Interaction between workers during a short time window is required for bacterial symbiont transmission in Acromyrmex leaf-cutting ants

PLoS One. 2014 Jul 24;9(7):e103269. doi: 10.1371/journal.pone.0103269. eCollection 2014.


Stable associations between partners over time are critical for the evolution of mutualism. Hosts employ a variety of mechanisms to maintain specificity with bacterial associates. Acromyrmex leaf-cutting ants farm a fungal cultivar as their primary nutrient source. These ants also carry a Pseudonocardia Actinobacteria exosymbiont on their bodies that produces antifungal compounds that help inhibit specialized parasites of the ants' fungal garden. Major workers emerge from their pupal cases (eclose) symbiont-free, but exhibit visible Actinobacterial coverage within 14 days post-eclosion. Using subcolony experiments, we investigate exosymbiont transmission within Acromyrmex colonies. We found successful transmission to newly eclosed major workers fostered by major workers with visible Actinobacteria in all cases (100% acquiring, n = 19). In contrast, newly eclosed major workers reared without exosymbiont-carrying major workers did not acquire visible Actinobacteria (0% acquiring, n = 73). We further show that the majority of ants exposed to major workers with exosymbionts within 2 hours of eclosion acquired bacteria (60.7% acquiring, n = 28), while normal acquisition did not occur when exposure occurred later than 2 hours post-eclosion (0% acquiring, n = 18). Our findings show that transmission of exosymbionts to newly eclosed major workers occurs through interactions with exosymbiont-covered workers within a narrow time window after eclosion. This mode of transmission likely helps ensure the defensive function within colonies, as well as specificity and partner fidelity in the ant-bacterium association.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Actinobacteria / classification
  • Actinobacteria / genetics
  • Actinomycetales / classification
  • Actinomycetales / genetics
  • Actinomycetales / physiology*
  • Animal Communication*
  • Animals
  • Ants / microbiology*
  • Ants / physiology*
  • Host Specificity / genetics
  • Phylogeny
  • Plant Leaves
  • RNA, Ribosomal, 16S / genetics
  • Sequence Analysis, DNA
  • Species Specificity
  • Symbiosis* / genetics
  • Time Factors


  • RNA, Ribosomal, 16S