1. Metabolic Diversity
Overall, the chemical reactions that take place within microbial cells are highly diverse
There are 2 key “ingredients” in this diverse collection of recipes
Carbon-for precursors and building blocks
Energy-to make things work

2. Introduction-Overview and Definitions Carbon and Metabolic Diversity
Energy Pathways: Electron Transfers, ATP Production
Other Catabolic Diversity

3. Introduction-Overview and Definitions
Metabolism
The sum total of all of the chemical reactions that occur in a cell
Catabolic reactions (catabolism)
Energy-releasing metabolic reactions, typically break down large molecules to precursors and building blocks
Anabolic reactions (anabolism)
Biosynthetic metabolic reactions that use the precursors and the building blocks

4. Broad Overview of Metabolism
There are only a few key precursor molecules (but lots of ways
to get them or make them)
Energy sources vary: light, chemical bonds etc.

5. Carbon dioxide etc.
But prokaryotes will not make something by de novo synthesis if they can import it instead

6. Classification based on Energy/Carbon Source
Microorganisms have a variety of ways to conduct their metabolism
Grouped into energy source classes
Chemotrophs use chemical energy
Lithotrophs use inorganic compounds
Organotrophs use carbon compounds
Phototrophs use light energy
Oxygenic release oxygen as waste product
Anoxygenic release some other waste product

7. Classification based on Energy/Carbon Source
Microorganisms have a variety of ways to conduct their metabolism
Grouped into carbon source classes
Heterotrophs rely on reduced carbon in the environment
Autotrophs reduce aka “fix” their own CO2

8. Phototrophic autotrophs (photoautotrophs) are familiar
Autotrophs fix carbon but they may be chemotrophs or phototrophs with respect to energy source
Phototrophic autotrophs (photoautotrophs) are familiar
Cyanobacteria (Sec.14.3)
Photosynthesize using chlorophyll a
Fix CO2 to carbohydrate using Calvin Cycle
Chemotrophic autotrophs (chemoautotrophs) are less familiar
Methanogens (Sec.13.20) = Archaea; sediments, animals
Convert CO2 to CH4 with unusual enzymes for energy
Utilize methanol or acetate from CH4 for carbon

9. Chemotrophic heterotrophs (chemoheterotrophs) are very common
Heterotrophs acquire reduced carbon from the environment but may be chemotrophs or phototrophs with respect to energy source
Chemotrophic heterotrophs (chemoheterotrophs) are very common
Phototrophic heterotrophs (photoheterotrophs) also exist
Heliobacter (Sec. 14.8) a gram + rod
Carries out photosynthesis using bacteriochlorophyll g
Relies on pyruvate, lactate, butyrate, acetate for carbon