Chapter 5
Microbial Nutrition and Culture
Siti Sarah Jumali (ext 2123)
Room 3/14
sarah_jumali84@hotmail.com
Groups of bugs based on energy
capture and carbon source
• AUTOTROPHY: Use carbon
dioxide to synthesize organic
molecules
• Two types:
1. Photoautotrophs: obtain energy
from light
2. Chemoautotrophs: obtain energy
from oxidizing simple inorganic
substance
Groups of bugs based on energy
capture and carbon source cont’d
• HETEROTROPHY: Get carbon dioxide from
ready made organic molecules
• Two types:
1. Photoheterotrophs: obtain chemical energy
from light
2. Chemoheterotrophs: obtain energy from
breaking down ready-made organic
compounds
The main types of energy capturing Metabolism
All
microorganisms
Inorganic CO2 = carbon source AUTOTROPH
(Self feeders)
Making own food by reducing CO2
Photoautotrophs
Chemoautotrophs
Organic compound = carbon source
HETEROTROPH
Using ready-made organic molecules for food
Photoheterotrophs
Chemoheterotrophs
Examples of Energy Source
Type
Energy Source
Carbon Source
Examples
Photolithotrophs
Light
CO2
Algae,Purple sulphur
bacteri,green sulphur
bacteria
Photoorganotrophs
Light
Organic Compounds
Purple non sulphur
bacteria
Chemolithotrophs
Oxidation of
inorganic compounds
Chemoorganotrophs
Oxidation of organic
compounds
Nitrifying
bacteria,iron
bacteria,H2 bacteria
Organic Compounds
Most bacteria,
fungi,protozoa
Photosynthesis and Respiration
Metabolism
• The sum of all chemical processes carried out by living
organisms
• Anabolism: rxn that requires energy in order to
synthesize complex molecules from the simpler ones
- (use energy and building blocks to build large
molecules)
• Catabolism: rxn that releases energy by breaking
complex molecules into simpler ones which can be
reused as building blocks
- (provides energy and building blocks for anabolism)
Metabolism: The sum of catabolism
and anabolism
Catabolism
Larger
molecules
Smaller
Molecules
Anabolism
Energy
Metabolic Pathway
• Glycolisis, fermentation, aerobic respiration and
photosynthesis each consists of a series of chemical
reaction
• The product of one reaction serves as the substrate for the
next: ABCD
• Such chain of reactions is called a metabolic pathway:
- Anabolic pathways make the complex molecules that
form structure of cells, enzymes and molecules that
control cells
- Catabolic pathways capture energy in a form a cell can
use
Oxidation-Reduction Reactions
• All catabolic reactions involve electron
transfer which is directly related to oxidation
and reduction (redox potential)
• Redox reaction: An oxidation reaction paired
with a reduction reaction
- Oxidation: the loss of removal of electrons
-Reduction: the gain of electrons
Oxidation-Reduction Reactions
Representative Biological Oxidations
In biological systems, the electrons are often
associated with hydrogen atoms. Biological
oxidations are often dehydrogenation.
Acronyms for oxidation and reduction:
•Oxidation Is Losing Electrons, Reduction Is Gaining Electrons: OIL RIG
•Losing Electrons Oxidation, Gaining Electrons Reduction: LEO the lion. GER! or LEO
says GER
•Electron Loss Means Oxidation: ELMO
Metabolic Pathways of Energy Production
13
Metabolic Pathways of Energy
Production
(b)
Energy Transfer by Carrier Molecules
• Carrier molecules such as Cytochrome (cyt) and
some coenzymes carry energy in the form of
electrons in many biochemical reactions
• Coenzymes such as FAD carry whole hydrogen
atoms (electrons together with protons); NAD
carries one hydrogen atom and one “naked”
electron
• When co-enzymes are reduced, they increase in
energy, when they are oxidized, they decrease in
energy.
Energy Generation of ATP
• ATP is generated by the phosphorylation of
ADP
Energy
ADP + Pi + Energy
ATP
• In cells, energy is provided by the hydrolysis of
ATP
ATP
ADP + Pi + Energy
Energy
Generation of ATP
1. Substrate level Phosphorylation: Energy from the
transfer of a high energy PO4 to ADP generates ATP
C-C-C-P + ADP C-C-C + ATP
2. Oxidative Phosphorylation: Energy relseased from
transfer of electrons (oxidation) of one compound to
another (reduction) is used to generate Atp in the
electron transport chain
3. Photophosporylation: Light causes chlorophyll to give
up electrons. Energy released from transfer of
electrons (oxidation) of chlorophyll trough a system of
carrier molecules is used to generate ATP
Overview of Respiration vs Fermentation
Carbohydrate Catabolism
• The breakdown of carbohydrate to release
energy involves
1. Glycolisis (cytoplasm)
2. Krebs cycle (mitochondrion)
3. Electron transport chain
Glycolysis
• Glycolysis (Embden Meyerhof pathway) is the
metabolic pathway used by most autotrophic
and heterotrophic organismsm to begin
breakdown of glucose
• Does not require oxygen, but occur in precense
or absence of oxygen
• Overall chemical reaction of Glycolysis
Glycolysis: Oxidation of Glucose
Glucose
2ATP
2 NAD+
2ADP
2NADH + 2H+
two Glyceraldehyde-3-PO4
4 ADP
4 ATP
two Pyruvate
23
P O CH2
HO CH2
O
OH
CH2 O P
O
PO4
OH
HO
OH
OH
OH
glucose
OH
fructose-1,6-diphosphate
CHO
2
H C OH
CH2O P
2 glyceraldehyde-3-phosphate
24
2 ADP + 2 Pi
2 ATP
CHO
CHO
2
H C OH
CH2O P
2
H C O
CH3
2 glyceraldehyde-3-phosphate
2 pyruvate
2 NAD+
2 NADH + 2 H+
25
Glycolysis: Oxidation of Glucose
Glycolysis generates
2 ATP molecules and 2 NADH + 2 H+
Two ATP used in adding phosphate groups to glucose and
fructose-6-phosphate (- 2 ATP)
Four ATP generated in direct transfer to ADP by two 3-C
molecules (+ 4 ATP)
Glucose + 2 ADP + 2 Pi + 2 NAD+
2pyruvate + 2 ATP + 2 NADH + 2 H+
26
Pathways for Pyruvate
Aerobic conditions
O
||
CH3–C –COO- + NAD+ + CoA
pyruvate
O
||
CH3–C –CoA + CO2 + NADH + H+
acetyl CoA
27
Pathways for Pyruvate
Anaerobic conditions (No O2 available)
Reduce to lactate to replenish NAD+ for glycolysis
O
||
CH3–C –COO- + NADH + H+
OH
|
CH3–CH –COO- + NAD+
pyruvate
lactate
enzyme: lactate dehydrogenase
28
Glycolysis
Alternative to Glycolysis
• Pentose phosphate pathway
a. Uses pentoses and NADPH
b. Operates with glycolisis
• Entner-Doudoroff pathway
a. Produces NADPH and ATP
b. Does not involve glycolisis
c.
Pseudomonas, Rhizobium, Agrobacterium
Intermediate step
• Pyruvic acid (from glycolysis) is oxidized and
decarboxylated
The Krebs Cycle/ The Citric acid cycle
(TCA cycle)
• Oxidation of acetyl Co-A produces NADH and
FADH2 (mitochondrion)
The Electron Transport Chain
• An electron transport chain (ETC) couples electron transfer between
an electron donor (such as NADH) and an electron acceptor (such as
O2) to the transfer of H+ ions (protons) across a membrane.
• A series of oxidation-reduction reactions, the electron transport
chain (ETC) performs 2 basic functions:
1. Accepting electrons from an electron donor and transferring them
to an electron acceptor
2. Conserving for ATP synthesis some of the energy released during
the electron transfer
• A series of carrier molecules that are, in turn oxidized and reduced
as electrons are passed down the chain
• Energy released can be used to produce ATP by chemiosmosis
The Electron Transport Chain
The Electron Transport Chain
Chemiosmosis
• Electrons from the hydrogen atoms removed
from the reactions of the Krebs cycle are
transferred through the electron transport
system
• Electron transport creates the H potential
across the membrane
• Combination of hydrogen/electron carriers
Chemiosmosis
Chemiosmosis
Questions?