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Microbiota of Attine Ants' Gardens: Visualizing a Microbial Landscape by Scanning Electron Microscopy
Published on: October 4, 2024
Coevolution between attine ants and actinomycete bacteria: a reevaluation
Ulrich G Mueller1, Debadutta Dash, Christian Rabeling
1Section of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA. umueller@mail.utexas.edu
Evolution; International Journal of Organic Evolution
|August 30, 2008
Summary
Coevolution between fungus-gardening ants and actinomycete bacteria is challenged. Ants frequently acquire Pseudonocardia from the environment, not through specific coevolution, requiring revised models of this mutualism.
Area of Science:
- Microbiology
- Evolutionary Biology
- Entomology
Background:
- Actinomycete bacteria are vital metabolic mutualists, aiding in nitrogen fixation and antibiotic production.
- Pseudonocardia actinomycetes are believed to suppress diseases in the gardens of fungus-gardening (attine) ants.
- The coevolutionary relationship between attine ants and actinomycetes is a key area of study.
Purpose of the Study:
- To reassess the coevolutionary dynamics between actinomycete bacteria and attine ants.
- To investigate the origins and acquisition patterns of Pseudonocardia in attine ant colonies.
- To evaluate prevailing models of Pseudonocardia-disease coevolution in ant gardens.
Main Methods:
- Phylogenetic analysis using culture-dependent and culture-independent microbial surveys.
- Comparison of bacterial phylogenies with ant phylogenies.
- Isolation of actinomycete bacteria from ant gardens, starter cultures, and environmental sources (soil, plants).
Main Results:
- Phylogenetic analysis revealed close affinities between free-living and ant-associated Pseudonocardia.
- No significant topological correspondence was found between ant and Pseudonocardia phylogenies, indicating frequent environmental acquisition.
- Pseudonocardia was rare in Atta leafcutter ants, suggesting contamination, while Mycobacterium and Microbacterium were common.
- Evidence suggests ants acquire Pseudonocardia from soil and plants.
Conclusions:
- The prevailing view of specific coevolution between Pseudonocardia and attine ants is not supported by phylogenetic evidence.
- Frequent acquisition of Pseudonocardia from environmental sources necessitates revision of current coevolution models.
- The effectiveness of Pseudonocardia antibiotics may stem from environmental recruitment rather than an evolutionary arms race with garden diseases.
- While attine ants show modifications associated with actinomycetes, reciprocal bacterial modification remains unproven, challenging the definition of coevolution.
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