Running the Microbial Machine 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) © Jones and Bartlett Publishers. Photographed by Kimberly Potvin Fig 9.3: A) Moldy bread; B) Human large intestines harbor E. coli; C) Thermophilic algae © 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 Other factors 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)

Figure 9.6: The mechanism of enzyme action 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 9.7a,b: Adenosine Triphosphate

Microbial Metabolism Respiration and glycolysis(호흡과 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 O2 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., CO2) 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-coenzymeA (acetyl CoA) Release of one CO2 per pyruvic acid Conversion of one NAD+ to NADH per pyruvic acid Since two pyruvic acids generated in glycolysis, net result is 2 acetyl CoA 2 NADH 2 CO2 Commits fate of glucose metabolism to aerobic breakdown and ATP generation

Microbial Metabolism The Krebs cycle Acetyl CoA 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 CoA that enters cycle, net gain is 3 NADHs (converted from NAD+) 1 FADH2 (converted from FAD) 1 GTP (from GDP plus inorganic phosphate, Pi) 2 CO2s 1 glucose->2 pyruvic acids->2 acetyl CoAs Cycle runs twice for each originally input glucose

Microbial Metabolism: The Krebs Cycle Figure 9.10: The Krebs Cycle

7.1

7.2

이론적으로 총 38 ATP가 생성되나 실제는 이론치보다 적은 양이 생성된다. 호기성 호흡으로부터 생성되는 에너지 호기성호흡을 하는동안 포도당으로부터 생성되는 이론적인 에너지의 양은 형성되는 ATP의 수를 계산. 2 ATP가 EM경로에서 생성된다. 2 ATP가 TCA회로에서 생성된다. 30 ATP : 10개의 pyridine nucleotide (NADH/NADPH)가 재산화하면서 만들어진다. 4 ATP : 2개의 flavin nucleotide가 재산화하면서 생성된다. 이론적으로 총 38 ATP가 생성되나 실제는 이론치보다 적은 양이 생성된다. Pentose-phosphate 경로 : 1개의 ATP가 만들어지며 핵산 합성을 위한 ribose-5-phosphate, 그리고 방향족 아미노산의 합성을 위한 erythrose-4-phosphate와 같은 중간 대사산물을 생합성한다.

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 H2 to create water This H+ pumping process is repeated 9 more times, once for each NADH from glycolysis, conversion of pyruvic acid to acetyl CoA, and the Krebs cycle Total of 60 H+ moved across membrane for all NADHs

Figure 9.11 : 세균에서의 전자전달과 화학삼투 : (A) NADH는 세포막에서 cytochrome 들로 전자쌍을 전달한다. (B) NAD 혹은 FAD 조효소는 재사용을 위해 재생된다. (C) 세포막을 가로지르는 수소이온의 수송 (D) 수소이온들은 ATP synthase와 연관된 단백질통로를 통해 세포질로 다시들어간다. (E) 그통로를 통해 한쌍의 수소이온이 이동할 때마다 3개의 ADP분자들은 인산기와 3개의 ATP분자가 생성된다. (F) 전자들은 산소원자와 결합하여 물 분자들을 생성한다.

Microbial Metabolism The electron transport system and chemiosmosis 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 (NO3-) to nitrite (NO2-) Some cells utilize SO4- as terminal electron acceptor, converting it to H2S Others use CO2, converting it to CH4 Useful way to obtain energy before O2 filled atmosphere

산소가 제한될 경우 : 균류를 비롯한 많은 생명체들은 산소가 없어도 다음 반응들 중의 한가지 방법에 의해서 에너지를 얻을 수 있다.

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 Dark 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 CO2 Electrons in chlorophyll must still be replaced Usually pulled from water Byproduct is O2, released to atmosphere

Microbial Metabolism: Photosynthesis Figure 9.12a: Photosynthesis in microbes : Cyanobacterium의 막을 따라 일어나는 에너지 포집반응. 1)엽록소에 있는 전자들이 빛에너지에 의해 활성화되고, 2)ATP는 전자들이 전자전달계를 통과할 때 합성된다. 3) 전자들이 두번째로 활성화되고 4) 에너지는 고에너지 NADPH를 생성하는데 이용된다.

Microbial Metabolism: Photosynthesis Figure 9.12b: Photosynthesis in microbes : 탄소포집반응 : 1) 이산화탄소는 ribulose bisphosphate(RuBP)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 계속된다.