Attine ant microbiome
Samples of cuticular bacteria of multiple individuals and species of attine ants Targeted Locus (Loci)
Fungus-growing (attine) ants live in a complex multi-trophic symbiosis that involves both fungal and bacterial partners. Among these are Actinobacteria of the genus Pseudonocardia that are maintained on the ant cuticle to produce antibiotics, primarily against a parasitic fungus of their garden symbiont. This association has been assumed to be a hallmark of evolutionary stability, but this notion has recently been challenged by culturing and sequencing data indicating that the actinobacterial cultures can be relatively diverse and variable. We used 454 pyrosequencing of a region of the 16S rDNA gene to estimate the diversity of the bacterial community on the cuticle of the leaf-cutting ant Acromyrmex echinatior and some other sympatric fungus-growing ants from Gamboa, Panama. Cuticular bacterial cultures tend to be concentrated on the ventral side of the ant thorax, so we restricted our sampling to include only the laterocervical plates and pronotum with abundant bacterial cover. We used both field and lab samples of the same colonies, the latter after colonies had been kept under laboratory conditions for up to 10 years. We show that the cuticular bacterial communities are highly colony-specific and stable over time. The majority of colonies (25/26) had a single dominant Pseudonocardia strain and only two such strains were found in the Gamboa population across 17 years of sampling, confirming an earlier study using elongation factor 1a (EF-1a). A number of other Actinobacteria were identified at lower densities in some samples, but no consistent patterns were observed. We suggest several directions in which future studies may shed light on the interaction-specificity of this symbiosis, which apparently can be very different across species and allopatric populations of fungus-growing ants.