9 Growth and Metabolism Running the Microbial Machine

Microbial Growth • Population growth – Growth curve • • • Logarithmic numbers Lag phase(휴지기, 유도기) Log phase(대수기) Stationary phase(정체기) Decline (death) phase(사멸기) Figure 9. 2: The growth curve for a bacterial population

Microbial Growth • Water and temperature – – – Psychrophiles(저온균) Facultative psychrophiles Mesophiles(중온균) Thermophiles(고온균) Hyperthermophiles(초고온균) Fig 9. 3: A) Moldy bread; B) Human large intestines harbor E. coli; C) Thermophilic algae © Jones and Bartlett Publishers. Photographed by Kimberly Potvin © Photodisc Courtesy of J Schmidt/Yellowstone National Park/NPS

Microbial Growth • Oxygen and acidity – – – Obligate aerobes(절대호기성균) Obligate anaerobes(절대혐기성균) Facultative anaerobes(통성혐기성균) Microaerophiles(미호기성균) Aerotolerant anaerobes

Microbial Growth • Oxygen and acidity – Acidophiles(호산성균) – Neutrophiles – Alkalophiles(호알카리성균) • Other factors – Salinity • Osmophiles • Halophiles(호염균) – Pressure • Barophiles(호압성균) – Radiation • Ultraviolet light • Gamma rays • X rays

Microbial Metabolism(미생물 대사) • 물질대사(metabolism): All the chemical changes occurring in a microbe during growth and development • Anabolism(합성반응, 합성대사) • Catabolism(분해반응, 분해대사)

Microbial Metabolism • Enzymes – – – Organic catalysts Coenzymes(조효소) Cofactors Substrates(기질) Active site(활성부위) Usually end in “-ase” Figure 9. 6: The mechanism of enzyme action

Microbial Metabolism • Energy – Metabolic processes designed to establish readily accessible source of energy – Photosynthesis(광합성) • Capture of energy in the form of glucose and other carbohydrates – Respiration(호흡) • Breakdown of glucose and other carbohydrates to capture their stored energy – Adenosine triphosphate (ATP) Figure 9. 7 a, b: Adenosine Triphosphate

Microbial Metabolism • Respiration and glycolysis(호흡과 해당과정) – Glycolysis(해당과정) • • Breakdown of glucose into 2 pyruvic acids Requires investment of 2 ATPs Generates 2 net ATPs Requires investment of 2 NAD+s Generates 2 net NADHs Occurs in cytoplasm Does not require O 2 First process in both aerobic and anaerobic breakdown of glucose

Microbial Metabolism: Glycolysis Figure 9. 8 1 -4: Glycolysis: Steps 1 -4

Microbial Metabolism: Glycolysis Figure 9. 8 Glycolysis: Steps 5 -9

Microbial Metabolism • Fermentation(발효) – Anaerobic process (no oxygen required) – Input is pyruvic acid – End products • Acid • Alcohol • Gas (e. g. , CO 2) – Means to recycle NADH to NAD+, to return to glycolysis – Saccharomyces uses fermentation to produce ethyl alcohol • All alcoholic beverages – Streptococcus and Lactococcus produce lactic acid • Converts condensed milk into yogurt – Other species use fermentation to age cheese

Microbial Metabolism: Fermentation Figure 9. 9: The relationship of fermentation to glycolysis

Microbial Metabolism • The Krebs cycle – Also known as citric acid cycle or tricarboxylic acid (TCA) cycle – Occurs in cytoplasm of prokaryotes, mitochondria of eukaryotes – Pyruvic acid must first be converted to acetyl-coenzyme. A (acetyl Co. A) • Release of one CO 2 per pyruvic acid • Conversion of one NAD+ to NADH per pyruvic acid • Since two pyruvic acids generated in glycolysis, net result is – 2 acetyl Co. A – 2 NADH – 2 CO 2 • Commits fate of glucose metabolism to aerobic breakdown and ATP generation

Microbial Metabolism • The Krebs cycle – Acetyl Co. A enters cycle – Joins with oxaloacetic acid to form citric acid – Multiple enzymatic steps that breakdown citric acid into oxaloacetic acid again in a “circle” or “cycle” – For each acetyl Co. A that enters cycle, net gain is • • 3 NADHs (converted from NAD+) 1 FADH 2 (converted from FAD) 1 GTP (from GDP plus inorganic phosphate, Pi) 2 CO 2 s – 1 glucose->2 pyruvic acids->2 acetyl Co. As • Cycle runs twice for each originally input glucose

Microbial Metabolism: The Krebs Cycle Figure 9. 10: The Krebs Cycle

7. 1

7. 2

Microbial Metabolism • The electron transport system and chemiosmosis(화학삼투) – Occurs at plasma membrane in prokaryotes – Occurs in mitochondria in eukaryotes – Electron transport chain • Cytochromes(철을 함유한 세포단백질로서 전자쌍을 전달하는 역할. ) • NADH relays its energy to cytochromes – NADH gets oxidized to NAD+ – High energy electrons from NADH enter electron transport chain – As electrons get passed to each member in the chain, they lose a little bit of energy, until they reach ground state – The energy provided by 1 NADH is used to pump 6 H+ ions across the membrane – Oxygen combines with the ground state electrons and H 2 to create water – This H+ pumping process is repeated 9 more times, once for each NADH from glycolysis, conversion of pyruvic acid to acetyl Co. A, and the Krebs cycle – Total of 60 H+ moved across membrane for all NADHs

Microbial Metabolism • The electron transport system and chemiosmosis – Chemiosmosis(화학삼투) • ATP synthetase • Energy drop of 2 H+s moving down their concentration gradient is used to synthesize 1 ATP from ADP + Pi • 68 H+s moving through ATP synthetase equates to 34 ATPs just from chemiosmosis – Sum of ATP output from complete aerobic breakdown of glucose • • Glycolysis: 2 ATP Krebs cycle: 2 GTP <-> 2 ATP Chemiosmosis: 34 ATP Total of 38 ATP, or more accurately, 36 ATP + 2 GTP

Microbial Metabolism • Anaerobic metabolism(혐기적대사) – – The sum of glycolysis plus fermentation Oxygen is not terminal electron acceptor Escherichia coli reduce nitrate (NO 3 -) to nitrite (NO 2 -) Some cells utilize SO 4 - as terminal electron acceptor, converting it to H 2 S – Others use CO 2, converting it to CH 4 – Useful way to obtain energy before O 2 filled atmosphere

Microbial Metabolism • Photosynthesis – – Biosynthetic Requires energy from sunlight Light reactions are energy-trapping(에너지 포집반응) Dark reaction are carbon-trapping(탄소포집반응)

Microbial Metabolism • Photosynthesis – Light reactions • Chlorophyll absorbs solar energy • Solar energy is used to energize electrons in chlorophyll • Electrons from chlorophyll enter transport chain, akin to aerobic metabolism • ATP is synthesized through chemiosmosis, much like aerobic metabolism • NADP+ is also converted to NADPH from this light energy – Dark reactions • Energy from ATP and NADPH in light reactions is utilized • Series of condensations to create glucose from CO 2 – Electrons in chlorophyll must still be replaced • Usually pulled from water • Byproduct is O 2, released to atmosphere

Microbial Metabolism: Photosynthesis Figure 9. 12 b: Photosynthesis in microbes : 탄소포집반응 : 1) 이산화탄소는 ribulose bisphosphate(Ru. BP)와 결합되어 불안정한 6 -탄소 분자가 된다. 2) 2분자의 phospho glyceraldehyde(PGAL)가 된다. 3) 2개의 3 -탄소 PGAL분자들은 결국 포도당을 만들고 4) 나머지는 ATP와 함께 ribulose bisphosphate를 형성하기 위해 이용되고 반응은 계 속된다.