microbial metabolism. a. basic concepts definitions metabolism: the processes of catabolism and...
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Microbial Metabolism
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
What are nutrients that bacteria want?
C Sugar, Lipid Energy, Biosynthesis
N Protein Biosynthesis
O Air Energy
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 respiration– Most efficient way to extract energy from
glucose.– Process: Glycolysis
Kreb Cycle
Electron transport chain– Glycolysis: Several glycolytic pathways– The most common one:
glucose-----> pyruvic acid + 2 NADH + 2ATP
B. 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
Formation of intermediates of the Embden– Meyerhof–Parnas (EMP) and Entner–Doudoroff (ED) pathway
from carbohydrates other than glucose
BIOCHEMICAL REACTIONS OF RESPIRATION
Carbohydrate Metabolism
4. TCA cycle
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.
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
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