Symbiotic Complexity:

Discovery of a fifth Symbiont in the

Attine Ant-microbe Symbiosis

Authors: Ainslie Little & Cameron Currie

Presented by Nikki Donathan

Define Fungal Symbiotic Associations

Leaf cutter ants share a mutualism relationship with the fungus they harvest The term "mutualism"

describes any relationship between individuals of different species where both individuals derive a benefit.

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A Fifth Symbiont Factor

The success of the mutualism is threatened by specialized fungal parasites (Escovopsis)

Ants have a second mutualism with bacteria (Pseudonocardia) which produce antibiotics that inhibit garden parasite

Presence of fourth microbial symbiont associated: Black Yeasts (Ascomycota; Phialophora)

Black Yeast

Found in soil, plants, water, and decaying wood Act as secondary saprophytes and

oligotrophs Cause disease in humans and plants

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Black Yeast Information

Black yeasts grow on the ant’s cuticle where the mutualistic bacteria is cultivated

Purpose of Study: Discovery of a fifth symbiont

1. Establish that black yeasts are symbionts of fungus-growing ants

2. Find that it grows consistently on the ant’s cuticle

3. Discuss the importance of additional layers of complexity in symbioses

Research Set-up

Black yeasts isolated and amplified from study were from colonies of fungus-growing ants collected between 2002 and 2006 in Panama, Ecuador, and Peru

Part 1: Isolation of Microbes

To isolate, the ants were scrapped with a sterile metal utensil and then the material was spread on chitin agar and incubated at room temperature for four weeks.

The colonies grown were then transferred to a potato dextrose agar

Part 2: Localization of black yeast

Isolation of different body parts of the ant workers

Head, thorax, and abdomen

Each section was placed in 500 ul of sterile distilled H2O, centrifuged for 30 seconds, and then 100 ul were spread on chitin agar

Thorax was further examined by scraping the dorsal, ventral, and lateral surfaces and plating them separately

Method continued

DNA was extracted from cultures collected and directly from the ants

Results Part 1: Prevalence and

Distribution of the Black yeast Sampling of ant

population in Panama canal zone indicated high prevalence of black yeast among Apterpsigma pilosum colonies

Also isolated from colonies in other regions of Panama, Peru, Ecuador

Results Continued

Part 2: Localization on Black Yeast on Ant Most concentrated on

thorax

Results continued

Black yeast frequently cultured from Apterostigma worker

Other attempts to isolate from other genera of fungus-growing ants were unsuccessful

Discussion

What we now know Indicate that black yeast is a fifth symbiont Present in every population of Apterostigma Black yeast concentratted on specialized

locations on ants’ cuticle where bacterial mutualists are maintained

Suggests that black yeast may have been present in early stages of evolution of complex symbiosis of ants and fungus

Further Research?

Suggest four scenarios regarding evolutionary origin of black yeast:

1. Ants acquired by manuring their gardens with vegetation containing the endophytes

2. Black Yeast associated with ancestral ants of fungus growers

3. Black yeast underwent a host shift (host insect to ant)

4. A Black yeast- Pseudonocardia grow together in some soils

Further Research continued

Suggest further studies to tease apart interactions between black yeast and anti-microbe symbiosis

Exploration of black yeast role may indicate antagonizes the ants’ mutualistic bacteria

Questions?

Reference

Ahmadjian, Vernon & Paracer, Surindar. Symbiosis: An Introduction to Biological Associations. “Fungal Associations of Protozoa and Animals.” P 101-102. Oxford University Press. 2002.

Currie, Cameron R & Little, Ainslie E. F. “Symbiotic Complexity: Discovery of a Fifth Symbiont in the Attine Ant-microbe Symbiosis.” Evolutionary Biology. 2 July 2007. Accessed 23 September 2009. http://web.ebscohost.com/ehost/detail?vid=1&hid=12&sid=0f2d9d3e-0c87-406b-8c1f-52fa502e5894%40sessionmgr11&bdata=JnNpdGU9ZWhvc3QtbGl2ZSZzY29wZT1zaXRl#db=aph&AN=4647127