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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 enzymesand coupled together

Metabolism: Overview

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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

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Enzymes• Large 3-D globular molecule

• Composed of two parts1. 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: Steps in a Reaction

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Enzymes: Overview

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HOW DO YOU

CONTROL GROWTH OF BACTERIA??

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CONTROL THEIR

ENZYMES!(Using inhibitors)

InhibitorsCompetitive 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

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InhibitorsNoncompetitive 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

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Carbohydrate Catabolism• Most microorganisms use

carbon as primary energy source

• Oxidation of glucose1. Cellular Respiration

Glycolysis Krebs cycle Electron Transport Chain Lots of energy made

2. Fermentation Glycolysis Products: Alcohol or lactic acid Little energy made

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Fermentation• Releases energy

from sugars or other organic molecules

• Does not require oxygen

• Produces only a small amount of ATP

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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

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REVIEW

• Cellular Respiration– Aerobic– Carbon

• Fermentation– Anaerobic– Carbon

• Photosynthesis– Carbon Fixation– Light energy

Classifying Bacteria-Nutritional Pattern

HOW DO THEY GET

ENERGY?Phototrophs: use light as

primary energy sourceChemotrophs: use

reactions of inorganic or organic compounds for energy

HOW DO THEY GET CARBON?Autotrophs: CO2 as principle

carbon sourceHeterotrophs: organic

carbon source

PHOTOAUTOTROPHSEnergy: lightCarbon: CO2

Examples: cyanobacteria(photosynthesis)

Green and Purple Bacteria - use sulfur or hydrogen gas to reduce CO2 and make organic compounds

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Chromatium -Purple BacteriaFound in sulfide-containing freshwaterhabitats

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Chlorobium- Green Bacteriafound in hotsprings, cold lakesand sediments

PHOTOHETEROTROPHS

Energy: LightCarbon: organic compoundsExamples:Green nonsulfur bacteria

Chloroflexus (found in hot springs, lakes,

hyersaline environments)

Purple nonsulfur bacteriaRhodopseudomonas

(found in soil and marine environments)

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CHEMOAUTOTROPHS

Energy: inorganic compoundsEx: H2S, S, NH3, H2, CO

Carbon: CO2

-fix CO2

Example:Beggiatoa - use H2S, found in soil,

sulfur springs, mud layers of lakes,

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CHEMOHETEROTROPHS

Energy: organic compoundsEx: 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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• http://people.eku.edu/ritchisong/RITCHISO/energyflowchart.jpg

• http://www.hepafilters.com/images/microbes.jpg• http://www.bio12.com/ch6/RemedialEnzymes_file

s/image007.jpg• http://classes.midlandstech.edu/carterp/Courses/bi

o225/chap05/Slide13.GIF