Chapter 5Microbial Nutrition and Culture
Chapter 5Microbial Nutrition and Culture
Siti Sarah Jumali (ext 2123)
Room 3/14
sarah_jumali84@hotmail.com
Groups of bugs based on energycapture and carbon source
•AUTOTROPHY: Use carbondioxide to synthesize organicmolecules
•Two types:
1.Photoautotrophs: obtain energyfrom light
2.Chemoautotrophs: obtain energyfrom oxidizing simple inorganicsubstance
Groups of bugs based on energycapture and carbon source cont’d
•HETEROTROPHY: Get carbon dioxide fromready made organic molecules
•Two types:
1.Photoheterotrophs: obtain chemical energyfrom light
2.Chemoheterotrophs: obtain energy frombreaking down ready-made organiccompounds
The main types of energy capturing Metabolism
Allmicroorganisms
Inorganic CO2 = carbon source AUTOTROPH
(Self feeders)
Making own food by reducing CO2
Photoautotrophs
Chemoautotrophs
Organic compound = carbon sourceHETEROTROPH
Using ready-made organic molecules for food
Photoheterotrophs
Chemoheterotrophs
Examples of Energy Source
Type
Energy Source
Carbon Source
Examples
Photolithotrophs
Light
CO2
Algae,Purple sulphurbacteri,green sulphurbacteria
Photoorganotrophs
Light
Organic Compounds
Purple non sulphurbacteria
Chemolithotrophs
Oxidation ofinorganic compounds
Nitrifyingbacteria,ironbacteria,H2 bacteria
Chemoorganotrophs
Oxidation of organiccompounds
Organic Compounds
Most bacteria,fungi,protozoa
Photosynthesis and Respiration
Metabolism
•The sum of all chemical processes carried out by livingorganisms
•Anabolism: rxn that requires energy in order tosynthesize complex molecules from the simpler ones
- (use energy and building blocks to build largemolecules)
•Catabolism: rxn that releases energy by breakingcomplex molecules into simpler ones which can bereused as building blocks
- (provides energy and building blocks for anabolism)
Metabolism: The sum of catabolismand anabolism
Largermolecules
SmallerMolecules
Catabolism
Anabolism
Energy
Metabolic Pathway
•Glycolisis, fermentation, aerobic respiration andphotosynthesis each consists of a series of chemicalreaction
•The product of one reaction serves as the substrate for thenext: ABCD
•Such chain of reactions is called a metabolic pathway:
- Anabolic pathways make the complex molecules thatform structure of cells, enzymes and molecules thatcontrol cells
- Catabolic pathways capture energy in a form a cell canuse
Oxidation-Reduction Reactions
•All catabolic reactions involve electrontransfer which is directly related to oxidationand reduction (redox potential)
•Redox reaction: An oxidation reaction pairedwith a reduction reaction
- Oxidation: the loss of removal of electrons
-Reduction: the gain of electrons
Oxidation-Reduction Reactions
Representative Biological Oxidations
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 LEOsays GER
•Electron Loss Means Oxidation: ELMO
In biological systems, the electrons are oftenassociated with hydrogen atoms. Biologicaloxidations are often dehydrogenation.
13
Metabolic Pathways of Energy Production
Metabolic Pathways of EnergyProduction
(b)
•Carrier molecules such as Cytochrome (cyt) andsome coenzymes carry energy in the form ofelectrons in many biochemical reactions
•Coenzymes such as FAD carry whole hydrogenatoms (electrons together with protons); NADcarries one hydrogen atom and one “naked”electron
•When co-enzymes are reduced, they increase inenergy, when they are oxidized, they decrease inenergy.
Energy Transfer by Carrier Molecules
Energy Generation of ATP
•ATP is generated by the phosphorylation ofADP
ADP + Pi + Energy ATP
•In cells, energy is provided by the hydrolysis ofATP
ATP ADP + Pi + Energy
Energy
Energy
Generation of ATP
1.Substrate level Phosphorylation: Energy from thetransfer of a high energy PO4 to ADP generates ATP
C-C-C-P + ADP C-C-C + ATP
2.Oxidative Phosphorylation: Energy relseased fromtransfer of electrons (oxidation) of one compound toanother (reduction) is used to generate Atp in theelectron transport chain
3.Photophosporylation: Light causes chlorophyll to giveup electrons. Energy released from transfer ofelectrons (oxidation) of chlorophyll trough a system ofcarrier molecules is used to generate ATP
Overview of Respiration vs Fermentation
Carbohydrate Catabolism
•The breakdown of carbohydrate to releaseenergy involves
1.Glycolisis (cytoplasm)
2.Krebs cycle (mitochondrion)
3.Electron transport chain
Glycolysis
•Glycolysis (Embden Meyerhof pathway) is themetabolic pathway used by most autotrophicand heterotrophic organismsm to beginbreakdown of glucose
•Does not require oxygen, but occur in precenseor absence of oxygen
•Overall chemical reaction of Glycolysis
23
Glycolysis: Oxidation of Glucose
2ATP
2 NAD+
2ADP2NADH + 2H+
4 ADP
4 ATP
Glucose
two Glyceraldehyde-3-PO4
two Pyruvate
24
2 NAD+ 2 NADH + 2 H+
25
26
Glycolysis: Oxidation of Glucose
Glycolysis generates
2 ATP molecules and 2 NADH + 2 H+
Two ATP used in adding phosphate groups to glucose andfructose-6-phosphate (- 2 ATP)
Four ATP generated in direct transfer to ADP by two 3-Cmolecules (+ 4 ATP)
Glucose + 2 ADP + 2 Pi + 2 NAD+
2pyruvate + 2 ATP + 2 NADH + 2 H+
27
Pathways for Pyruvate
Aerobic conditions
O
||
CH3–C –COO- + NAD+ + CoA
pyruvate
O
||
CH3–C –CoA + CO2 + NADH + H+
acetyl CoA
28
Pathways for Pyruvate
Anaerobic conditions (No O2 available)
Reduce to lactate to replenish NAD+ for glycolysis
O OH
|| |
CH3–C –COO- + NADH + H+ CH3–CH –COO- + NAD+
pyruvate lactate
enzyme: lactate dehydrogenase
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 anddecarboxylated
The Krebs Cycle/ The Citric acid cycle(TCA cycle)
•Oxidation of acetyl Co-A produces NADH andFADH2 (mitochondrion)
The Electron Transport Chain
•An electron transport chain (ETC) couples electron transfer betweenan electron donor (such as NADH) and an electron acceptor (such asO2) to the transfer of H+ ions (protons) across a membrane.
•A series of oxidation-reduction reactions, the electron transportchain (ETC) performs 2 basic functions:
1.Accepting electrons from an electron donor and transferring themto an electron acceptor
2.Conserving for ATP synthesis some of the energy released duringthe electron transfer
•A series of carrier molecules that are, in turn oxidized and reducedas 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 removedfrom the reactions of the Krebs cycle aretransferred through the electron transportsystem
•Electron transport creates the H potentialacross the membrane
•Combination of hydrogen/electron carriers
Chemiosmosis
Chemiosmosis
Questions?