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ATTINE ANTS have been a theme at my blog recently. They first showed up in a discussion of their evolutionary tree, then in a post examining their relationship with the actinomycete bacteria that help protect their fungal gardens from parasites. In my reading I stumbled across the article that I will write about today, which seems to have discovered another part to the attine ant symbiosis. As of now this is the sole report on the occurrence of black yeasts living apparently parasitically on the attine ants, reliant upon the cuticular crypts that normally house helpful actinomycetes.
WHILE THE ATTINE ants are not well-studied, I posted this week about a study into their evolution that revealed the history of innovations in their cultivation of fungus. The attine ants are part of a symbiotic network between the ants, their fungal cultivars, the parasitic fungus Escovopus, and actinomycete bacteria that serve to suppress this parasite. These bacteria are members of Pseudonocardia and grow in filamentous mycelia on the insects’ integument, where the ants have evolved cuticular crypts to house the bacteria and glandular secretions that support their growth.
The actinomycetes are an order of bacteria that are know to produce a wide range of biologically active molecules, many of which are active against other bacteria and against fungi. Some of these natural products are now used clinically, such as the antibacterial antibiotics streptomycin, erythromycin, and tetracycline, anticancer drugs daunorubicin and doxorubicin, and antifungal drugs amphotericin B and natamycin. Actinomycetes inhabit a variety of environments, but many are ubiquitous soil bacteria.
THE ATTINE ANTS are a clade of New World ants that cultivate fungal gardens for use as a food source. The most widely known group are the leaf-cutter ants, which spend most of their time harvesting slices of leaves that are chewed up and placed in the fungal gardens in their underground colonies. There are many other lesser-known species, and these practice different forms of fungal agriculture. A new study of the phylogenetics of attine ants show that the different methods of fungal cultivation emerged in single events.