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

Panax notoginseng-microbiota interactions: From plant cultivation to medicinal application

BACKGROUND

Microbiomes and their host plants are closely linked with each other; for example, the microbiome affects plant growth, fitness, nutrient uptake, stress tolerance and pathogen resistance, whereas the host plant supports the photosynthetically carbon-rich nutrition of the microbiome. The importance of the microbiome in plant‒soil ecosystems is unquestioned and has expanded to influence the medicinal application of some herbal plants via the gut microbiota.

PURPOSE

Herbal plant-microbiome interactions may provide novel knowledge to enhance the robustness of herbal plant crop performance and medicinal applications, which requires a systematic review and preceding discussion.

STUDY DESIGN AND METHODS

The interactions between Panax notoginseng and microorganisms (from soil to host) were reviewed from the literature. The terms "Panax notoginseng" and "microbiota" were used in combination with the keywords "microbiota/microbes", "bacteria/bacterium" or "fungi/fungus" or "endophyte", as well as our targeted bioactive phytochemicals, including saponins and ginsenosides.

RESULT

Our study focuses on the famous medicinal herb Panax notoginseng F. H. Chen and proposes that the microbiota is a crucial participant not only in the cultivation of this herbal plant but also in its medicinal application. We also summarize and discuss how these plant‒microbe co-associations shape the assembly of plant-related microbiomes and produce bioactive phytochemicals, as well as influence beneficial herbal traits, such as herbal plant health and pharmacology. In addition, we also highlight future directions.

CONCLUSION

The rhizosphere and endophytic microbiome of Panax notoginseng are indirectly or directly involved in plant health, biomass production, and the synthesis/biotransformation of plant secondary metabolites. Harnessing the microbiome to improve the quality of traditional Chinese medicine and improve the value of medicinal plants for human health is highly promising.

Nocardia sputi sp. nov. isolated from the sputum of patients with pulmonary infection

Two Gram-stain-positive, aerobic and rod-shaped actinomycetes (strains CY18T and CY8) were isolated from the sputum of two patients with pulmonary infections, and their taxonomic status was investigated. The 16S rRNA gene sequences and the results of phylogenetic analyses indicated that CY18T and CY8 were identical (100 %) and were most closely related to Nocardia beijingensis CGMCC 4.1521T (99.9 %) and Nocardia araoensis NBRC 100135T (99.5 %). The predominant cellular fatty acids of CY18T and CY8 were C16 : 0, C18 : 0, C18 : 1ω9c and summed feature 3 (comprising C16 : 1ɷ7c and/or C16 : 1ɷ6c), and the major menaquinone was MK-8(H4ω-cycl).The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. The whole-cell hydrolytic sugar pattern consisted of arabinose and glucose. The polar lipid profile contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, two unidentified phospholipids, three unidentified glycolipids and two unidentified lipids.The DNA G+C contents of CY18T and CY8 were 67.9 and 68.0 % respectively. The digital DNA–DNA hybridization and average nucleotide identity values between the two novel strains and closely related species were well under the 70 % and 95–96 % thresholds, respectively, but these values between the two novel strains were 95.5 % and 99.5 %, respectively. On the basis of morphological and chemotaxonomic characteristics and the results of phylogenetic analyses, strains CY18T and CY8 represent a novel species of the genus Nocardia , for which the name Nocardia sputi sp. nov. is proposed. The type strain is CY18T (=GDMCC 1.3318T = JCM 33932T).

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.