Chapter 5: Microbial
Metabolism
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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
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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• Large 3-D globular
molecule
• Composed of two parts
1. Protein portion
(apoenzyme)
Enzymes
– 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)
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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)
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
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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”
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Carbohydrate Catabolism
•
Most microorganisms use
carbon as primary energy
source
• Oxidation of glucose
1. Cellular Respiration

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

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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)
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Lactic Acid Fermentation
•Streptococcus
• Lactobacillus
• Bacillus
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Photosynthesis
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• Conversion of light energy into chemical energy
• Chemical energy then used to convert CO2 into
sugars (carbon fixation)
• Cyanobacteria
REVIEW
• Cellular Respiration
– Aerobic
– Carbon
• Fermentation
– Anaerobic
– Carbon
• Photosynthesis
– Carbon Fixation
– Light energy
Classifying BacteriaNutritional 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
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Found in sulfidecontaining freshwater
habitats
(photosynthesis)
Green and Purple
Bacteria - use sulfur
or hydrogen gas to
reduce CO2 and
make organic
compounds
ChlorobiumGreen Bacteria
found in hot
springs, cold lakes
and sediments
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PHOTOHETEROTROPHS
Energy: Light
Carbon: organic compounds
Examples:
Green nonsulfur bacteria
Chloroflexus
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(found in hot springs, lakes,
hyersaline environments)
Purple nonsulfur bacteria
Rhodopseudomonas
(found in soil and marine
environments)
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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,
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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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•
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