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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 Sugar, Lipid Energy, Biosynthesis
N Protein Biosynthesis
O Air Energy
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
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:
Nutrient requirements
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
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
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
BreakdownProteins to Amino Acids, Starch to Glucose
SynthesisAmino 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).
– 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
Aerobic respirationGlucose 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
“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 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.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 9.19
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 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”
triacyglycerol lipase 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:
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
- , H2ONitrosomonas NH4
+ O2 NO2- , H2O
Desulfovibrio H2 SO4 2- H2O. H2S
Thiobacillus denitrificans S0. H2S NO3- SO4
2- , N2
Thiobacillus ferrooxidans Fe2+ O2 Fe3+ , H2O
C. Fermentation Features of fermentation pathways
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 pathwaysa. Homolactic acid F.
P.A -----> Lactic Acideg. Streptococci, Lactobacilli
b.Alcoholic F.P.A -----> Ethyl alcoholeg. yeast
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 Cummings
Fig. 9.18
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 pathwayBegins 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 2The 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 EMP ED PPPseudomonas aeruginosa - +i -Enterococcus faecalis + +i +(Streptococcus)Salmonella typhimurium + +i +Bacillus subtilis + - -Escherichia coli + +i +Yersinia pseudotuberculosis+ +i -
Remark: + = Present; – = not present. i = inducible
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