Acromyrmex Leaf-Cutting Ants Have Simple Gut Microbiota with Nitrogen-Fixing Potential

Area of Science:

• Insect-microbe mutualisms
• Gut microbiome research
• Symbiotic relationships in ants

Background:

• Fungus-farming ants and termites evolved independently.
• Termites retain diverse gut microbiota, but ant gut bacteria remain uninvestigated.
• Ants' exclusively fungal diet raises questions about nutritional specialization.

Purpose of the Study:

• Characterize the gut bacterial community of Panamanian Acromyrmex ants.
• Investigate bacterial specialization in fungus-growing ants on a fungal diet.
• Determine the role of gut symbionts in ant nutrition.

Main Methods:

• Gut bacterial community analysis in Acromyrmex ants.
• Localization of bacterial symbionts within ant gut tissues.
• Dietary manipulation using tetracycline to assess symbiont roles.
• Analysis of bacterial NifH protein production.

Main Results:

• Acromyrmex gut bacteria dominated by four taxa: Wolbachia, Rhizobiales, and two Entomoplasmatales.
• Entomoplasmatales are intracellular/extracellular; Wolbachia is mainly intracellular; Rhizobiales form extracellular biofilms.
• Tetracycline reduced Entomoplasmatales, with minor effects on Wolbachia and moderate effects on Rhizobiales.
• Rhizobiales symbionts produce NifH proteins, indicating nitrogen fixation.

Conclusions:

• Acromyrmex ants harbor a specialized gut microbiome.
• A biofilm-forming Rhizobiales symbiont likely aids nitrogen acquisition.
• Gut symbionts may alleviate nutritional limitations of a fungus-farming diet.