Chemistry of microbial symbionts from leaf cutting ants

Leaf cutting ants grow the symbiotic fungus Leucoagaricus gongylophorus that they feed with leaf material. In turn the ants use their fungus garden as major food source. This mutualistic relationship is threatened by pathogens, in particular the fungus Escovopsis weberi. But leaf cutting ant associated symbiotic Actinomyces help to protect the fungus garden of the ants by production of antifungal compounds. Recently, we identified first antifungal compounds from microbial symbionts in this interaction. Using bioassay guided fractionation we found that many of the microbial symbionts produce the well known antifungal candicidin macrolides (Figure 1).

Figure 1: Bioassay guided isolation of candicidin macrolides from microbial symbionts of leaf cutting ants. A. Microbial biofilm on the body of a leaf cutting ant (Acromyrmex octospinosus),  B. HPL-chromatogram of purified candicidin macrolides and bioassay against the pathogen E. weberi, C. Structure of candicdin D

 

Figure 2: Complex interactions

But the ecosystem of leaf cutting ants is much more complex (Figure 2). In contrast to the prevailing view, there are many microorganisms involved and also many pathogenic diseases. Thus a multitude of antibiotic and antifungal compounds can be expected from this ecosystem. The diversity of chemical compounds used by the different organisms to shape their environment can be expected to be enormous.

I. Schoenian, M. Spiteller, M., Ghaste, R. Wirth, H. Herz, D. Spiteller, Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf cutting ants, Proc. Natl. Acad. Sci. U.S.A. 2011, early online.

D. Spiteller, How do fungus growing ants protect their fungus garden against infections? Wie schützen pilz-züchtende Ameisen ihren Pilzgarten vor Infektionen? Biospektrum 2010, 2, 161-163.

S. Haeder, R. Wirth, H. Herz, D. Spiteller, Candicidin-producing Streptomyces support leaf-cutting ants to protect their fungus garden against the pathogenic fungus Escovopsis. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 4742-4746.