Dentigerumycin: a bacterial mediator of an ant-fungus symbiosis

Abstract

Fungus-growing ants engage in mutualistic associations with both the fungus they cultivate for food and actinobacteria (Pseudonocardia spp.) that produce selective antibiotics to defend that fungus from specialized fungal parasites. We have analyzed one such system at the molecular level and found that the bacterium associated with the ant Apterostigma dentigerum produces dentigerumycin, a cyclic depsipeptide with highly modified amino acids, to selectively inhibit the associated parasitic fungus (Escovopsis sp.).

Figure 1

(a) Apterostigma fungus-growing ant (colony code CC011120-4), showing a worker of Apterostigma dentigerum. (b) Pairwise challenge bioassay demonstrates in vitro inhibition of the parasitic fungus Escovopsis (top and bottom) by Pseudonocardia (center) (8.5 cm diameter agar plate).

Figure 1

(a) Apterostigma fungus-growing ant (colony code CC011120-4), showing a worker of Apterostigma dentigerum. (b) Pairwise challenge bioassay demonstrates in vitro inhibition of the parasitic fungus Escovopsis (top and bottom) by Pseudonocardia (center) (8.5 cm diameter agar plate).

Figure 2

(a) The structure of dentigerumycin (1) contains highly modified amino acid units such as piperazic acids. (b) The susceptibility dose response curve plotting log concentration dentigerumycin in μM vs fungal cell density (fluorescence unit) of Escovopsis, demonstrating inhibition of the parasitic fungus by dentigerumycin with MIC of 2.8 μM.

Figure 2

(a) The structure of dentigerumycin (1) contains highly modified amino acid units such as piperazic acids. (b) The susceptibility dose response curve plotting log concentration dentigerumycin in μM vs fungal cell density (fluorescence unit) of Escovopsis, demonstrating inhibition of the parasitic fungus by dentigerumycin with MIC of 2.8 μM.