Diet Shapes Bacterial Communities in Leafcutter Ant Fungal Gardens
Scientists have discovered that the bacterial communities within leafcutter ant colonies are significantly influenced by the diet provided to their symbiotic fungus. This research, published in NPJ Biofilms and Microbiomes, offers insights into the complex functioning of these colonies and holds potential for discovering novel molecules with applications in biofuels and bioremediation.
The Leafcutter Ant Ecosystem
Leafcutter ants (tribe Attini) are renowned for their unique agricultural practice: cultivating a fungus that digests organic matter, providing essential nutrients to the ant colony in exchange for food and protection. [1] These colonies are not simple partnerships but complex ecosystems teeming with various fungi and bacteria, creating a multitude of interactions and producing a diverse range of compounds.
Dietary Influence on Bacterial Communities
Researchers at São Paulo State University (UNESP) and the University of São Paulo (USP) investigated how bacterial communities respond to different diets offered to the cultivated fungus. Their findings echo research on the human gut microbiota, demonstrating that the microbial composition of ant colonies shifts according to dietary changes.
The study revealed that a diet consisting solely of fruits and grains fostered a bacterial community markedly different from those fed the typical leafcutter ant diet of fresh and dry leaves. Interestingly, the symbiotic fungus ceased growth in colonies receiving only fruits and grains, as these simpler fibers are more easily digested, disrupting the nutritional balance for the ants. This suggests the fungus and its associated bacteria are adapted to process more complex fibers, yielding greater nutritional value.
Experimental Design
The research involved 28 colonies of lemon leaf-cutter ants (Atta sexdens) divided into four groups and fed different diets for 56 days. The control group received only leaves, mimicking their natural diet. Other groups were fed exclusively grains (oats and rice) and fruits (dehydrated papaya, banana, and apple), a generalist diet alternating between leaves, fruits, and grains, and a fluctuating diet of leaves, then fruits and grains, then back to leaves.
“Just as observed in the human gut, the microbiota of colonies responds to the diet and can return to their original composition when the previous diet is reintroduced,” explains Mariana de Oliveira Barcoto, the study’s first author.
A Longitudinal Continuum of Degradation
The researchers observed a longitudinal continuum of lignocellulose degradation within the colony. Freshly collected leaves are deposited in an upper, grayish-green layer with sparse microbial colonization. As organic matter breaks down, microbial density increases, forming whitish central regions containing gongylids – nutrient-rich structures for the ants. Undegraded plant parts accumulate in the oldest, brownish region at the bottom, each harboring distinct bacterial groups.
Worker ants diligently remove non-nutritive waste, depositing it in a separate “trash pile” where further bacterial action occurs.
Biotechnological Potential of Waste Products
The discarded waste material holds significant biotechnological promise. The microorganisms and enzymes involved in degrading organic matter, such as lignocellulose, could be valuable for research into biofuels and bioremediation. [3]
Future Research Directions
This study opens avenues for further investigation, including exploring the effects of varying temperature and humidity on microbial responses. Researchers likewise plan to examine different ant species and parameters, potentially predicting ecosystem responses to climate change scenarios. [2]
“We altered just one variable – the diet – of a single ant species, and yet we observed major changes in the colonies. In future studies, we can explore other species and parameters and even strive to predict their effect on the ecosystem in climate change scenarios,” concludes André Rodrigues, a researcher at the Center for Research on Biodiversity Dynamics and Climate Change (CBioClima).
The article “You are what your fungus eats: diet shapes the microbial garden of a fungus-growing ant” can be read at nature.com/articles/s41522-025-00876-7.