Yeasts and bacteria on berry surface can imitate fermentation and produce alcohol
Drunkenness by microbes - Candida albicans 白色念珠菌
第五章 : 微生物代谢和发酵
Content 1. Energy release and conservation Heterotroph Autotroph 1. The use of energy in microbial biosynthesis Special microbial pathway
Metabolism 新陈代谢 - all chemical reactions within a living organism 1. Catabolism 分解代谢 breakdown Complex organic simpler compounds 2. Anabolism 合成代谢 building releases ENERGY Simpler compounds Complex organic requires ENERGY
The Primary Energy Source 最初能源 Primary energy source Light energy 日光 Organic compound 有机化合物 Inorganic compound 无机化合物 ATP
Classes of Enzymes 酶的类型 Class Oxidoreductase 氧化还原酶 Transferase 转移酶 Hydrolase 水解酶 Lyase 裂解酶 Isomerase 同分异构酶 Ligase 连接酶 Chemical Reaction Catalyzed Oxidation-reduction in which oxygen and hydrogen are gained or lost Transfer of functional groups, such as an amino group, acetyl group, or phosphate group Hydrolysis (addition of water) Removal of groups of atoms without hydrolysis Rearrangement of atoms within a molecule Joining of two molecules (using energy usually derived from the breakdown of ATP) Sample Enzymes Cytochrome oxidase, lactate dehydrogenase Acetate kinase, alanine deaminase 丙氨酸脱氨基酶 Lipase, sucrase Oxalate decarboxylase, isocitrate 异柠檬酸 lyase Glucose-phosphate isomerase, alanine racemase 丙氨酸消旋酶 Acetyl-CoA synthetase, DNA ligase
Metabolism of Chemoheterotroph s 化能异养微生物的 生物氧化和产能
Biological Oxidation 生物氧化 Three stages 1. Loss of hydrogen or electron 脱氢 2. Hydrogen or electron transfer 递氢 Acceptance of hydrogen or electron 受氢 Products ATP Reduction power [H] 还原力 Intermediate metabolites 中间代谢物
Carbohydrate Catabolism 碳水化合物分解代谢 Primary energy source 碳水化合物是主要能源 Glucose 葡萄糖 - most common energy source Respiration 呼吸 & Fermentation 发酵作用 好气微生物, 适宜条件下
SUGAR CATABOLISM 糖分解代谢
1. Glycolysis 糖酵解 (EMP Pathway) Most common pathway Most prokaryotes and eukaryotes 10 steps, 11 enzymes in cytoplasm Fate of glycolysis products aerobic 有氧 : TCA completely oxidize pyravate 丙酮酸 anerobic 无氧 : fermentation ethanol 乙醇 or lactic acid 乳酸
1. Glycolysis: Two stages 糖酵解的二个阶段
Energy Production in Glycolysis 糖酵解的产能
Overview of Glycolysis
Science: predicts the hot topic in 2010 Cancer cells: usually change from aerobic glycolysis (anaerobic) New way to kill cancer cells?
Also: hexose monophosphate shunt Glucose oxidized completely Sugar of C3-C7 produced Generates a great amount of NADPH 产生大量还原型辅酶 II Common in plants and animals
The pentose phosphate pathway 6- 磷酸葡糖酸 氧化型谷胱甘肽 还原型谷胱甘肽
木酮糖 Intermediates of HMP 己糖磷酸支路中间产物
The Pentose Shunt connected to other metabolism pathways 与其他代谢途径的关系 赤藓糖 C4
Only exits in a few EMP-lacked bacterial 仅存在于缺少 EMP 途径的少数细菌中 Glucose is oxidized rapidly to pyruvate via a shorter pathway 葡萄糖经较短途径氧化成丙酮酸 Specificity 特点 : 1. KDPG aldolase 醛缩酶 2. Two molecules of pyruvate come from different source 两分子的丙酮酸来自不同途径 3. Low efficiency of energy production 产能效率低
ED Pathway One molecule of pyruvate is converted from glyceraldehyde
Anaerobic Respiration 无氧呼吸 Final e- acceptor: not oxygen Nitrate 硝酸盐 respiration=dinitrification 反硝化 Nitrate 硝酸盐 (NO 3 - ) ----> Nitrite (NO 2- ) 亚硝酸 Sulfate respiration 硫酸盐呼吸 : Sulfate (SO 4 2- ) ----> Hydrogen Sulfide (H 2 S) Carbonate respiration 碳酸盐呼吸 Carbonate (CO 3 2- ) -----> Methane 甲烷 (CH 4 )
Respiration 呼吸作用 e- acceptor
Fermentation 发酵作用 = Glycolysis + an additional step O 2 is not the final e- acceptor
(1) Lactic Acid Fermentation 乳酸发酵 pyruvate + NADH lactic acid + NAD + Only 2 ATP 2 Genera 属 : Streptococcus 链球菌 Lactobacillus 乳杆菌属 Lactobacillus spp.
Significance of Lactic acid fermentation Found in bacteria, some protozoa 原生生物, water molds 水霉, even human skeletal muscle 骨胳肌肉 Food Spoilage Food Production Yogurt, pickles, cheese, buttermilk, sour cream,
微生物法检测牛奶中抗生素残留 嗜热链球菌 : 首选菌种
Mucosal 黏膜 delivery of therapeutic and prophylactic 预防疾病 molecules using lactic acid bacteria Nature Reviews Microbiology 6, 349-362 (May 2008) doi:10.1038/nrmicro1840
Homolactic fermentation 同型乳酸发酵 (1 step) EMP 2 lactate only E.g. Lactobacillus delbruckii 德氏乳杆菌
3- 磷酸甘油醛 Heterolactic fermentation 异型乳酸发酵
(2) Alcohol Fermentation 酒精发酵 (2 steps) Only 2 ATP End products: Alcohol + CO 2 Application: Alcoholic beverages, bread dough to rise Found in fungi, yeasts, some bacteria Saccharomyces cerevisiae 酿酒酵母
2. Alcoholic Fermentation Pathway 酒精发酵途径 乙醇 丙酮酸 乙醛
Chinese Liquor
Let microbes work for us! Modify microbes to get novel enzyme or improve its yield. Enzymes from Saccharomyes cerevisiae, S. carlsbergensis 卡氏酵母 disolve thrombus 血栓 to treat heart disease and stroke Pachysolen tannaphilus 管囊酵母 : ferments xylose 木糖 in corn stalk alcohol 40 billion gallons of alcohol to be produced
(3) Mixed - Acid Fermentation 混合酸发酵 Only 2 ATP End products FALSE? Escherichia coli and other enterics 肠道菌
乳酸 甲酸 苹果酸 乙醇 琥珀酸 富马酸 乙酸 Mixed Acid Fermentation (E. Coli)
(4) Propionic Acid Fermentation 丙酸发酵 Only 2 ATP End products: Propionic acid 丙酸 CO 2 Propionibacterium sp. 丙酸菌
Stickland Reaction 由氨基酸发酵产能 A few anaerobic bacteria use AA as C, N and energy source through redox. alanine 丙氨酸 + glycine 甘氨酸 acetic acid 乙酸 + 3NH 3 + CO 2 H donor: ala, leucine 亮氨酸, isoleucine, serine 丝氨酸, phenylalanine 苯丙氨酸, histidine, tryptophan 色氨酸 H acceptor: Gly,ornithine 鸟氨酸,arginine 精氨酸 Clostridium sporogenes 生孢梭菌
Diversity of Fermentation 发酵的多样性 May result in numerous end products 1. Type of organism 微生物种类 2. Original substrate 起始底物 3. Enzymes that are present and active 酶的类型
Diversity of fermentation 酒精发酵同型乳酸发酵异型乳酸发酵同型乙酸异生混合酸发酵 丁酸丁醇发酵己酸盐同型乙酸异生甲醇异生
Aerobic Cellular Respiration 细胞有氧呼吸 It s not toxic to us! e- passed down an ETS with oxygen being the Final Electron Acceptor General equation: Glucose + O 2 CO 2 + H 2 O ATP
Aerobic Cellular Respiration 好氧细胞呼吸 Four subpathways 四段亚途径 1. Glycolysis 2. Transition Reaction 转换反应 3. Kreb s Cycle 三羧酸循环 4. Electron Transport System 电子传递系统
Overview of Cellular Respiration occurring in TWO STAGES 有氧与无氧呼吸代谢的不同场所
2. Transition Reaction 转换反应 Connects Glycolysis to Krebs Cycle End Products: 2 Acetyl CoEnzyme A 乙酰辅酶 A 2 CO 2 2 NADH 2
2. Transition Reaction 转换反应 -Connect glycolysis and TCA
3. Krebs Cycle (Citric Acid) 柠檬酸 ( 三羧酸 ) 循环 Begin and end with citric acid In mitochondrion TCA 循环在线粒体中进行 Acetyl-CoA + 3NAD + +FAD 2CO 2 + 3NADH+FADH 2 +ATP Net yield for one molecule of glucose Prokyrates: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + 38ATP Eukyrates: 36 ATP Function: Produces reducing power under oxidative growth 有氧条件下产生还原力 Under fermentative conditions, the TCA cycle produces intermediates 发酵条件下产生中间代谢产物
TCA Cycle
Question In a bacteria cell, when glycolysis halts, will Kreb cycle stop surely?
4. Electron Transport System 电子传递链 Occurs within the cell membrane 在细胞膜上进行 Chemiosomotic Model of Mitchell 化学渗透模型 34 ATP Oxygen: terminal e - acceptor, produce water 氧为电子最终受体, 与 H+ 和电子形成水 Proton gradient: increases with H + building up 质子梯度增加
Energy release is coupled to the formation of ATP
The eucaryotic mitochondrial process 真核生物线粒体上的电子传递
Electron transport 电子传递 1. Protons: translocated across the membrane, 质子跨膜运输 ( 基质 双层膜空间 ) 2. Electrons: transported along the membrane, 电子经蛋白质载体传输 3. Oxygen: terminal e - acceptor, produce water 氧为电子最终受体, 与 H+ 和电子形成水 4. Proton gradient: increases with H + building up outside, and OH - inside the membrane 质子梯度增加
E. T. of Energy Metabolism: Within the Mito. Inner Membranes 线粒体内膜上的电子传递与能量代谢
Electron transport in Mitochondria 线粒体上的电子传递 Mitochondrial inner membrane
What can be done by using proton motive force Transportation LacY symporter-one proton at a time with one lactose Flagellum rotation 1000 protons for one rotation ATP synthesis 3 protons for one ATP synthesized
Production of ATP by substrate phosphorylation 底物水平磷酸化产生 ATP
ATP production vs cell yield Cell yield is directly proportional to ATP production, so the growth based on fermentation is much more slowly than based on aerobic respiration. 细胞产量与 ATP 产生量正相关, 因此基于发酵的生长远慢于基于有氧呼吸的生长 Medium composition and growth conditions affect cell production via effects on ATP formation efficiency 培养基组成与培养条件可通过影响 ATP 合成的效率而影响细胞的生长.
ATP synthesis in Mitochondria Step 1: Proton gradient built up. 由 NADH 产生的质子在电子传递链上的传递引起线粒体内外膜空间中质子梯度的形成
ATP synthesis in Mitochondria Step 2: Protons enter back into the matrix coupled to ATP synthesis 质子梯度中的质子返回线粒体时推动 ATP 合成
ATP Production from Glucose Oxidation
Total ATP production for the complete oxidation of 1 molecule of glucose in aerobic respiration in prokyrotes ATP Glycolysis 2 Transition Reaction 0 Krebs Cycle 2 E.T.S. 34 Total 38 p.s. Eukyotes: 36 ATP with 2 ATP spent on Acetyl-CoA transference
Energy production by aerobic vs anaerobic - Light of death Swelling of dead body Making holes to let gas out, leaving candle on for 3-4 days
Question If ATP is an essential energy source, why do we need not to add ATP routinely to the growth medium?
Pyruvate can have many fates
Microbiology and World War I
Neuberg vs. Weizmann Carl Neuberg 1915, Chaim Weizmann, Saccharomyces cerevisia 酿酒酵母 Clostridium acetobutylicum 乙酰丁酸梭菌 2 pyruvate acetoacetate 乙酰乙酸 acetone + CO 2 Acetoacetate butyrate butanol
Electron donor energy source Why does everybody need oxygen? Why does a doctor often give weak patients glucose?
Autotrophs 自养生物
Autotrophs 自养生物 Autotrophs: generate organic themselves Photoautotrophs 光能自养生物 Light-dependent in anaerobic mode 依赖光, 厌氧 Glucose reduced both biosynthesis & energy production Photolithotrophic 光能无机营养 & photoorganotrophic 光能有机 Chemoautotrophs 化能自养生物 CO 2 as the C source (same as plants) 碳源是 CO 2 Do not use light (unlike plants) 不使用光源 Energy from chemicals of e- source 电子来源于 : Hydrogen sulfide 硫化氢 Ammonia 氨 Ferrous Iron 亚铁
Chemoautotrophy 化能自养 Also autotrophy 自养生物 :a unique form of metabolism found only in bacteria 仅在细菌中发现 Inorganic compounds are oxidized directly to yield energy 氧化无机物 Requires energy for CO 2 reduction, like photosynthesis 还原 CO 2 需要能量
Chemoautotrophic Communities - Symbiotic 化能自养生物群落 Resistant to High Temp Heavy metal High conc. of H 2 S High acidity: ph < 3 Chemoautotrophic bacteria oxidize H 2 S & CH 4 Quite a lot new varieties!! Tubeworms Clams
Last Supper eaten by bacteria Thiobacillus thioparis 硫杆菌 : SO 2 -- H 2 SO 4 CaCO 3 -------- CO 2 (carbon source) + CaSO 4 (soft) How to control?: antibiotic?
Photosynthesis 光合作用 1. Absorption of light energy 吸收光能 2. Capture of energy in the form of ATP 能量以 ATP 的形式被捕获 3. Synthesis of simple carbon compounds 合成简单碳化合物 6CO 2 + 12H 2 O C 6 H 12 O 6 + 6O 2 + 6H 2 O Light reaction + dark reaction
Cyanobacteria 蓝细菌 (blue-green alga) Used pigments to capture light energy Used H 2 O as e- source (versus FeS or H 2 S) 水作为电子源 Pass e- (energy) to CO 2
Overview of Photosynthesis
1. The Light Reactions: Photophosphorylation 光反应 - 光合磷酸化 1. Chlorophyll 叶绿素 : used by plants, algae, and cyanobacteria to capture e- 2. e- pass through ETC, from which ATP produced by chemiosmosis. 3. When H 2 0 is oxidized, 0 2 is produced 水被氧化产生 0 2
2. The Dark Reactions: The Calvin-Benson Cycle 暗反应 C0 2 fixation: used to synthesize sugars in a light-independent complex cyclic pathway C0 2 被固定合成糖 光依赖的环状反应
Types of Photophosphorylation 光合磷酸化类型 Cyclic photophosphorylation 循环光合磷酸化 e- return to the chlorophyll No oxygen generated Photosynthetic bacteria: Phodosirillales 红螺菌目 Non-cyclic photophosphorylation 非循环光合磷酸化 When H 2 0 is oxidized by, 0 2 is produced Green plants, algae, and cyanobacteria
Cyclic Photophosphorylation 循环光合磷酸化
Comparison between cyclic and non-cyclic photophosphorylation cyclic non-cyclic
Purple Bacteria 紫细菌 Primitive forms of bacteria 原始种类 Contain pigment on membrane 膜上含有色素 : Bacteriorhodopsin 细菌视紫红质 Absorbs light 吸收光 Uses energy to synthesize ATP No organelle to handle photosynthesis Anoxygenic photosynthesis 不产氧光合作用 : unique in bacterial Halophile 好盐菌 : Halobacterium halobium
Bacteriorhodopsin Proton Pump in Halobacterium
Top view of the purple membrane patch. The hexagonal unit cell is displayed in the middle of the patch, surrounded by white line defining the unit-cell dimensions
Connection of Catabolism and Anabolism 分解代谢与合成代谢的联系 Amphibolic Pathway 两用代谢途径 Anaplerotic sequence 代谢回补途径
Versatility of Metabolic Pathways 代谢途径多样性
Connect Catabolism and Anabolism
1. Amphibolic Pathway 两用代谢途径 Citric Acid Cycle: serves both catabolic and anabolic processes regulation Phosphoenolpyruvate (PEP) 磷酸烯醇式丙酮酸 in glycolysis Oxaloacetate 草酰乙酸 in TCA
Glycolysis in amphibolic pathway
TCA in amphibolic pathway 草酰乙酸
2. Anaplerotic Sequence 代谢回补途径 Replenishment Pathway 补偿途径 Glyoxylate cycle 乙醛酸循环 Mostly aerobic 好氧 Key enzymes: Isocitrate lyase 异柠檬酸裂合酶 ICL Malate synthase 苹果酸合成酶 MS 2 pyruvate 丙酮酸 succinate 琥珀酸 +2CO 2
Glyoxylate Cycle 乙醛酸循环 - When fatty acids as sold carbon source - C6 C6 C3 + C2 1:Isocitrate lyase 异柠檬酸裂合酶 2:Malate synthase 苹果酸合成酶 C4 C4 C2 C2 C4 C5 C4
Special Microbial Metabolism Pathways 独特的微生物代谢反应
Special Microbial Metabolism Pathways 1. CO 2 fixation in autotrophy 2. Nitrogen Fixation 3. Synthesis of peptidoglycan 4. Regulation on secondary metabolism
1. Pathways Used to Fix CO 2 I. Ribulose bisphosphate pathway (RuBP) 卡尔文循环, 核酮糖二磷酸途径 II. III. IV. Reductive tricarboxylic acid pathway (rtca) 逆向 ( 还原 ) 三羧酸循环 Reductive acetyl-coa pathway (raca) 厌氧乙酰 CoA 途经 3-Hydroxypropionate cycle 羟基丙酸途径
(I) Calvin Cycle (Ribulose 核酮糖 bisphosphate pathway, RuBP) 卡尔文循环 Most important biosynthetic cycle on earth Both photosynthetic & autotrophs The last step in photosynthesis C 5 + CO 2 + ATP + NADPH ---> C 6 H 12 O 6 Purpose: take energy from photosystem
Calvin Cycle 卡尔文循环 Carboxylation Regeneration Reduction C 5 + CO 2 + ATP + NADPH ---> C 6 H 12 O 6
(II) reductive TCA cycle
(III) Reaction of reductive acetyl CoA pathway 厌氧乙酰 CoA 途径 T: tetrahydrofolate 四氢叶酸, Co: A corrinoid protein 类咕啉 (another type of methyl group carrier)
(IV) The 3-hydroxypropionate cycle 3- 羟基丙酸途径 甲基丙二酰 CoA
2. Biological Nitrogen Fixation 生物固氮
Nitrogen Cycle 氮循环
Biological Nitrogen Fixation 生物固氮 Reaction: N 2 NH 3 amino acid, protein N 2 +8H + +8e - +16ATP 2 NH 3 +H 2 +16ADP +16Pi N 2 fixing organisms: diazotrophs 固氮菌 1. Free-living nitrogen-fixer 自生固氮菌 2. Symbiotic nitrogen-fixer 共生固氮菌 3. Associative nitrogen-fixer 联合固氮菌
Free-living nitrogenfixer 自生固氮菌 1. Obligate anaerobes 专性厌氧菌 : Clostridium pasteurianum 1. Facultative anaerobes 兼性厌氧 : Klebsiella 2. Obligate aerobes 专性好氧 :Azotobacter 固氮菌 3. Photosynthetic bacteria 光合细菌 : Rhodobacter 4. Many cyanobacteria 蓝细菌 5. Some methanogens 产甲烷菌
Symbiotic nitrogenfixer 共生固氮菌 Bradyrhizobium 慢性根瘤菌属 & Rhizobium 根瘤菌属 inhabit root nodules of leguminous 豆科 plants Rhizobium: in a strictly controlled microaerophilic 微需氧 environment. Oxygen:required to generate energy, but too much inactivates nitrogenase 固氮酶
Root Nodule 根瘤 Development of a root nodule
Nitrogen Fixation 固氮 16 ATP needed to convert one N 2 to ammonia!!! Nitrogenase is a relatively slow enzyme
Mechanism of Nitrogen Fixation 固氮机制 Factors Needed for Biological Nitrification 1. ATP supply 2. Reducing power [H] and its transport 3. Nitrogenase 固氮酶 : Found only in anerobic bacteria and cyanobacteria, the only known protein responsible for Nitrification 1. Substrate N 2 2. Mg 2+ 3. Strict anaerobic environment 严格的厌氧环境
Nitrogenase Complex 固氮酶复合物 Made up of two different proteins. MoFe protein,component I, dinitrogenase 固二氮酶 Nitrogenase reductase 固氮酶还原酶 (Fe Protein): component II Two, homodimers 同型二聚体, key component Transfer e - to nitrogenase and bind ATP energy Only takes place in certain anerobic bacteria
Nitrogenase Complex 固氮酶复合物
Nitrogenase MoFe protein,component I, dinitrogenase 固二氮酶 Fe Protein: component II, Nitrogenase reductase 固氮酶还原酶
Electron flow in Nitrogen Fixation Glutamate 谷氨酸
3. Synthesis of Peptidoglycan 肽聚糖合成
1. 前体 Park 核苷酸合成 3. 转肽形成肽聚糖聚合物 2.( 细菌萜醇 ) 单体合成然后易位 Stages of Peptidoglycan Synthesis
O C NH CH CH C S CH 3 O C N CH CH 3 COOH Penicillinase action Breakage of lactam 内酰胺 ring
Selectively toxic for bacteria Bactericidal (killing) 杀菌 Bacteriostatic 抑菌 (growth inhibition) Destroy structures present in bacteria but not in host No harm to patient
Alanine (ala) analog inhibits formation of pentapeptide chain by inhibiting addition of D-ala-D-ala. 1. inhibits conversion of L-ala to D-ala 2. inhibits formation of D-ala-D-ala
Inhibits dephosphorylation inhibits recycling of bactoprenol
Binds to D-ala-D-ala Inhibits cross-linking
Inhibition of peptidoglycan synthesis by antibiotics
4. Synthesis of Secondary Metabolite 次生代谢物的合成
Secondary Metabolite 次生代谢物 Has complex structure 结构复杂 Synthesis via special complicated pathways during later stage with low amount 特殊复杂代谢途径, 产量小 Biological function is not clear 功能不清 Produced from the simple-structured, highly-produced precursor 前体 E.g. pheromone 信息素, toxin, antibiotics
Regulation of Metabolism in Fermentation Removal feedback: Mutant application 营养缺陷型应用 Lysine Fermentation 赖氨酸发酵 IMP Fermentation 肌苷酸发酵 Removal feedback 反馈调节
Lysine Accumulation 赖氨酸积累 add homoserine 高丝氨酸, the prosome 前体 of lysine Mutant Increased lysine yield 苏氨酸蛋氨酸 Engineering gene expression
IMP Fermentation 肌苷酸发酵 Mutant AMP 腺苷酸 Synthesis of the first fully formed purine nucleotide, inosine monophosphate 肌苷一磷酸, IMP begins with 5- phospho-a-ribosyl-1-pyrophosphate, PRPP. Through a series of reactions utilizing ATP, tetrahydrofolate (THF) derivatives, glutamine, glycine and aspartate. The two indicated enzymes (A and B) are those catalyzing the rate limiting step and the reaction necessary for the purine nucleotide cycle, respectively. Using the mutant and adding AMP for growth requirement makes IMP accumulation.
Glutamate Fermentation Change the permeability of cytoplasma 改变膜透性 Addition of Biotin 生物素
Glutamate Fermentation 谷氨酸发酵 - Split pathway with Corynebacterium glutamicum 谷酰胺棒状杆菌 Wild Type dapd Mutant Change the permeability of cytoplasma 改变膜透性 Addition of Biotin 生物素 Use mutant
Metabolic Regulation (Regulation of gene expression) When, where, how much should protein be synthesized?
Regulation of Enzyme Activity 酶活性调节 Feed back inhibition 反馈抑制 Epigenetic 外成性的 modification Post translational modifications Phosphorylation/dephosphorylation 磷酸化 Adenylation/deadenylation 腺苷酰 [ 化 ] 作用
Regulation of Metabolism: feed-back inhibition by the final product 1. Simple feed-back inhibition. The final product (E) inhibits the step from A to B. 2. Co-operative feed-back inhibition. Both final products (D, E) inhibit the first step of their own synthesis together. 3. Multivalent 多价 feed-back inhibition 4. Inhibition at a ramification 分枝式 of a biosynthesis pathway (sequential
Metabolism comparision between prokyote and eukyote What is true for E. col is also true for elephant, only more so Can E. coli cells choose their favored food? Can E. coli learn from its experience? Does E. coli have memory?
Can E. coli cells choose different kinds of foods? If glucose and lactose are both available, E. coli will utilize glucose first. Only after all glucose has been used up, can lactose be used as carbon source
Can E. coli learn from its experience? When E. coli was exposed to phosphate starvation once, next time it responses faster to the same condition
Induction of alkaline phosphatase The induction of AP activity was upon phosphate limitation Faster if the cultures was limited for phosphate previously
Does E. coli have memory? Respond to physical or chemical gradients Directed movement toward or away from the gradient-taxes Chemotaxes Phototaxes Compare sensing along time Temporal gradient response A memory phenomenon
Heat Shock Response 热激反应 / 热休克反应 How does a bacterium know what the temperature is? Heat shock proteins, including a DnaK which is a chaperonin ( molecular chaperones), which helps other proteins fold properly. also involved in the degradation of 32. synthesized amount increased by heat shock. When temperature, DnaK is directed more toward folding proteins and is less available for the degradation of 32.
Quorum Sensing 群体感应 Some prokaryotes have regulatory pathways controlled by the density of cells of their own kind Respond to the signal of other cells of the same species. wide spread among G- bacteria ensure that sufficient cell numbers of a given species are present before eliciting a particular biological response. 确保同一种群数量达到足够时才引发某一反应的机制
Taking bacteria out of causing infections Helen Blackwell 十大美国 科学才子 : 让细菌发抖的人 Novel antibiotics jamming the signal
Key Points 1. Give six fermentation products from pyruvate 2. EMP and TCA pathway and their importance in microorganism 3. Glyoxylate cycle 乙醛酸循环 and its function 4. CO 2 fixation by Calvin Cycle 5. Pathway of biological nitrogen fixation and the main categories of nitrogen-fixing organisms 6. The major steps of peptidoglycan synthesis and give two examples of the inhibitors 7. Homolactic fermentation 同型乳酸发酵 vs Heterolactic fermentation 8. Amphibolic Pathway 两用代谢途径 and Anaplerotic sequence 代谢回补途径