng root, especially when using bacteria with high As transformation ability. Therefore, it is necessary to evaluate the As transformation capacity before applying biological control microorganism to the rhizosphere of P. notoginseng.

Construction of a High-Expression System in Bacillus through Transcriptomic Profiling and Promoter Engineering.

Bacillus subtilis is an ideal host for secretion and expression of foreign proteins. The promoter is one of the most important elements to facilitate the high-level production of recombinant protein. To expand the repertoire of strong promoters for biotechnological applications in Bacillus species, 14 highly transcribed genes based on transcriptome profiling of B. pumilus BA06 were selected and evaluated for their promoter strength in B. subtilis. Consequently, a strong promoter P2069 was obtained, which could drive the genes encoding alkaline protease (aprE) and green fluorescent protein (GFP) to express more efficiency by an increase of 3.65-fold and 18.40-fold in comparison with the control promoter (PaprE), respectively. Further, promoter engineering was applied to P2069, leading to a mutation promoter (P2069M) that could increase GFP expression by 3.67-fold over the wild-type promoter (P2069). Moreover, the IPTG-inducible expression systems were constructed using the lac operon based on the strong promoters of P2069 and P2069M, which could work well both in B. subtilis and B. pumilus. In this study, highly efficient expression system for Bacillus was constructed based on transcriptome data and promoter engineering, which provide not only a new option for recombinant expression in B. subtilis, but also novel genetic tool for B. pumilus.

Isolation and Characterization of New Phenazine Metabolites with Antifungal Activity against Root-Rot Pathogens of Panax notoginseng from Streptomyces.

Three new phenazine metabolites, strepphenazine A-C (1-3), along with a known compound baraphenazine E 4 were isolated from the culture broth of a Streptomyces strain YIM PH20095. The structures were elucidated based on the spectral data. Compounds 1-4 showed different antifungal activity against Fusarium oxysporum, Plectosphaerella cucumerina, Alternaria panax, and Phoma herbarum, which caused root-rot disease of Panax notoginseng with minimal inhibitory concentrations (MICs) of 16-64 µg/mL; compared with compound 4, compounds 1-3 showed better antifungal activity against some of these pathogenic fungi with MICs of 16-32 µg/mL, while compound 4 showed antifungal activity against F. oxysporum, P. cucumerina, and A. panax with the same MICs of 64 µg/mL. Thus, strain YIM PH20095 provides new sources for the development of biological control agents to prevent the infection of pathogenic fungi of P. notoginseng.

The streptazolin- and obscurolide-type metabolites from soil-derived Streptomyces alboniger YIM20533 and the mechanism of influence of γ-butyrolactone on the growth of Streptomyces by their non-enzymatic reaction biosynthesis.

Eleven new compounds with streptazolin- and obscurolide-type skeletons were isolated from soil-derived Streptomyces alboniger obtained from Tibet, China. Two types of unprecedented skeletons of obscurolide dimer and an obscurolide-type compound with an aromatic polyketide of pentanone substituted at the benzene ring were determined by spectral data analysis. Compound 11 was the first evidence of two nitrogens in streptazolin-type structures. Compound 1 indicated an inhibitory effect on nitric oxide production in LPS-activated macrophages with an inhibition ratio of 51.7% at 50 µM, and on anticoagulant activity on platelet activating factor (PAF)-induced platelet aggregation with an inhibition ratio of 26.0 ± 9.1% at 200 µg mL-1. 11 had anti-acetylcholinesterase activity with an inhibition ratio of 27.2% at a concentration of 50 µM. Mechanistic aspects of the non-enzymatic reaction as well as a more detailed picture of the biosynthetic relationships of the streptazolin- and obscurolide-type metabolites are described. Acidic and basic conditions can inhibit the growth of Streptomyces, and γ-butyrolactones were found to be hormones controlling antibiotic production in Streptomyces. In the pH fermentation tests, acylation of γ-butyrolactones was successfully used to explain the mechanism of influence on the growth of Streptomyces.

Lovastatin analogues and other metabolites from soil-derived Aspergillus terreus YIM PH30711.

Eight previously undescribed metabolites including of lovastatin analogues, a pair of diastereoisomers, a cyclopentenone dimer, and three polyketides were isolated from the culture of Aspergillus terreus YIM PH30711. Two types of unprecedented skeletons, benzene-cyclopentanone complex and linear polyketide, and an unusual dimer structure were determined by spectral analysis. Compound, 3α-hydroxy-3,5-dihydromonacolin L showed moderate activity against HMG-CoA reductase, with an inhibition ratio of 34% at the concentration of 50 µM, while lovastatin and dihydromonacolin K ethyl ester presented much stronger activity against HMGR with inhibition rates of 85% and 90% at the concentration of 50 µM, respectively. Aspereusin A was active against AChE with a ratio of 62% at the concentration of 50 µM, while its stereomers did not showed obvious inhibition (<10%). The configuration at C-4 of these three diastereoisomers was crucial in the inhibition against AChE, and the ß-orientation of substituted methoxyl acrylic acid should be beneficial to the combining with AChE.

Endophytic fungi harbored in Panax notoginseng: diversity and potential as biological control agents against host plant pathogens of root-rot disease.

BACKGROUND: Endophytic fungi play an important role in balancing the ecosystem and boosting host growth. In the present study, we investigated the endophytic fungal diversity of healthy Panax notoginseng and evaluated its potential antimicrobial activity against five major phytopathogens causing root-rot of P. notoginseng. METHODS: A culture-dependent technique, combining morphological and molecular methods, was used to analyze endophytic fungal diversity. A double-layer agar technique was used to challenge the phytopathogens of P. notoginseng. RESULTS: A total of 89 fungi were obtained from the roots, stems, leaves, and seeds of P. notoginseng, and 41 isolates representing different morphotypes were selected for taxonomic characterization. The fungal isolates belonged to Ascomycota (96.6%) and Zygomycota (3.4%). All isolates were classified to 23 genera and an unknown taxon belonging to Sordariomycetes. The number of isolates obtained from different tissues ranged from 12 to 42 for leaves and roots, respectively. The selected endophytic fungal isolates were challenged by the root-rot pathogens Alternaria panax, Fusarium oxysporum, Fusarium solani, Phoma herbarum, and Mycocentrospora acerina. Twenty-six of the 41 isolates (63.4%) exhibited activity against at least one of the pathogens tested. CONCLUSION: Our results suggested that P. notoginseng harbors diversified endophytic fungi that would provide a basis for the identification of new bioactive compounds, and for effective biocontrol of notoginseng root rot.