Microbe Vs. Microbe: Bacterial and Fungal Cultivar Interactions in a Fungus-Farming Ant System

S. M. Kopac, J. Klassen

Author address: 

Univ. of Connecticut, Storrs, CT


Microbes live in close association with one another in the Trachymyrmex septentrionalis fungusfarming ant system, providing a framework for potentially undiscovered and understudied microbial interactions. Leafcutter ants, which belong to the same tribe as Trachymyrmex, are characterized by evolutionarily conserved interactions between pathogens and protective bacteria carried by the ants; similar dynamics might exist in the T. septentrionalis system. Interestingly, the role of bacteria living in the fungus garden (the cultivar) are not well characterized in either system. From a preliminary survey of 33 strains of fungus garden bacteria we identified over a dozen species, including Actinomycetales, Enterobacteriaceae, Lactobacillales and Bacillales. We found that many of these microbes have negative or positive effects on each other’s growth. In the present study we focus on the interactions between these bacteria and with that of the cultivar.We characterized bacterial isolates to the species level and determined if they are persistent or transient members of the cultivar community by identifying conserved clades in a phylogeny of isolates from multiple fungus gardens. Conserved clades could be the result of bacterial-bacteria or cultivar-bacteria interactions on the assembly and maintenance of the fungus garden bacterial community or the result of abiotic conditions.Interactions between microbes from our system were assessed by growth assays; cross-streak growth assays for inhibition and spot plate co-cultures for beneficial and mutually beneficial interactions. The effect of bacteria on cultivar growth was tested using pour plate assays with an overlay. We tested for coevolution at the colony level by comparing the number of interactions between bacteria and bacteria/cultivar from the same colony vs. from different colonies. We also tested close relatives of bacterial isolates to determine if specialization to fungus gardens occurs at the clade level.In collaboration with JGI, the genomes of several isolates were sequenced using SMRT technology developed by PacBio. Genome content comparisons were made, with specific focus on genes associated with secondary metabolites and other forms of microbial interaction and communication. Secondary metabolites possess a variety of functions including antibacterial, antifungal, anti-malarial and anti-cancer properties.

abstract No: 


Full conference title: 

ASM Microbe 2016
    • ASM microbe 1st (2016)