Metabolic picture of microbial interaction: chemical crosstalk during co-cultivation between three dominant genera of bacteria and fungi in medicinal plants rhizosphere.

INTRODUCTION: Microbial communities affect several aspects of the earth's ecosystem through their metabolic interaction. The dynamics of this interaction emerge from complex multilevel networks of crosstalk. Elucidation of this interaction could help us to maintain the balance for a sustainable future. OBJECTIVES: To investigate the chemical language among highly abundant microbial genera in the rhizospheres of medicinal plants based on the metabolomic analysis at the interaction level. METHODS: Coculturing experiments involving three microbial species: Aspergillus (A), Trichoderma (T), and Bacillus (B), representing fungi (A, T) and bacteria (B), respectively. These experiments encompassed various interaction levels, including dual cultures (AB, AT, TB) and triple cultures (ATB). Metabolic profiling by LC-QTOFMS revealed the effect of interaction level on the productivity and diversity of microbial specialized metabolites. RESULTS: The ATB interaction had the richest profile, while the bacterial profile in the monoculture condition had the lowest. Two native compounds of the Aspergillus genus, aspergillic acid and the dipeptide asperopiperazine B, exhibited decreased levels in the presence of the AT interaction and were undetectable in the presence of bacteria during the interaction. Trichodermarin N and Trichodermatide D isolated from Trichoderma species exclusively detected during coexistence with bacteria (TB and ATB). These findings indicate that the presence of Bacillus activates cryptic biosynthetic gene clusters in Trichoderma. The antibacterial activity of mixed culture extracts was stronger than that of the monoculture extracts. The TB extract exhibited strong antifungal activity compared to the monoculture extract and other mixed culture treatments. CONCLUSION: The elucidation of medicinal plant microbiome interaction chemistry and its effect on the environment will also be of great interest in the context of medicinal plant health Additionally, it sheds light on the content of bioactive constituents, and facilitating the discovery of novel antimicrobials.

LC-MS/MS and GC-MS based phytochemical perspectives and antimicrobial effects of endophytic fungus Chaetomium ovatoascomatis isolated from Euphorbia milii.

The antimicrobial activity of endophytic fungi isolated from Euphorbia milii was evaluated against Gram-positive, Gram-negative bacteria, unicellular yeast, and filamentous fungi. Chaetomium ovatoascomatis NRC was identified morphologically and genetically as the most active strain. The total ethyl acetate extract of C. ovatoascomatis NRC demonstrated significant antimicrobial activity against Gram-negative; Escherichia coli, Salmonella enteric, and fungi; Aspergillus niger with MIC of 62.5 ug/ml. Whereas n-hexane fraction demonstrated broader activity against Gram-positive; Bacillus subtilis, Lactobacillus cereus, Gram-negative; Escherichia coli and Salmonella enteric, fungi; Candida albicans and F. solani. LC-MS/MS analysis of ethyl acetate strain extract and GC-MS analysis of the n-hexane fraction were used to identify the metabolites of the strain extract. LC-MS/MS determined three major metabolites with potential antimicrobial activities including grevilline B, aflatoxin G2 and apigenin. GC-MS analysis of n-hexane fraction tentatively identified 30 compounds, where 9,12-octadecadienoic acid methyl ester was the major compound.