Abstracts (first author)

Poster 

Identifying symbiotic gut-bacteria of fungus growing ants and mapping them on the phylogenetic tree

Author(s): Sapountzis P, Boomsma JJ, Schiøtt M

Summary:

Attine ants are good models for investigating complex biological interactions because every ant family is part of a symbiotic network with at least seven obligate participants: the fungus garden which is their primary food, Escovopsis fungus garden pathogens, cuticular Actinobacteria that produce antibiotics and their black yeast competitors, and two clades of nitrogen-fixing bacteria in gardens. However, there may be many more participants in the gut microbiome, but this community has essentially remained unexplored in spite of further mutualists being likely to occur there due to the highly specialized diets of the ants. We used 16S 454 pyrosequencing to identify gut bacteria in eight Panamanian genera of fungus-growing ants from both field and lab colonies. We complemented these data with FISH microscopy providing insight in the bacterial localization and possible roles of some of these bacteria in the ant-fungus mutualism. Mapping some of the prevalent OTUs on the attine phylogenetic tree showed a number of distinct patterns that appear consistent with major transitions in social and symbiont evolution.



Abstracts (coauthor)

Summary:

Communities or single lineages of bacterial symbionts are increasingly recognized as major fitness determinants of insects, and they are particularly likely to be mutualists when host diets are specialized and partially deficient. Some insect hosts have independently domesticated related microbes to meet similar challenges, but whether hosts with different life histories can maintain the same symbionts merely by sharing the same food niche has not been explicitly investigated. The nest-sharing symbiosis between Megalomyrmex social parasites (Formicidae: Solenopsidini) and their fungus-growing ant hosts (Formicidae: Attini) provides a unique opportunity to address this question, as both lineages rely on the same narrow fungal diet, but are only distantly related. We used a combination of 454 pyrosequencing and diagnostic PCR screening to map the diversity of bacteria associated with Megalomyrmex ants across their phylogenetic tree, which also contains clades of free-living generalist predators. We show that a specific group of Entomoplasmatales is associated with socially parasitic ‘thief-ant’, ‘agropredator’ and ‘guest-ant’ lineages of Megalomyrmex and appears to be derived from and always shared with the attine host ants. Moreover, the microbiotas of guest-ants appear to be completely dominated by a specific Bartonellaceae lineage, which can but does not need to be accompanied by the Entomoplasmatales bacteria. Bartonellaceae are native to the guest-ants and are secondarily transmitted to some (ca 40%) but not all host colonies. Our results suggest that host and socially parasitic ants contribute their own vertically transmitted bacteria to their permanent symbiosis and that these bacteria can be asymmetrically transmitted to the partner species via the fungus-garden that they share. The function of these endosymbionts remains unknown.

Summary:

Fungus-growing ants live in a complex symbiosis involving both fungal and bacterial partners. Among these are Actinobacteria of the genus Pseudonocardia that are maintained on the ant cuticle to produce antibiotics, primarily against a parasitic fungus of the garden symbiont. The symbiosis has been assumed to be a hallmark of evolutionary stability, but this notion has been challenged by culturing and sequencing data. We used 454 pyrosequencing of 16S rRNA to estimate the diversity of the cuticular bacterial community of the leaf-cutting ant Acromyrmex echinatior from Panama. We used field and lab samples of the same colonies, the latter after colonies had been kept under laboratory conditions for up to 10 years. We show that the bacterial communities are highly colony-specific and stable over time. The majority of colonies (25/26) had a single dominant Pseudonocardia strain and only two strains were found in the Gamboa population across 17 years, confirming an earlier study. The microbial community on newly hatched ants consisted almost exclusively of Pseudonocardia while other Actinobacteria were identified in lower abundances on older ants. These findings are consistent with recent theory predicting that mixtures of antibiotic-producing bacteria can remain mutualistic when dominated by a single vertically transmitted strain.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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