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