a-visual-guide-for-studying-behavioral-defenses-to-pathogen-attacks

A Visual Guide for Studying Behavioral Defenses to Pathogen Attacks in Leaf-Cutting Ants

The complex lifestyle, evolutionary history of advanced cooperation, and disease defenses of leaf-cutting ants are well studied. Although numerous studies ...

University of Copenhagen

The attine ants of South and Central America are ancient farmers, having evolved a symbiosis with a fungal food crop >50 million years ago. The most evolutionarily derived attines are the  and  leafcutter ants, which harvest fresh leaves to feed their fungus.  and many other attines vertically transmit a mutualistic strain of  and use antifungal compounds made by these bacteria to protect their fungal partner against co-evolved fungal pathogens of the genus .  mutualists associated with the attines  and  make novel cyclic depsipeptide compounds called gerumycins, while a mutualist strain isolated from derived  makes an unusual polyene antifungal called nystatin P1. The novelty of these antimicrobials suggests there is merit in exploring secondary metabolites of  on a genome-wide scale. Here, we report a genomic analysis of the  phylotypes Ps1 and Ps2 that are consistently associated with  ants collected in Gamboa, Panama. These were previously distinguished solely on the basis of 16S rRNA gene sequencing but genome sequencing of five Ps1 and five Ps2 strains revealed that the phylotypes are distinct species and each encodes between 11 and 15 secondary metabolite biosynthetic gene clusters (BGCs). There are signature BGCs for Ps1 and Ps2 strains and some that are conserved in both. Ps1 strains all contain BGCs encoding nystatin P1-like antifungals, while the Ps2 strains encode novel nystatin-like molecules. Strains show variations in the arrangement of these BGCs that resemble those seen in gerumycin gene clusters. Genome analyses and invasion assays support our hypothesis that vertically transmitted Ps1 and Ps2 strains have antibacterial activity that could help shape the cuticular microbiome. Thus, our work defines the  species associated with  ants and supports the hypothesis that  species could provide a valuable source of new antimicrobials.

Genome Analysis of Two  Phylotypes Associated with  Leafcutter Ants Reveals Their Biosynthetic Potential.

Acromyrmex leafcutter ants form a mutually beneficial symbiosis with the fungus Leucoagaricus gongylophorus and with Pseudonocardia bacteria. Both are vertically transmitted and actively maintained by the ants. The fungus garden is manured with freshly cut leaves and provides the sole food for the ant larvae, while Pseudonocardia cultures are reared on the ant-cuticle and make antifungal metabolites to help protect the cultivar against disease. If left unchecked, specialized parasitic Escovopsis fungi can overrun the fungus garden and lead to colony collapse. We report that Escovopsis upregulates the production of two specialized metabolites when it infects the cultivar. These compounds inhibit Pseudonocardia and one, shearinine D, also reduces worker behavioral defenses and is ultimately lethal when it accumulates in ant tissues. Our results are consistent with an active evolutionary arms race between Pseudonocardia and Escovopsis, which modifies both bacterial and behavioral defenses such that colony collapse is unavoidable once Escovopsis infections escalate.

Article	Year
Genome Analysis of Two Phylotypes Associated with Leafcutter Ants Reveals Their Biosynthetic Potential. Frontiers in microbiology\| PubMed ID: 28082956	2016
Chemical warfare between leafcutter ant symbionts and a co-evolved pathogen. Nature communications\| PubMed ID: 29880868	2018

Tabitha M. Innocent

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