Transcript metabole

Metabolism of Bacteria
By
Ms.Patchanee Yasurin
471-9893
Faculty of Biotechnology
Assumption Univerity
Why do we must know the
metabolism of bacteria ?
Because we want to know how to inhibit
or stop bacteria growth and want to control
their metabolism to prolong shelf-life of
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
What are nutrients that bacteria want?
C
N
O
Sugar, Lipid
Protein
Air
Energy, Biosynthesis
Biosynthesis
Energy
Biochemical Components of Cells
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Water: 80 % of wet weight
Dry weight
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Protein 40-70 %
Nucleic acid 13-34%
Lipid 10-15 %
Also monomers, intermediates and
inorganic ions
Nutrient
requirements
Concepts:
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.
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

macronutrients: required in large amounts
Micronutrients and growth
factors

Micronutrients: Metals and metalloids

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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
micronutrients:
• required in lesser,
sometimes trace
amounts
• not every element is
required by all cells
growth factors: organic compounds required in small amounts
• not every growth factor is required by all cells
A. Basic Concepts

Definitions

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Metabolism: The processes of catabolism and
anabolism
Catabolism: The processes by which a living
organism obtains its energy and raw materials
from nutrients
Anabolism: The processes by which energy
and raw materials are used to build
macromolecules and cellular structures
(biosynthesis)
Overview of cell metabolism
Breakdown
Proteins to Amino Acids, Starch to Glucose
Synthesis
Amino Acids to Proteins, Glucose to Starch
Bacterial Metabolism ☺
Exoenzymes: Bacteria cannot
transport large polymers into the cell.
They must break them down into
basic subunits for transport 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).
Energy Generating Patterns
–
–
After Sugars are made or obtained, they are
the energy source of life.
Breakdown of sugar(catabolism) different
ways:
• Aerobic respiration
• Anaerobic respiration
• Fermentation
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
Glycolysis: Several glycolytic pathways
The most common one:
glucose-----> pyruvic acid + 2 NADH +
2ATP
Glycolysis
Glycolytic Pathways

4 major glycolytic pathways found in different
bacteria:

Embden-Meyerhoff-Parnas pathway
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Hexose monophosphate pathway
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Also found in most organisms
Responsible for synthesis of pentose sugars used in
nucleotide synthesis
Entner-Doudoroff pathway


“Classic” glycolysis
Found in almost all organisms
Found in Pseudomonas and related genera
Phosphoketolase pathway

Found in Bifidobacterium and Leuconostoc
Carbohydrate Metabolism
1. Embden–Meyerhof–Parnas (EMP) pathway, glycolysis
cyclic “pathway”
Pyruvic acid is first acted on by an NZ and a coenzyme (COA). The end product
is Acetyl-Coa and a CO2 molecule.
Remember this occurs twice for each glucose molecule. (One glucose is split into
two pyruvic acid molecules.)
TCA Cycle
(Krebs)
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.

Carbohydrates,
fats, and proteins
can all be
catabolized
through the same
pathways.
Fig. 9.19
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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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 acids – OH SO MUCH
MORE!!! Take biochem.
Lipid Metabolism

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Lipids are essential to the structure and function of
membranes
Lipids also function as energy reserves, which can
be mobilized as sources of carbon
90% of this lipid is “triacyglycerol”
lipase
triacyglycerol
glycerol + 3 fatty acids
The major fatty acid metabolism is “β-oxidation”
Lipid Metabolism
β-oxidation of fatty acid
Lipid Metabolism
Glycerol Metabolism
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 or Krebs to make ATP
Nitrogen Metabolism

Nitrogen is an essential element of
biological molecules, such as amino acids,
nucleotides, proteins, and DNA

Bacteria vary widely in their ability to
utilize various sources of nitrogen for
synthesis of proteins
General view of nitrogen metabolism
Amino acid degradation
Pathways Involved in Nitrogen Utilization
1. Protein Digestion – by proteinase and peptidase
2. Oxidative Deamination
3. Reductive Deamination
4. Decarboxylation
5. Transamination Reactions
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.
Chemoautotroph:
Bacteria
Electron
donor
Electron
acceptor
Products
Alcaligens and
Pseudomonas sp.
H2
O2
H2O
Nitrobacter
NO2NH4+
H2
S0. H2S
O2
O2
SO4 2NO3-
NO3- , H2O
NO2- , H2O
H2O. H2S
SO4 2- , N2
Fe2+
O2
Fe3+ , H2O
Nitrosomonas
Desulfovibrio
Thiobacillus denitrificans
Thiobacillus ferrooxidans
Nitrifying bacteria
2 NH4+ + 3 O2
2 NO2- + 2 H2O + 4 H+ + 132 Kcal
C. Fermentation

Features of fermentation pathways

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Pyruvic acid is reduced to form reduced
organic acids or alcohols.
The final electron acceptor is a reduced
derivative of pyruvic acid
NADH is oxidized to form NAD: Essential
for continued operation of the glycolytic
pathways.
O2 is not required.
No additional ATP are made.
Gasses (CO2 and/or H2) may be released
Fermentation
Glycosis:
Glucose ----->2 Pyruvate + 2ATP + 2NADH

Fermentation pathways
a. 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.
Fig. 9.18
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Re-Dox Reactions
Central
Metabolism
Glycolysis
Fermentation Products
Nutrition
Table 27.1
Alternative energy generating
patterns(3)
Alternative energy generating
patterns(4)
Energy/carbon classes of organisms
Fig. 5-12
Overview of Metabolism
Electron Transport Chain
Electron Flow
and Energy
Trapping
Microbiology chapters 7 - 8 part 2
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? ____
ATP – Adenosine triphosphate, universal cellular energy
Cyclically made and energy is stored and then broken down and the
energy is released
ATP – Adenosine 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
Note: ATP is a ribonucleotide, it has ribose, a nitogenous base
(adenine), and phosphate. The high energy bond of the terminal of
the three phosphates is the one cyclically broken and regenerated.
Sugars like glucose can be broken down in a catabolic pathway
controlled 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
Note: ATP is a ribonucleotide, it has ribose, a nitogenous base
(adenine), and phosphate. The high energy bond of the terminal of
the three phosphates is the one cyclically broken and regenerated.
Sugars like glucose can be broken down in a catabolic pathway
controlled 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
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 CO2 molecule.
Remember this occurs twice for each glucose molecule. (One glucose is split into
two pyruvic acid molecules.)
Krebs cycle (TCA, Citric acid cycle) Aerobic stage, Occurs in the
fluid of the Matrix

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 CO2 molecule.

Remember this occurs twice for each
glucose molecule. (One glucose is split
into two pyruvic acid molecules.)
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.
Microbiology chapters 7 - 8 part 2
The electrons are passed down the chain and end up being added to 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, flow
through ATP synthase related channel, energy is harvested in high energy bonds
of ATP. Enough to generate 34 more ATP.
Carbohydrate Metabolism
2. Entner–Doudoroff (ED) pathway
Carbohydrate Metabolism
3. Pentose phosphate (PP) pathway
Formation of intermediates of the Embden– Meyerhof–Parnas
(EMP) and Entner–Doudoroff (ED) pathway from carbohydrates
other than glucose
Table 1: Distribution of Embden–Meyerhof–Parnas
(EMP), Entner–Doudoroff (ED), and pentose phosphate
(PP) pathway in bacteria
Organism
Pseudomonas aeruginosa
Enterococcus faecalis
(Streptococcus)
Salmonella typhimurium
Bacillus subtilis
Escherichia coli
Yersinia pseudotuberculosis
Remark:
+ = Present;
– = not present.
i = inducible
EMP
+
+
+
+
+
ED
+i
+i
PP
+
+i
+i
+i
+
+
-