Gray Lab

Research Overview

Ant collection

The concept that bacterial symbionts of insects are a promising source for novel natural products started with the discovery that fungus-growing ants use antibiotic-producing Actinobacteria to derive antibiotics to inhibit pathogens. This work represented the first example in nature of an animal using symbiotic Actinobacteria to derive antibiotics. Fungus-growing ants obligately depend on fungi they culture for food; if their fungus dies, so do the ants. The success of fungal cultivation by these ants is continuously threatened by specialized and potentially virulent parasitic fungi in the genus Escovopsis. The ants defend the fungus garden by engaging in a mutualistic association with filamentous Actinobacteria (genus Pseudonocardia), which produce antibiotics with potent inhibitory properties against the garden pathogen Escovopsis . Individual ant nests appear to be associated with a single strain of this bacteria. Experimental work involving the removal of the bacteria from ant workers with antibiotics resulted in rapid deterioration of the garden in those nests when infected with Escovopsis. The ants have evolved elaborate modifications for the Actinobacteria, including crypts to house the bacteria and glands that appear to produce nutrients for bacterial growth, illustrating the importance of the bacteria in suppressing diseases for these ants.

The presence and distribution of these structures support an ancient association between the ants and Pseudonocardia. Two additional lines of evidence support an early origin and coevolved association between the antibiotic-producing Pseudonocardia. First, filamentous bacteria and crypts have been found associated with a fungus-growing ant from Dominican Amber (~20mya). Second, molecular phylogenetic evidence indicates broad-scale matching of the evolutionary history of the ant-associated Pseudonocardia with those of the ants, cultivars, and Escovopsis . Following the discovery of the association between fungus-growing ants and Actinobacteria, studies have revealed that the association between antibiotic-producing Actinobacteria and insects may be widespread. For example, Actinobacteria in the genus Streptomyces are symbiotically-associated with the southern pine beetle (Dendroctonus frontalis) and European beewolves.

Ant collection

Very few research efforts have been carried out on insect-associated microorganisms, so there is an enormous potential for natural products discovery hidden in this untapped biodiversity. This ICBG will focus on these microorganisms as producers of potential therapeutic agents. Studying this underexplored source of natural products will introduce new chemical matter into highly focused primary and secondary screens that will find new therapeutic candidates for diseases with special relevance to Brazil. In addition to discovering new chemotypes from this biological source, this ICBG will also contribute to the description and preservation of microbial strains associated with invertebrates from different Brazilian biomes. It is certain that new microbial species will be isolated and characterized. Through these efforts we hope to expand the knowledge and appreciation of Brazil's microbial diversity and thereby contribute to biodiversity preservation policies in Brazil.

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