sir,SEIF CUHAS MWANZA

1. BACTERIAL METABOLISM

2. 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
 usually release energy that is used to drive
chemical reactions
 Anabolism:The processes by which energy and
raw materials are used to build macromolecules
and cellular structures (biosynthesis)
 The energy of catabolic reactions is used to
drive anabolic reactions

4. Overview of cell metabolism

5. What are nutrients that bacteria want?
C Sugar, Lipid Energy, Biosynthesis
N Protein Biosynthesis
O Air Energy

6. Breakdown
Proteins to Amino Acids, Starch to Glucose
Synthesis
Amino Acids to Proteins, Glucose to Starch

7. Bacterial Metabolism
 Exoenzymes: Bacteria cannot transport large
polymers into the cell
 They must break them down into basic subunits for
transport into the cell
 therefore they elaborate extracellular enzymes for
the degradation of;
 carbohydrates to sugars (carbohydrases)
 proteins to amino acids (proteases)
 and lipids to fatty acids (Lipases)

8. – 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

9. Aerobic respiration
– Most efficient way to extract energy from glucose
– Process: Glycolysis
Krebs Cycle
Electron transport chain
– Glycolysis: Several glycolytic pathways
– The most common one:
glucose-----> pyruvic acid + 2 NADH + 2ATP

10. 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

15. 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 electron acceptor is sodium
nitrate (NaNO3)
 O2/H2O coupling is the most oxidizing, more energy in
aerobic respiration
 Therefore, anaerobic is less energy efficient.

16. Fermentation
 is a metabolic process process that
converts sugar to acids, gases and/or alcohol
 It occurs in yeast and bacteria, but also in oxygen-
starved muscle cells
 as in the case of lactic acid fermentation
 Fermentation takes place in the lack of oxygen
 when the electron transport chain is unusable and
becomes the cell’s primary means of ATP (energy)
production

17. 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

18. Fermentation
 Glycosis:
Glucose ----->2 Pyruvate + 2ATP + 2NADH
 Fermentation pathways
a. Homolactic acid F.
P.A -----> Lactic Acid
e.g.. Streptococci, Lactobacilli
b.Alcoholic F.
P.A -----> Ethyl alcohol
e.g.yeast

19. Examples of fermentation pathways
a) Lactic acid fermentation
• Found in many bacteria; e.g. Streptococcus spp., Lactobacillus
acidophilus
b) Mixed acid fermentation
• e.g. Escherichia coli
• basis of the methyl red test
c) 2,3-Butanediol fermentation
• e.g. Enterobacter aerogenes
• basis of theVoges-Proskauer reaction

23. Microbial nutrition
 Aspect of microbial physiology that deals with supply
of monomers that cells need for growth
 Nutrients requirement differ because organisms differ
 Macronutrients and Micronutrients

24. Carbon
 All cells require carbon
 On a dry weight basis typical cell is about 50% carbon
 Major element in classes of macromolecules
 Bacterial can assimilate different organic carbon
compounds
 (Amino acids, sugars, organic acids, etc)

25. Nitrogen
 Second abundant element
 12% of dry weight
 Important in proteins, nucleic acids
 In environment N is available in NH3 or NO3
 Most bacteria are capable of using NH3 as sole nitrogen
source
 Nitrogen gas can be used with certain bacteria (Nitrogen
fixing bacteria)

26. Other Macronutrients
 Phosphorus:
 organic
 inorganic phosphates
 Structural role in nucleic acids and phospholipids
 Sulfur:
 Cysteine
 Methionine
 Sulfur is from inorganic sources either sulfate and
sulfide
 Potassium, Magnesium, Calcium

27. Micronutrients
 Boron
 Chromium
 Cobalt
 Copper
 Iron: cellular respiration component of cytochromes
 Manganese
 Molybdenum
 Zinc

28. Chemical supplied in Culture media
 Glucose, malate, acetate,pyruvate, amino acids, yeast
extract, citrate, peptone
 H2O, organic compounds
 NH4Cl, (NH4)SO4, NaCl, MgCl, MgSO4
 FeCl3

29. Nutrition
Table 27.1