Chapter 5: Microbial Metabolism

METABOLISM Sum of all chemical rxn’s within a living organism Release energy Require energy

CATABOLIC REACTION (breakdown) Breakdown of complex organic compounds into simpler ones Generally hydrolytic reactions (water used to break bonds) Exergonic (produce more energy than consume) Provide building blocks for anabolic rxns and energy needed to drive anabolic rxns ANABOLIC REACTIONS (build) Building of complex organic molecules from simpler ones Generally dehydration synthesis Endergonic (consume more energy than produce) ATP <=> ADP + Pi + energy Rxn’s all determined by enzymes and coupled together

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But reactions happen very SLOWLY by themselves But reactions happen very SLOWLY by themselves....to make reactions go FASTER we need.........

ENZYMES !

Enzymes Biological catalysts Each act on a specific substance (substrate) Has active site for substrate to bind to “loading dock” Each catalyzes only one reaction Sensitive to temperature, pH, concentration Can become denatured All end in -ase

Enzymes Large 3-D globular molecule Composed of two parts 1. Protein portion (apoenzyme) Inactive if alone 2. Nonprotein component (cofactor) Ions of iron, zinc, magnesium or calcium If organic = coenzyme Together with the apoenzyme and cofactor = active enzyme (holoenzyme) Enzymes

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HOW DO YOU CONTROL GROWTH OF BACTERIA??

CONTROL THEIR ENZYMES! (Using inhibitors)

Inhibitors Competitive Inhibitors Fill the active site of an enzyme and compete with the normal substrate for the active site Similar shape and chemical structure Does not produce products Example: Sulfa drug Animation: CD

Inhibitors Noncompetitive Inhibitors Do not compete with the substrate; instead interact with another part of the enzyme Binds and causes the active site to change its shape, making it nonfunctional Allosteric inhibition “other space” Animation: CD

Carbohydrate Catabolism Most microorganisms use carbon as primary energy source Oxidation of glucose Cellular Respiration Glycolysis Krebs cycle Electron Transport Chain Lots of energy made Fermentation Products: Alcohol or lactic acid Little energy made

Fermentation Releases energy from sugars or other organic molecules Does not require oxygen Produces only a small amount of ATP

Alcohol Fermentation: Saccharomyces (yeast) Lactic Acid Fermentation Streptococcus Lactobacillus Bacillus

Photosynthesis

Conversion of light energy into chemical energy Chemical energy then used to convert CO2 into sugars (carbon fixation) Cyanobacteria

REVIEW Cellular Respiration Fermentation Photosynthesis Aerobic Carbon Anaerobic Photosynthesis Carbon Fixation Light energy

Classifying Bacteria- Nutritional Pattern HOW DO THEY GET ENERGY? Phototrophs: use light as primary energy source Chemotrophs: use reactions of inorganic or organic compounds for energy HOW DO THEY GET CARBON? Autotrophs: CO2 as principle carbon source Heterotrophs: organic carbon source

PHOTOAUTOTROPHS Energy: light Carbon: CO2 Examples: cyanobacteria Chromatium - Purple Bacteria Found in sulfide- containing freshwater habitats Energy: light Carbon: CO2 Examples: cyanobacteria (photosynthesis) Green and Purple Bacteria - use sulfur or hydrogen gas to reduce CO2 and make organic compounds Chlorobium- Green Bacteria found in hot springs, cold lakes and sediments

PHOTOHETEROTROPHS Energy: Light Carbon: organic compounds Examples: Green nonsulfur bacteria Chloroflexus (found in hot springs, lakes, hyersaline environments) Purple nonsulfur bacteria Rhodopseudomonas (found in soil and marine environments)

CHEMOAUTOTROPHS Energy: inorganic compounds Ex: H2S, S, NH3, H2, CO Carbon: CO2 -fix CO2 Example: Beggiatoa - use H2S, found in soil, sulfur springs, mud layers of lakes,

CHEMOHETEROTROPHS Energy: organic compounds Ex: glucose *use the electrons from H-atoms as energy source Carbon: organic compound *Hard to distinguish-use the same compound Example: Streptococcus pneumonia - fermentation

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