microbial metablism
DESCRIPTION
Microbial metablism. Catabolism, anabolism Fermentation Respiration Nitrogen fixtation The synthesis of peptiglydogen. An overview of metabolism. Metabolism may be divided into two major parts: catabolism and anabolism . - PowerPoint PPT PresentationTRANSCRIPT
Microbial metablism
Catabolism, anabolism
Fermentation
Respiration
Nitrogen fixtation
The synthesis of peptiglydogen
An overview of metabolism
• Metabolism may be divided into two major parts: catabolism and anabolism.
• Catabolism: larger and more complex molecules are broken down into smaller, simpler molecules with the release of energy.
• Anabolism: the synthesis of complex molecules from simpler ones with the input of energy.
The three
stages of
catabolism
• Carbohydrates and other nutrients serve two functions in the metabolism of heterotrophic microorganisms:
1. They are oxidized to release energy2. They supply carbon or building blocks for the
synthesis of new cell constituents.• Amphibolic pathways: function both
catabolically and anabolically
• Much of the ATP derived from the TCA cycle comes from the oxidation of NADH and FADH2 by the electron transport chain.
SUGAR CATABOLISM
• Glycolysis (Embden, Meyerhof Parnas Glycolysis (Embden, Meyerhof Parnas Pathway)Pathway)
– most bacteriamost bacteria– also animals and plantsalso animals and plants
Other pathways for catabolizing sugars
• Pentose phosphate pathway (hexose Pentose phosphate pathway (hexose monophosphate shunt)monophosphate shunt)– generates NADPHgenerates NADPH– common in plants and animalscommon in plants and animals
• Entner Doudoroff Pathway Entner Doudoroff Pathway – a few bacterial speciesa few bacterial species
GlycolysisGlycolysis
NADNAD NADHNADH
GlucoseGlucose PyruvatePyruvateC6C6 C3C3
ADP ADP ATPATP
FermentationFermentation
2. 2. PyruvatePyruvate
((C3)C3)
1. 1. NADHNADH NADNAD
Short chain alcoholsShort chain alcohols, , fatty acidsfatty acids((C2-C4)C2-C4)
The energy substrate is oxidized and degraded without the participation of an exogenous or extrenally derived electron acceptor. Usually an intermediate such as pyruvate acts the electron acceptor. Anaerobic conditions
Two unifying themes should be kept in mind when microbial fermentation are examined:
Three type fermentation of Saccharomyces cerevisiae
I: pyruvateacetaldehydeethanolII: pH7: glycerolIII: NaHSO3
Lactic acid fermentation
• The reduction of pyruvate to lactate
• Homofermentative(同型发酵的) group: produces only lactic acid as sole product
• Heterofermentative(异型发酵的) group: produces ethanol, CO2 and lactic acid
Respiration
Energy-yielding metablism can make use of exogenous or externally derived electron acceptors.Two different type:
aerobic respiration: the final electron acceptor is oxygen
anaerobic respiration: most often is inorganic such as NO3
-, SO42-, CO2 , Fe3+,
SeO42 -,)
Anaerobic Respiration = Anaerobic Respiration = Glycolysis + FermentationGlycolysis + Fermentation
NADNAD NADHNADH
NADHNADH NADNAD
ATPATP
Krebs Cycle (C4-C6 intermediate compoundsKrebs Cycle (C4-C6 intermediate compounds)
PyruvatePyruvate 33COCO22
((C3)C3)
NADNAD NADHNADH
NADHNADH NADNAD
Oxidative phosphorylationOxidative phosphorylation
OO22 HH22OO
ADPADP ATPATP
((C1)C1)
Aerobic Respiration =Aerobic Respiration =Glycolysis + Glycolysis +
Krebs Cycle/oxidative phosphorylationKrebs Cycle/oxidative phosphorylation
• Pyruvate to COPyruvate to CO22
– NADNAD toto NADHNADH
– glycolysis glycolysis
– Krebs cycleKrebs cycle
• Oxidative phosphorylationOxidative phosphorylation
– NADHNADH to to NAD NAD
– ADPADP to to ATP ATP
Oxidative phosphorylationOxidative phosphorylation
• converts Oconverts O22 to H to H220 0 (oxidative)(oxidative)
• converts ADP to ATP converts ADP to ATP (phosphorylation)(phosphorylation)
• electron transport chainelectron transport chain
• ubiquinones/cytochrome intermediates ubiquinones/cytochrome intermediates
Sugar as sole carbon sourceSugar as sole carbon source
PyruvatePyruvate (C3)(C3)
AcetateAcetate(C2)(C2)
--COCO22
C6C6
Krebs CycleKrebs Cycle
C4C4
PyruvatePyruvate (C3)(C3)
+ + COCO22
FATTY ACIDS AS SOLE CARBON FATTY ACIDS AS SOLE CARBON
SOURCESOURCE
Fatty acidsFatty acids
AcetateAcetate(C2)(C2)
C6C6
Krebs CycleKrebs Cycle
C4C4 C4C4 C2C2++
The glyoxylate cycleThe glyoxylate cycle
.
-
+
C3 C2
C4
C6
C2
C2
C4
C4
C4
C5
C6
Krebs CycleKrebs Cycle
– biosyntheticbiosynthetic
– energy producing energy producing
• Removal of intermediatesRemoval of intermediates
– must be replenished. must be replenished.
• Unique enzymatic replenishment pathwayUnique enzymatic replenishment pathway
– sugars sugars
– fatty acidsfatty acids
Nitrogen fixation
The reduction of atmospheric gaseous nitrogen
to ammonia is callled nitrogen fixation.
Nitrogen fixation occurs in:1. Free-living bacteria.(Azotobacter)2. Bacteria living in symbiotic association with plants such as legumes(Rhizobium)3. cyanobacteria
Nitrogenase
Consistiong of two major protein components: a MoFe protein joined with one or two Fe proteins.1. The MoFe protein contains 2 atoms of molybdenum and 28 to 32 atoms of iron;2. The Fe protein has 4 iron atoms
Mechnisms of anti-oxygen
Nitrogenase is quite sensitive to O2 and must be protected from O2
inactivation within the cell.1.Respiration protection2.Hetercyst formation3.Membrane
Nitrogen reductionN2+8H++8e-+16ATP2NH3+H2+16ADP+16Pi
Root Nodule Bacteria and Symbiosis with legumes
Soybean root nodules Unnodulated soybean
Nodulated soybean
Steps in the formation ofroot nodule in a legumeinfected by Rhizobium
Peptidoglycan synthesis
Staphylococcus aureus
Two carriers participate: uridine diphosphate (UDP) and bactoprenol
BactoprenolBactoprenol is a 55-carbon alcohol that attaches to NAM by a pyrophosphate group and moves peptidoglycan components through the hydrophobic membrane
Eight stages of Peptidoglycan synthesis
1. The formation of UDP-NAM and UDP-NAG2. Amino acids are sequentially added to UDP-
NAM to form the pentapeptide chain.3. The NAM-pentapeptide is transferred from
UDP to a bactoprenol phosphate at the membrane surfacre.
4. UDP-NAG adds NAG to the NAM-pentapeptide to form the peptidoglycan repeat unit.
5. Repeat unit is transported across the membrane to its outer surface by the bactoprenol pyrophosphate carrier.
6. The peptidoglycan unit is attached to the growing end of a peptidoglycan chain to lengthen it by one repeat unit.
7. The bactoprenol carrier returns to the inside of the membrane. A phosphate is released.
8. Peptide cross-links between the peptidoglycan chains are formed by transpeptidation.
Eight stages of Peptidoglycan synthesis
Peptidoglycan synthesis
CytoplasmCytoplasm Cell wallCell wall
undecaprenolundecaprenol
sugarsugar
aminoaminoacidacid
Cell MembraneCell Membrane
Peptidoglycan SynthesisTransport of peptidoglycan precursors across the
cytoplasmic membrane to the growing point of the cell wall
The transpeptidation reaction that lead to the final cross-linking of two peptidoglycan chains
Penicillin inhibits this reaction
Questions
• What are catabolism and anabolism?
• What are Fermentation and Respiration?
• Lactic acid fermentation• aerobic respiration, anaerobic respiration• Nitrogen fixation• Why is Root nodule bacteria and symbiosis so
important for legumes?• Eight stages of Peptidoglycan synthesis