CAS BI 411 Study Guide - Midterm Guide: Leafcutter Ant, Nif Gene, Diazotroph
13 Mar 2018
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1_currie: symbiotic nitrogen fixation in fungus gardens of leaf-cutter ants. Determining n-content and n-fixation in fungus gardens of leaf-cutter ants. A: airtight chamber: co2 trap, moisture trap, garden chamber, feeding chamber, gas injection port. Measured n isotopic ratio of 15 : 14 : b: 1 week later, c: 2 weeks later. C: increase in n-content from leaf to refuse: lowest in fresh leaf cuttings higher in fungus garden highest in ants" refuse dump. D: ar activity highest in fungus gardens (acromyrmex and atta species) B: 1 week later: 15n-enrichmed in fungus garden, workers, brood. Two genera of nitrogen-fixing bacteria found in fungal gardens: pantoea and klebsiella (more abundant of the two) Klebsiella fixes nitrogen at an ar rate comparable to known free-living diazotroph. Phylogenetic analyses revealed that there are many ant-associated symbiotic klebsiella strains and they form a monophyletic clade. Extra: found nifh only in fungal garden, amount found in ant dna probably undigested fungus.
