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Nutrition

Nutrition. how organisms obtain energy and carbon to make organic compounds diverse in prokaryotes. Energy Sources. Light phototrophs Inorganic chemicals (eg. H 2 S, NH 3 , Fe 2+ ) chemotrophs Organic compounds chemotrophs. Carbon Sources. CO 2 autotroph (self feeder)

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Nutrition

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  1. Nutrition • how organisms obtain energy and carbon to make organic compounds • diverse in prokaryotes

  2. Energy Sources • Light • phototrophs • Inorganic chemicals (eg. H2S, NH3, Fe2+) • chemotrophs • Organic compounds • chemotrophs

  3. Carbon Sources • CO2 • autotroph (self feeder) • Organic Compounds • heterotroph (other feeder)

  4. Photoautotrophs • energy from light • carbon from CO2 • most plants, some protists • most photosynthetic prokaryotes

  5. example • cyanobacteria • H2O + CO2 with light • releases oxygen

  6. another example • Purple sulfur bacteria • H2S + CO2 with light • releases sulfur • also green sulfur bacteria • light from hydrothermal vents!

  7. Chemoautotrophs • energy from inorganic chemicals • carbon from CO2 • only certain prokaryotes

  8. symbiosis • 2 kinds of organisms live in direct contact • symbiont is smaller one (vs host)

  9. example • tube worm symbionts • live inside tube worms • Use H2S, CO2 gathered by host. • Make food for both.

  10. Photoheterotrophs • energy from light • carbon from organic compounds • certain prokaryotes

  11. example • purple nonsulfur bacteria • accessory pigments—absorb diff.  • bacteriochl a • blue • carotenoids • yellow, red

  12. Chemoheterotrophs • energy and carbon from organic compounds • most prokaryotes and protists, fungi, animals, some plants

  13. example • lactic acid bacteria • including Lactobacillus • yogurt • requires many nutrients • human gut, vagina • “probiotics”?

  14. History of Early Life • 4.5 bya the Earth formed conditions extreme • 100 °C, CH4, CO2, H2S, Fe2+, N2, NH3 • 3.5 bya first fossil evidence of life: complex cyanobacteria • 3.2 bya fossils from hydrothermal vent community

  15. stromatolite: fossil colony of cyanobacteria Ancient cyanobacteria look like modern ones Knoll, A.H. (2003) Life on a Young Planet: The First Three Billion Years of Evolution on Earth. Princeton University Press, Princeton, New Jersey. (Milner Library, 5th floor)

  16. Cyanobacteria produced O2 Atmosphere • H2O + CO2 (w/light) ---> glucose + O2 • O2 precipitates iron (sea & land) before accumulates • 2.5 bya banded iron formations • 2 bya O2 accumulates in atmosphere • O2 is pollutant-breaks chemical bonds

  17. oxygen and metabolism • obligate aerobes require O2 • obligate anaerobes killed by O2 • facultative anaerobes OK either way

  18. some prokaryotes survived: • 1) anaerobic habitats (no O2) • 2) evolved antioxidant mechanisms • 3) used O2 as electron receptor • major innovation • aerobic resp evolved • more complex life forms possible

  19. some prokaryotes can fix nitrogen • N N is N2 in air • enzyme nitrogenase • N2-->NH3 (ammonia)

  20. examples: symbiotic nitrogen fixers • 1) Rhizobium • root nodules of legumes (eg soybeans) • N for plant and field • 2) Anabaena (cyanobacterium) • in water fern Azolla • rice fields

  21. nitrogen fixation & oxygen • O2 poisons nitrogenase • cyanobacterial strategies: • 1) avoid oxygen • 2) PS & N-fix diff places or times • 3) special N-fix cells—heterocytes • formerly heterocysts

  22. summary • diverse biochemistry • create and adapt to environment • put together & take apart almost all molecules of modern life • cyanobacteria most self-sufficient: need light, CO2, N2, H2O, minerals

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