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Genetic Characterisation of the Bacterial Microbiota Associating With a Strain of Epichloë Fungal Endophyte of Perennial Ryegrass and the Interaction With Its Paenibacillus Members

Summary

Researchers discovered that cultures of a fungal endophyte found in perennial ryegrass contain complex bacterial communities dominated by Paenibacillus bacteria. These bacterial cells live on the surface of fungal filaments and regulate each other’s populations through antagonistic interactions, with one strain (E300) acting as a keystone species that controls the community structure. Despite these dynamic bacterial changes, the fungal host’s growth remained unaffected, suggesting a balanced symbiotic relationship important for the grass’s agricultural performance.

Background

Plant-associated fungi can host unique bacterial microbiota that provide multiple benefits to their fungal hosts. Epichloë fungal endophytes form symbiotic associations with perennial ryegrass and have significant ecological and agricultural importance. However, the bacterial communities associated with Epichloë endophytes and their interactions remain poorly understood.

Objective

To genetically characterize the bacterial microbiota associated with Epichloë endophyte strain AR135 isolated from perennial ryegrass using 16S rRNA gene sequencing and direct microbial isolation. The study aimed to investigate microbe-microbe interactions between these bacteria and the fungal endophyte.

Results

The bacterial microbiota of AR135 was dominated by Paenibacillus members (99% abundance), with trace amounts of Delftia and Bradyrhizobium. Paenibacillus cells were located on the surface of fungal hyphae both in vitro and in planta. E300 drastically altered bacterial microbiota abundance (63% increase) and completely eliminated E100 cells, revealing an antagonistic relationship between these two strains.

Conclusion

Epichloë fungal endophytes host bacterial communities whose structure is regulated by key members including a putative keystone taxon (E300). The findings demonstrate that ostensibly pure fungal cultures contain complex bacterial microbiota with important community dynamics. Bacterial abundance variations did not affect fungal biomass under the experimental conditions tested.
  • Published in:Environmental Microbiology Reports,
  • Study Type:Experimental Research,
  • Source: PMID: 40485104, DOI: 10.1111/1758-2229.70113
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