Chapter 25: Symbiosis Terms: Mutualism, Commensalism, and Parasitism Ecto/Endo symbionts

1. Chapter 25: Symbiosis Terms: Mutualism, Commensalism, and Parasitism Ecto/Endo symbionts Endosymbiont hypothesis Examples: Lichen --- fungi/cyanobacterium mutualism --- pioneer organisms, soil formers --- pollution biomarkers

2. Rhizosphere --- provide nutrients (mostly usable nitrogen, but also S & P)) --- defense --- are feed by plants (up to 40% of photosynthetic yield of plant may be used here) --- not all positive  denitrification Mycorrhizae --- fungi --- increase surface area for nutrient absorption --- defense

3. Root nodules: --- anaerobic location of conversion of N2 to NH3 --- leghemoglobin --- mutualistic --- allows plant to grow in nitrogen poor soils, possible target for future plant genetic engineering

5. Other Symbioses Insect-bacteria termites --- harbor protists and bacteria that help break down cellulose aphids --- Buchnera, gamma-proteobacterium genus that lives in strict mutulaistic relationship with one species of aphid (each aphid species harbors a different Buchnera) --- bacterium synthesizes amino acids and vitamins that aphid cannot make, weirdly enough some of the synthetic genes are from the host.

6. Ruminants --- successful group of mammals --- multi-chambered stomach houses bacteria to help break down cellulose --- efficiency of break down directly affects conversion of plant mass to meat --- produce considerable methane