Diversity analysis of endohyphal bacteria in oil-producing fungi inhabiting arid environments.

Introduction: Endohyphal bacteria are microorganisms that inhabit fungal hyphae or reproductive structures, which influence fungal physiology and contribute to broader ecosystem processes. However, current knowledge regarding endohyphal bacteria associated with oil-producing fungi in arid environments remains scarce and warrants further investigation. Method: Oil-producing fungi were isolated and screened from arid soil samples collected in Toksun County, Xinjiang, China. A preliminary assessment of the presence of endohyphal bacteria within these fungi was conducted using SYTO 9 green fluorescent staining. High-throughput sequencing was employed to analyze the distribution patterns and community composition of the endohyphal bacteria. Results: Endohyphal bacteria were detected in 16 fungal strains, which constituted 61.5% of the total 26 oil-producing strains obtained. High-throughput sequencing analysis identified 63 amplicon sequence variants (ASVs) belonging to 6 phyla and 35 genera, with Proteobacteria representing the dominant phylum. Most fungi contained multiple endohyphal bacterial taxa and exhibited pronounced interspecific variation in community composition. Functional prediction analysis indicated a significant enrichment of pathways related to metabolism, environmental information processing, and genetic information processing in the endohyphal bacteria associated with distinct fungal hosts. Discussion: Oil-producing fungi may establish interactive systems through symbiotic associations with diverse endohyphal bacteria. These symbiotic interactions may promote lipid accumulation and enhance ecological adaptability in oil-producing fungi, potentially mediated by the metabolic synergy and functional complementarity described above. In conclusion, this study provides a preliminary characterization of the diversity and community structure of endohyphal bacteria associated with oil-producing fungi in arid environments, establishing a basis for future investigations into their functional interactions.