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Metabolism of Bacteria
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Why do we must know the metabolism of
bacteria ?Because we want to know how to inhibit or stopbacteria
growth and want to control their metabolism to prolong
shelf-lifeof food products.
What is Metabolism?
The Greek metabole, meaning change
It is the totality of an organism's chemical processes to
maintain life.
- Catabolism
- Anabolism
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What are nutrients that bacteria want?
C Sugar, Lipid Energy, Biosynthesis
N Protein Biosynthesis
O Air Energy
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Biochemical Components of Cells Water: 80 % of wet weight
Dry weight
Protein 40-70 %
Nucleic acid 13-34%
Lipid 10-15 %
Also monomers, intermediates and
inorganic ions
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Microorganisms require about ten elements in large
quantities, because they are used to construct
carbohydrates, lipids, proteins, and nucleic acids.
Several other elements are needed in very small
amounts and are parts of enzymes and cofactors.
Concepts:
Nutrientrequirements
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Macronutrients Cells make proteins, nucleic acids and
lipids
Macronutrients
macromolecules, metabolism
C, H, O, N, S, P, K, Mg, Fe
Sources
Organic compounds
Inorganic salts
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Micronutrients and growth
factors Micronutrients: Metals and metalloids
Elements needed in trace quantities
Generally not necessary to add to medium Deficiencies can arise when medium constituents
are very pure
Growth factors: organic requirements
Vitamins, amino acids, purines, pyrimidines,
acetate
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micronutrients: required in lesser,
sometimes trace
amounts
not every element is
required by all cells
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growth factors:organic compounds required in small amountsnot every growth factor is required by all cells
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A. Basic Concepts Definitions
Metabolism: The processes of catabolism and
anabolism Catabolism: The processes by which a living
organism obtains its energy and raw materialsfrom nutrients
Anabolism: The processes by which energyand raw materials are used to buildmacromolecules and cellular structures(biosynthesis)
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Overview of cell metabolism
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Breakdown
Proteins to Amino Acids, Starch to Glucose
SynthesisAmino Acids to Proteins, Glucose to Starch
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Bacterial Metabolism
Exoenzymes: Bacteria cannot transport
large polymers into the cell. They must
break them down into basic subunits fortransport into the cell. Bacteria therefore
elaborate extracellular enzymes for the
degradation of carbohydrates to sugars
(carbohydrases), proteins to amino acids
(proteases), and lipids to fatty acids
(Lipases).
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After Sugars are made or obtained, they are
the energy source of life.
Breakdown of sugar(catabolism) different
ways:
Aerobic respiration Anaerobic respiration
Fermentation
Energy Generating Patterns
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Aerobic respiration
Glucose is a hexose, monosaccharide, C6H12O6 It is systematically broken down through
three related pathways to Carbon dioxide
(CO2) and Water (H2O) Process:
1. Glycolysis (in cytoplasm)
2. Kreb Cycle (in mitochondria)
3. Electron transport chain
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Glycolysis: Several glycolytic pathways
The most common one:
glucose----->pyruvic acid + 2 NADH + 2ATP
Fi 8 Gl l ti P th
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Section 8 1: Glycolysis
Figure 8.3 Glycolytic Pathway
From McKee and McKee, Biochemistry, 5th Edition, 2011 Oxford University Press
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Glycolysis
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Glycolytic Pathways
4 major glycolytic pathways found in differentbacteria:
Embden-Meyerhoff-Parnas pathway
Classic glycolysis
Found in almost all organisms Hexose monophosphate pathway
Also found in most organisms
Responsible for synthesis of pentose sugars used in
nucleotide synthesis
Entner-Doudoroff pathway
Found in Pseudomonasand related genera
Phosphoketolase pathway
Found in Bifidobacteriumand Leuconostoc
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cyclic pathwayPyruvic acid is first acted on by an NZ and a coenzyme (COA).
The end product is Acetyl-Coa and a CO2molecule.
Remember this occurs twice for each glucose molecule. (One
glucose is split into two pyruvic acid molecules.)
TCA
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TCA
Cycle
(Krebs)
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Return to Krebs and show how it works with electron
transport chain. Note how glycolysis and Krebs are
working together. Note that each produces reduced
carriers that need to be processed.
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Carbohydrates,
fats, and
proteins can all
be catabolized
through the
same pathways.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 9.19
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Lipid Metabolism Lipids are essential to the structure and function of membranes
Lipids also function as energy reserves, which can be mobilized assources of carbon
90% of this lipid is triacyglycerol
triacyglycerol lipase glycerol + 3 fatty acids
The major fatty acid metabolism is -oxidation
Lipids are catabolized to Glyerol and Fatty acids
Glycerol easily enters glycolysis and Krebs just like pyruvate
Fatty acids are chopped into 2 or 3 acid fragments that are
broken downt to carbondioxide
Even nucleic acidsOH SO MUCH MORE!!! Take
biochem.
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Lipid Metabolism
-oxidation of fatty acid
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Lipid Metabolism
Glycerol Metabolism
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Other fuels
Proteins: digested to amino acids Amino acids are :
deaminated : amino group removed, the
reulting acid can be further metabolized,more ATP
decarboxylated: carboxyl group removed,
the end products then enter glycolysis orKrebs to make ATP
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Nitrogen Metabolism
Nitrogenis an essential element ofbiological molecules, such as amino acids,
nucleotides, proteins, and DNA
Bacteria vary widely in their ability toutilize various sources of nitrogen for
synthesis of proteins
G l i f it t b li
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General view of nitrogen metabolism
i id d d i
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Amino acid degradation
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Pathways Involved in Nitrogen Utilization
1. Protein Digestionby proteinase and peptidase
2. Oxidative Deamination
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3. Reductive Deamination
4. Decarboxylation
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5. Transamination Reactions
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Anaerobic respiration
Final electron acceptor : never be O2
Sulfate reducer: final electron acceptor is sodium
sulfate (Na2 SO4)
Methane reducer: final electron acceptor is CO2
Nitrate reducer : final electroon acceptor is
sodium nitrate (NaNO3)
O2/H2O coupling is the most oxidizing, more energy
in aerobic respiration.
Therefore, anaerobic is less energy efficient.
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Chemoautotroph:
Nitrifying bacteria
2 NH4++ 3 O2 2 NO2- + 2 H2O + 4 H++ 132
Kcal
Bacteria Electron
donor
Electron
acceptor
Products
Alcaligens and
Pseudomonas sp.H2 O2 H2O
Nitrobacter NO2- O2 NO3
-, H2O
Nitrosomonas NH4+ O2 NO2- , H2ODesulfovibrio H2 SO4 2- H2O. H2SThiobacillus denitrificans S0. H2S NO3
- SO4 2- , N2
Thiobacillus ferrooxidans Fe2+ O2 Fe3+ , H2O
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C. Fermentation
Features of fermentation pathways Pyruvic acid is reduced to form reduced
organic acids or alcohols.
The final electron acceptor is a reducedderivative of pyruvic acid
NADH is oxidized to form NAD: Essentialfor continued operation of the glycolytic
pathways.
O2is not required.
No additional ATP are made.
Gasses (CO2and/or H2) may be released
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Fermentation Glycosis:
Glucose ----->2 Pyruvate + 2ATP + 2NADH
Fermentation pathwaysa. Homolactic acid F.
P.A -----> Lactic Acid
eg. Streptococci, Lactobacilli
b.Alcoholic F.
P.A -----> Ethyl alcohol
eg. yeast
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Some organisms (facultative anaerobes),
including yeast and many bacteria, can survive
using either fermentation or respiration. For facultative anaerobes,
pyruvate is a fork in the
metabolic road that leads
to two alternative routes.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 9.18
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Re Dox Reactions
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Re-Dox Reactions
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Central
Metabolism
Fermentation Products
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Fermentation Products
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Nutrition
Table 27.1
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Alternative energy generating
patterns(3)
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Alternative energy generating
patterns(4)
Energy/carbon classes of organisms
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Energy/carbon classes of organisms
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Overview of Metabolism
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Overview of Metabolism
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Electron Transport Chain
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p
Electron Flow
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Electron Flow
and Energy
Trapping
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Microbiology chapters 7 - 8 part 2
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gy p p
Glycolysis: Anaerobic, no oxygen required,
linear NZ pathway Begins with ______
End products _________
How much ATP? _______
How many carrier molecules? ____
Name the carrier molecule. ____
Where in the cell? _______
What happens after if the organism
Is an aerobe? _____
Facultative? ______ Strict anaerobe? ______
Aerobe deprived of oxygen? ____
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ATPAdenosine triphosphate, universal cellular energy
Cyclically made and energy is stored and then broken down and the
energy is released
Microbiology chapters 7 8 part 2
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Microbiology chapters 7 - 8 part 2
Note: ATP is a ribonucleotide, it has ribose, a nitogenous base
(adenine), and phosphate. The high energy bond of the terminalof the three phosphates is the one cyclically broken and
regenerated.
Sugars like glucose can be broken down in a catabolic pathwaycontrolled by many cellular enzymes. Some of the energy
released by the breaking of covalent bonds is harvested and
stored in the energy bonds of ATP.
Most any biomolecule can be used for energy; we will focus on
the catabolism of glucose (a monosaccharide) and later show
how the others are involved (lipids, AA, etc)
Microbiology chapters 7 - 8 part 2
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gy p p
This is a cyclic pathway
Pyruvic acid is first acted on by an NZ and a coenzyme (COA).
The end product is Acetyl-Coa and a CO2molecule.
Remember this occurs twice for each glucose molecule. (One
glucose is split into two pyruvic acid molecules.)
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Krebs cycle (TCA, Citric acid cycle) Aerobic stage, Occurs in the
fluid of the Matrix
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This is a cyclic pathway Pyruvic acid is
first acted on by an NZ and a coenzyme
(COA). The end product is Acetyl-Coa
and a CO2molecule.
Remember this occurs twice for each
glucose molecule. (One glucose is splitinto two pyruvic acid molecules.)
Return to Krebs and show how it works with electron transport
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Return to Krebs and show how it works with electron transport
chain. Note how glycolysis and Krebs are working together. Note
that each produces reduced carriers that need to be processed.
The electrons are passed down the chain and end up being added to
Th H d i (H+) i d t ( t ) d
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oxygen. The Hydrogen ion (H+) is pumped out (proton pump) and
flows back in at special sites to be added to the Oxygen and electron
to form Water. Energy is conserved (harvested; stored) in the bonds
of ATP
Theory of Chemiosmosis: Proton pump, increased H+ ion
concentration flo thro gh ATP s nthase related channel energ
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concentration, flow through ATP synthase related channel, energy
is harvested in high energy bonds of ATP. Enough to generate 34
more ATP.
Carbohydrate Metabolism
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Carbohydrate Metabolism
2. EntnerDoudoroff (ED) pathway
Carbohydrate Metabolism
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Carbohydrate Metabolism
3. Pentose phosphate (PP) pathway
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Formation of intermediates of the EmbdenMeyerhofParnas
(EMP) and EntnerDoudoroff (ED) pathway from carbohydrates
other than glucose
Table 1:Distribution of EmbdenMeyerhofParnas
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y(EMP), EntnerDoudoroff (ED), and pentose phosphate(PP) pathway in bacteria
Organism EMP ED PP
Pseudomonas aeruginosa - +i -
Enterococcus faecalis + +i +
(Streptococcus)
Salmonella typhimurium + +i +Bacillus subtilis + - -
Escherichia coli + +i +
Yersinia pseudotuberculosis + +i -
Remark: + = Present;
= not present.
i = inducible