Dual defense mechanisms from a novel marine fungus Nigrograna chlamydospora sp. nov. B143: antifungal and anti-aflatoxigenic properties against Aspergillus flavus

Introduction A novel strain with strong antagonistic and anti-aflatoxigenic activity against Aspergillus flavus was isolated from a marine environment, highlighting its potential for biocontrol applications in food and agriculture. Methods The strain, designated B143, was identified using a polyphasic taxonomic approach combining morphological observation and phylogenetic analysis. Its petroleum ether extract was tested for inhibitory effects on hyphal growth, spore germination, and aflatoxin B1 production in A. flavus . Transcriptome analysis was conducted to identify differentially expressed genes in aflatoxin and ergosterol biosynthesis pathways. Fluorescence staining was used to assess cell wall and membrane integrity, as well as oxidative stress. Results Strain B143 was identified as a new species, Nigrograna chlamydospora sp. nov. Its petroleum ether extract significantly inhibited hyphal growth (70.84 ± 4.29%) and spore germination (98.23 ± 0.10%), and reduced aflatoxin B1 production by 35.88%. Transcriptome analysis showed down-regulation of key genes in aflatoxin B1 (adhA, 1.2-fold) and ergosterol (erg5, 1.6-fold) biosynthesis pathways. Fluorescence staining confirmed disruption of cell wall and membrane integrity and induction of oxidative stress in A. flavus . Discussion These findings demonstrate that N. chlamydospora B143 exhibits strong dual inhibitory effects against A. flavus growth and aflatoxin production, underscoring its potential as an effective biocontrol agent for mitigating contamination in food and agricultural products.