MICROBIOLOGIA GENERALE Microbial metabolisms 1

Overview of the cellular metabolism

catabolism: aims and products Microbial metabolism catabolism: aims and products

High energy compounds and energy storage

Structure of the oxidation–reduction coenzyme nicotinamide adenine dinucleotide (NAD+)

energy conservation: options Microbial metabolism energy conservation: options

Carbon source classes of Microorganisms Autotrophs Eterotrophs Energy classes of Microorganisms Phototrophs Chemotrophs Chemoorganotrophs Chemolithotrophs

Metabolic options for obtaining energy

AEROBES ANAEROBES Aerotolerant Group Relationship to O2 Type of metabolism Example AEROBES Obligate Required Aerobic respiration Micrococcus luteus Facultative Not required, growth better with O2 Aerobic respiration or Fermentation Esherichia coli Microaerophilic Required at low levels Spirillum volutans ANAEROBES Aerotolerant Not required, growth no better with O2 Fermentation Streptococcus pyogenes Harmful or lethal Fermentation or Anaerobic respiration Clostridium tetani

H20, H2S, S, organic molecules Metabolism e- donor e- acceptor Microorganisms Fermentation Organic molecules Organic molecule Obligately anaerobic and facultative chemoorganotrophic Aerobic Respiration Organic molecules Inorganic O2 Obligately aerobic and facultative Chemolithotrophs Anaerobic Respiration Organic or inorganic molecules NO3 SO4 CO2 Nitrate reducers Sulfate reducers Methanogenic Photosynthesis H20, H2S, S, organic molecules NADP NADPH Cyanobacteria, Green and Purple bacteria

Microbial metabolism fermentation

H20, H2S, S, organic molecules Metabolism e- donor e- acceptor Microorganisms Fermentation Organic molecules Organic molecule Obligately anaerobic and facultative chemoorganotrophic Aerobic Respiration Organic molecules Inorganic O2 Obligately aerobic and facultative Chemolithotrophs Anaerobic Respiration Organic or inorganic molecules NO3 SO4 CO2 Nitrate reducers Sulfate reducers Methanogenic Photosynthesis H20, H2S, S, organic molecules NADP NADPH Cyanobacteria, Green and Purple bacteria

Overall process of FERMENTATION In a typical fermentation, most of the carbon is excreted as a partially reduced end product of energy metabolism and only a small amount is used in biosynthesis

Glycolysis The glucose catabolism Shunt hexose monophosphate Pentose enteric bacteria and homofermentative lactic acid bacteria The glucose catabolism Shunt hexose monophosphate heterofermentative lactic acid bacteria Pentose phosphate Pyruvate Enter-Doudoroff Pseudomonas Rhizobium

The Entner-Doudoroff pathway (Pseudomonas, Rhizobium)

Embden-Meyerhof-Parnas (EMP) pathway (glycolysis)

The catalytic cycle of the enzyme fructose bisphosphate aldolase

Butyric acid Propionic acid Lactic acid Alcohol Pyruvate Mixed Acids Clostridium Propionic acid Propionibacterium Lactic acid Homofermentative Heterofermentative bacteria Alcohol Saccharomyces Pyruvate Mixed Acids Escherichia 2,3-Butanediol Enterobacter

Alcohol Saccharomyces

Lactic acid Homofermentative bacteria

Homolactic fermentation (Streptococcus, Lactococcus)

Lactic acid Heterofermentative bacteria

Heterolactic fermentation (Leuconostoc, Lactobacillus)

Lactic fermentation through the fructose-6-phosphate pathway (Bifidobacterium)

Mixed acids fermentation (Escherichia, Salmonella, Shigella)

2,3-Butanediol fermentation (Enterobacter, Klebsiella, Serratia)

2,3-Butanediol fermentation Voges-Proskauer test

Propionic acid fermentation The formation of propionic acid by Propionibacterium

Butyric acid fermentation (Clostridium)

Coupled oxidation-reduction between Ala and Gly in Clostridium sporogenes

aerobic respiration in chemoorganotrophs Microbial metabolism aerobic respiration in chemoorganotrophs

H20, H2S, S, organic molecules Metabolism e- donor e- acceptor Microorganisms Fermentation Organic molecules Organic molecule Obligately anaerobic and facultative chemoorganotrophic Aerobic Respiration Organic molecules Inorganic O2 Obligately aerobic and facultative Chemolithotrophs Anaerobic Respiration Organic or inorganic molecules NO3 SO4 CO2 Nitrate reducers Sulfate reducers Methanogenic Photosynthesis H20, H2S, S, organic molecules NADP NADPH Cyanobacteria, Green and Purple bacteria

Energetics and carbon flow in chemoorganotrophic respiratory metabolism

Energy conservation in fermentation and respiration

Electron transport chains and their relation to E0’. An electron transport system ,leads to the transfer of electrons from substrate to O2

Flavin mononucleotide (FMN) (riboflavin phosphate, a hydrogen atom carrier)

Arrangement of the iron Fe2S2 center Arrangement of the iron sulfur centers of nonheme iron-sulfur proteins that carry electrons only Fe4S4 center

Structure of oxidized and reduced forms of coenzyme Q, a quinone

Cytochrome and its structure

Generation of the proton motive force during aerobic respiration and the orientation of key electron carriers in the membrane

Orientation of key electroncarriers in the membrane of E. coli

Modular organization of the electroncarriers in E. coli

Structure and function of ATP synthase (ATPase)

Structure and function of ATP synthase (ATPase) of E. coli

Aerobic respiration of organic substrates in prokaryotes Carbohydrates Pyruvate Amino acids Acetyl-CoA Fatty acids Citric acid cycle

Aerobic respiration of organic substrates in prokaryotes

The citric acid cycle (CAC)

The overall balance of the aerobic respiration Alcohol fermentation 2 ATP per glucose

The overall balance of the aerobic respiration