The microbial garden of fungus-growing ants: Distinct lignocellulosic profile and spatial structure, yet a similar microbiota

Background Obligate microbial gardeners, attine ants cultivate fungi for food using mostly plant-derived substrates for nourishing their fungal crops. The fungal crop grows together with its associated microbiota then forming the microbial garden, a spongy structure scaffolded by substrates. Attines differ in their cultivation systems, in part, by foraging for a diverse set of plant substrates. Here, we hypothesize that the garden lignocellulosic profile, microbiota composition, and garden spatial structure differ between attine species according to their substrate preferences. Results We sampled young and old garden regions, as well as waste material from attines representing the lower fungiculture ( Apterostigma sp., Mycetophylax sp., and Mycocepurus sp.), the higher fungiculture ( Mycetomoellerius sp.), and leaf-cutting fungiculture ( Acromyrmex coronatus and Atta sexdens ). Then, we determined the garden chemical composition via ¹³ C NMR, the microbiota composition by 16S rRNA sequencing, and spatial distribution using SEM. We found plant-derived fragments representing the majority of recognizable substrates, providing the spatial framework of the microbial garden. In consonance, it exhibits a lignocellulosic nature, which is modified to a greater extent in gardens of lower fungiculture systems than in the higher and leaf-cutting ones. In lower attine, Burkholderia is an abundant microbial member, considered part of the fungiculture core microbiota and a biomarker of lower and higher fungiculture systems. In higher and leaf-cutting gardens, otherwise, Mesoplasma is abundant, taken as a signature of leaf-cutting systems. Group-wise comparisons revealed only At. sexdens differing from other fungiculture systems by showing lower diversity. Conclusions All attine gardens, but At. sexdens , share a similar taxonomic composition. Our findings unveil biofilms as intrinsic and ubiquitous components of attine microbial gardens. Essentially, each fungiculture has its characteristic architecture, emphasizing the substrate role in shaping the garden’s spatial organization.