An epigenetic modifier enhances the generation of anti-phytopathogenic compounds from the endophytic fungus Chaetomium globosporum of Euphorbia humifusa

OSMAC Strategy: A promising way to explore microbial cyclic peptides

Microbial secondary metabolites are pivotal for the development of novel drugs. However, conventional culture techniques, have left a vast array of unexpressed biosynthetic gene clusters (BGCs) in microorganisms, hindering the discovery of metabolites with distinct structural features and diverse biological functions. To address this limitation, several innovative strategies have been emerged. The "One Strain Many Compounds" (OSMAC) strategy, which involves altering microbial culture conditions, has proven to be particularly effective in mining numerous novel secondary metabolites for the past few years. Among these, microbial cyclic peptides stand out. These peptides often comprise rare amino acids, unique chemical structures, and remarkable biological function. With the advancement of the OSMAC strategy, a plethora of new cyclic peptides have been identified from diverse microbial genera. This work reviews the progress in mining novel compounds using the OSMAC strategy and the applications of this strategy in discovering 284 microbial cyclic peptides from 63 endophytic strains, aiming to offer insights for the further explorations into novel active cyclic peptides.

Two Novel Plant-Growth-Promoting Lelliottia amnigena Isolates from Euphorbia prostrata Aiton Enhance the Overall Productivity of Wheat and Tomato

Euphorbiaceae is a highly diverse family of plants ranging from trees to ground-dwelling minute plants. Many of these have multi-faceted attributes like ornamental, medicinal, industrial, and food-relevant values. In addition, they have been regarded as keystone resources for investigating plant-specific resilience mechanisms that grant them the dexterity to withstand harsh climates. In the present study, we isolated two co-culturable bacterial endophytes, EP1-AS and EP1-BM, from the stem internodal segments of the prostate spurge, Euphorbia prostrata, a plant member of the succulent family Euphorbiaceae. We characterized them using morphological, biochemical, and molecular techniques which revealed them as novel strains of Enterobacteriaceae, Lelliotia amnigena. Both the isolates significantly were qualified during the assaying of their plant growth promotion potentials. BM formed fast-growing swarms while AS showed growth as rounded colonies over nutrient agar. We validated the PGP effects of AS and BM isolates through in vitro and ex vitro seed-priming treatments with wheat and tomato, both of which resulted in significantly enhanced seed germination and morphometric and physiological plant growth profiles. In extended field trials, both AS and BM could remarkably also exhibit productive yields in wheat grain and tomato fruit harvests. This is probably the first-ever study in the context of PGPB endophytes in Euphorbia prostrata. We discuss our results in the context of promising agribiotechnology translations of the endophyte community associated with the otherwise neglected ground-dwelling spurges of Euphorbiaceae.

Chemical diversity and biological activities of specialized metabolites from the genus Chaetomium: 2013-2022

Chaetomium (Chaetomiaceae), a large fungal genus consisting of at least 400 species, has been acknowledged as a promising resource for the exploration of novel compounds with potential bioactivities. Over the past decades, emerging chemical and biological investigations have suggested the structural diversity and extensive potent bioactivity of the specialized metabolites in the Chaetomium species. To date, over 500 compounds with diverse chemical types have been isolated and identified from this genus, including azaphilones, cytochalasans, pyrones, alkaloids, diketopiperazines, anthraquinones, polyketides, and steroids. Biological research has indicated that these compounds possess a broad range of bioactivities, including antitumor, anti-inflammatory, antimicrobial, antioxidant, enzyme inhibitory, phytotoxic, and plant growth inhibitory activities. This paper summarizes current knowledge referring to the chemical structure, biological activity, and pharmacologic potency of the specialized metabolites in the Chaetomium species from 2013 to 2022, which might provide insights for the exploration and utilization of bioactive compounds in this genus both in the scientific field and pharmaceutical industry.

Recent Advances in Search of Bioactive Secondary Metabolites from Fungi Triggered by Chemical Epigenetic Modifiers

Genomic analysis has demonstrated that many fungi possess essential gene clusters for the production of previously unobserved secondary metabolites; however, these genes are normally reduced or silenced under most conditions. These cryptic biosynthetic gene clusters have become treasures of new bioactive secondary metabolites. The induction of these biosynthetic gene clusters under stress or special conditions can improve the titers of known compounds or the production of novel compounds. Among the inducing strategies, chemical-epigenetic regulation is considered a powerful approach, and it uses small-molecule epigenetic modifiers, which mainly act as the inhibitors of DNA methyltransferase, histone deacetylase, and histone acetyltransferase, to promote changes in the structure of DNA, histones, and proteasomes and to further activate cryptic biosynthetic gene clusters for the production of a wide variety of bioactive secondary metabolites. These epigenetic modifiers mainly include 5-azacytidine, suberoylanilide hydroxamic acid, suberoyl bishydroxamic acid, sodium butyrate, and nicotinamide. This review gives an overview on the method of chemical epigenetic modifiers to trigger silent or low-expressed biosynthetic pathways to yield bioactive natural products through external cues of fungi, mainly based on the research progress in the period from 2007 to 2022. The production of about 540 fungal secondary metabolites was found to be induced or enhanced by chemical epigenetic modifiers. Some of them exhibited significant biological activities such as cytotoxic, antimicrobial, anti-inflammatory, and antioxidant activity.