1
Microbiology Microbial Metabolism II Catabolism & Anabolism Ching-Tsan Huang (黃慶璨) Office: Room 111, Agronomy Hall Tel: (02) 33664454 E-mail:
[email protected]
2
Anabolism Use of Energy in Biosynthesis Turnover Carefully regulated
Catabolism Energy Release and Conservation Provide materials for biosynthesis Amphibolic pathways
3
Amphibolic Pathways
4
Source of Energy for Microorganisms Phototrophy
Chemoorganotrophy Chemolithotrophy
Chemical Energy Work
Chemoorganotrophic Catabolisn Respiration
Aerobic Respiration
Anaerobic Respiration
Fermentation
5
6
Chemoorganotrophic Metabolism Aerobic respiration using oxygen as exogenous electron acceptor yields large amount of energy, primarily by electron transport activity
Anaerobic respiration using molecules other than oxygen as exogenous electron acceptors yields large amount of energy, primarily by electron transport activity
Fermentation using endogenous electron acceptor often occurs under anaerobic conditions limited energy made available
7
Overview of Aerobic Catabolism
8
Carbohydrate Catabolism: GlucoseÆPyruvate Glycolysis Most common Also called EmbdenMeyerhof pathway Occurs in cytoplasmic matrix of both procaryotes and eucaryotes Generation of NADH ATP synthesis via substrate-level phosphorylation Glucose + 2 ADP + 2 Pi + 2 NAD+
2 Pyruvate + 2 ATP + 2 NADH + 2 H+
9
Carbohydrate Catabolism: GlucoseÆPyruvate Pentose Phosphate Pathway provide NADPH as source of electrons 4-carbon sugar for aromatic amino acid synthesis and 5-carbon sugar for nucleic acid synthesis and CO2 acceptor Aerobic or anaerobic 3 Glucose-6-P + 6 NADP+ + 3 H2O 2 Fructose-6-P + Glyceraldehyde-3-P + 3 CO2 + 6 NADPH + 6 H+
10
Carbohydrate Catabolism: PyruvateÆCO2 Aerobic Use O2 as eacceptor TCA (tricaboxylic acid) cycle or Citric acid cycle or Kreb’s cycle
Function Provide carbon skeletons for use in biosynthesis
11
Electron Transport Electron transport chain in the inner membrane of the mitochondrion in the bacterial plasma membrane
Electron donors: NADH (3 ATPs) FADH2 (2 ATPs)
Electron acceptor: Oxidative phosphorylation: process by which energy from electron transport is used to make ATP Wolinella succinogenes is a nonfermenting bacterium with fumurate as its sole carbon source. It undergoes anaerobic fumerate respiration.
12
Carbohydrate Catabolism: Glucose Æ CO2
13
Fermentations
14
Carbohydrate Catabolism: PyruvateÆCO2 Anaerobic Fermentation No exogeneous eacceptor Use organic molecules as eacceptor ATP formed by substrate-level phosphorylation
15
Lipid Catabolism Lipid
Fatty acid + Glycerol
Fatty acid β-oxidation
16
Protein and Amino Acid Catabolism Protease Hydrolysis of protein to amino acids
Deamination Often occurs by transamination
17
Principles Governing Biosynthesis Macromolecules are synthesized from limited number of simple structural units (monomers) Many enzymes used for both catabolism and anabolism Catabolic and anabolic pathways are not identical, despite sharing many enzymes Breakdown of ATP coupled to certain reactions in biosynthetic pathways Catabolic and anabolic pathways use different cofactors Large assemblies (e.g., ribosomes) form spontaneously from macromolecules by self-assembly
18
Energy Trapping: Photosynthesis
Anoxygenic Oxygenic
Light reaction light energy is trapped and converted to chemical energy
Dark reaction reduce or fix CO2 and synthesize cell constituents
19
Light Reaction Eucaryotes & Cyanobacteria
Green & Purple Bacteria
PMF Reversed e- flow
20
Photosynthetic Fixation of CO2 Autotrophs obtain energy by trapping light during photosynthesis or by oxidizing or reduced inorganic e- donors Calvin, Calvin-Benson, reductive pentose phosphoraltion cycle in eucaryotes, occurs in stroma of chloroplast in cyanobacteria, some nitrifying bacteria occur in carboxysomes
Carboxylation
Reduction
6 RuBP + 6 CO2 12 PGA 6 RuBP + Fructose 6-P
Regeneration
21
Synthesis of Pyruvate to Glucose Gluconeogenesis: Heterotrophs synthesize sugars by reducing organic molecules
Glucoeogenesis
Glycolysis
22
Synthesis of Sugars and Polysaccharides Gluconeogenesis synthesize glucose and fructose from noncarbohydrate precursors
Sugar nucleoside diphosphates synthesis of other sugars , polysaccharides, and bacterial cell walls ATP + glucose 1-P → ADP-glucose + PPi (glucose)n + ADP-glucose → (glucose)n+1 + ADP
23
Synthesis of Amino Acids Precursor metabolites used as starting substrates carbon skeleton is remodeled amino group and sometimes sulfur are added
Nitrogen addition to carbon skeleton is important potential sources of nitrogen: ammonia, nitrate, or nitrogen
24
Synthesis of Amino Acids
Phosphoenolpyruvate
Oxaloacetate
α-ketoglutarate
25
Lipid Synthesis Fatty acid synthesis
ACP: acryl carrier protein
Triacrylglycerols & phospholipids