Lecture 13 Metabolic Diversity 微生物代谢的多样性

School of Life Science and BiotechnologyShanghai Jiao Tong Universityhttp://micro.sjtu.edu.cn

Chapter 17 inBROCK BIOLOGY OF MICROORGANISMS

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I. The Phototrophic Way of Life

Energy source-light • Photosynthesis- conversion of light energy to

chemical energy光合作用: 将光能转化为化学

能的过程

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Figure: 17-01

Carbon source-photoautotroph -CO2光能

自养型

photoheterotroph-organic carbon光能异养型

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13.1 Photosynthesis 光合作用

Green plants, algae, andGreen plants, algae, and cyanobacteriacyanobacteria use H2O as a source of reducing power to reduce NADP+ to NADPH and produce O2 as a by-product.绿色植物,藻类,蓝细菌以水为电子供体,产生O2为副产物. Some Some phototrophicphototrophic bacteriabacteria obtain reducing power from other electron donors, typically reduced sulfur sources (H2S, S0, S2O3

2-) or H2.某些光合细菌以

还原性硫化物或氢为电子供体

oxygenic phototrophs产氧光合生物 , light drives the oxidation of water to oxygen.

Fig.17.2b

Figure: 17-02a

anoxygenic phototrophs不产氧光合生物: obtain their energy from light (hv). They do not produce O2.

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13.2 Photosynthetic pigments and their location within the cell光合色素及其细胞内定位

Chlorophyll-Magnesium containing porphyrin叶绿素:含镁的卟啉

• Cyanobacteria-chlorophyll a叶绿素a• Purple bacteria-bacteriochlorophyll a 菌绿素a

环戊酮环戊酮

Differences between chlorophyll a and bacteriochlorophyll a

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Fig. 17.3 Structure and spectra of chlorophyll a. it shows strong absorption of red light (680nm) and blue light (430nm).

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Fig 17.3 Structure and spectra of bacteriochlorophyll a.it shows strong absorption at 870, 800, 590, and 360 nm.

Shanghai Jiao Tong University Figure 17.4 Structure of known bacteriochlorophylls.The differentsubstituents present in the positions R1 to R7 are given in the accompanying table.

Bacteriochlorophyll diversity 细菌叶

绿素的多样性

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Chlorophyll diversity and its ecological significance 色素多样性的生态优势

A strategy to make better use of the energy of the electromagnetic spectrum.可更充分地利用电磁光

谱的能量

• Different pigments using light with different wavelength ⇒• Unrelated bacteria/organisms coexisting in the same habitat,

each using wavelengths of light that the other is not using.

p.534-535

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Photosynthetic apparatus: Photosynthetic membrane and Chloroplasts 光合膜与叶绿体

Chloroplast in eukaryotes真核生物: 叶绿体

Prokaryotes• Purple bacteria-invagination of the cytoplasmic

membrane紫细菌

• Heliobacteria-cytoplasmic membrane螺旋杆菌

• Green bacteria-cytoplasmic membrane and chlorosomes绿细菌

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Arrangement of bacteriochlorophyllmolecules 菌绿素分子的排列

in the photosynthetic membrane 50-300 bacteriochlorophyll molecules form a complex Most pigment molecules are antenna molecules for light harvesting• A small number are reaction center molecules

Harvesting light under low light intensities• Chlorosome in green sulfur bacteria and green nonsulfur

bacteria

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13.3 Accessory pigments其它色素

Carotenoids play primarily a photoprotective role类胡萝卜素起光保护作用

Phycobilins function in light-harvesting藻胆素起

光采集作用

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13.4 Anoxygenic Photosynthesis:purple bacteria as example 不产氧光合作用

Photosynthetic apparatus of purple phototrophic bacteria: four membrane-bound pigment-protein complexes and ATPase• Reaction center• Light harvesting I• Light harvesting II• Cytochrome bc1 complex• ATPase

Fig.17.14 Electron flow inanoxygenic photosynthesis in a purple bacterium. (Cyclic electron flow). Light energy converts a weak electron donor, P870, into a very strong electron donor, P870*. The remaining steps in photosynthetic electron flow are much the same as that of respiratory electron flow.

RC, reaction center; Bchl, bacteriochlorophyll; Bph, bacteriopheophytin; QA, QB, intermediatequinones; Q pool, quinone pool in membrane;Cyt, cytochrome

Thermodynam

ic gradient

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13.4.1 ATP formation of anoxygenic photosynthesis in purple bacteria

Photophosphorylation光合磷酸化

• Synthesis of ATP during electron flow occurs as a result of the formation of a proton motive forceand the activity of ATPase.ATP的产生:质子动

势形成及ATP酶

Cyclic photophosphorylation环式光合磷酸化

• Electrons are repeatedly moved around a closed circle.

• There is no net input or consumption of electrons

Shanghai Jiao Tong University Cyclic photophosphorylation环式光合磷酸化Electrons are repeatedly moved around a closed

circle. There is no net input or consumption of electrons

Fig.17.15

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13.4.2 Autotrophy in Purple Bacteria: Electron donors自养紫细菌的电子供体

Reducing power (NADH) must be made so that CO2 can be reduced to the level of cell material.Electron donors from environment

• Reduced sulfur source-H2S, S0, S2O32-

• H2

• Fe2+

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.

Reverse electron flow to produce NAD(P)H

Electrons from the quinonepool must be forced against the thermodynamic gradient to reduce NAD+ to NADH反向电子流：电子必须逆热力

学梯度转移给NAD+

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13.5 Oxygenic photosythesis 产氧光合作用

Electron flow in oxygenic phototrophs involves two distinct, but interconnected, photochemical systems (photosystem Iand photosystem II). 产氧光合作用包括两个光合系统

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Fig 17.19 Electron flow in oxygenic photosynthesis, the “Z” scheme. Twophotosystems (PS) are involved, PS I and PS II. P680 and P700 are the reaction center chlorophylls of PS II and PS I, respectively.

Ph, Pheophytin; Q, quinone; Chl, chlorophyll a; Cyt, cytochrome; PC,plastocyanin; FeS, nonheme iron-sulfur protein; Fd, ferredoxin; Fp, flavoprotein;

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An electron from water is donated to the oxidized P680molecule following the absorption of a quantum of light. Later the electron is accepted by the P700of PSI, which has previously absorbed light quanta and begins the steps that lead to the reduction of NADP+.来自水的电子供给P680, 然后再交给P700,由它开始NADP+的还原过程。

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13.5.1 ATP Synthesis in Oxygenic Photosynthesis

ATP was generated by noncyclic photophosphorylation.非环式光合

磷酸化产生ATP.• Electrons whose transport

results in ATP formation do not cycle back to reduce the oxidized P680, they are used in the reduction of NADP+

(reducing power). 电子在ATP形成过程中不流回到氧化态

P680,而用于形成还原力

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13.5.2 Anoxygenic photosynthesis in oxygenic phototrophs 产氧光合生物的不产氧光合作用

When sufficient reducing power is present, ATP can also be produced in oxygenic phototrophs by cyclic photophosphorylation involving only PSI.当还原力充足

时,ATP也可通过PS1的环

式光合磷酸化产生.

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13.6 Autotrophic CO2 fixation: The Calvin cycle卡尔文循环固定CO2

What does a cell require to convert CO2 into fructose in the Calvin cycle?

• NAD(P)H (reducing power)• ATP (energy)• Two key enzymes

• Ribulose biphosphate carboxylase (RubisCO)二磷酸核酮糖羧化酶

• Phosphoribulokinase磷酸核酮糖激酶

Detail

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13.7 Autotrophic CO2 fixation: Reverse Citric Acid Cycle and the Hydroxypropionate Cycle

Reverse Citric Acid Cycle presents in green sulfur bacteria Chlorobium.绿硫细菌的绿菌属:反向三羧酸循

环

Hydroxypropionate Cycle presents in green nonsulfur bacteria Chloraflexus. 绿色非硫菌的绿屈挠菌属:羟基

丙酸循环

Detail

Figure: 17-24a

The reverse citric acid cycle反向三羧酸循环

Ferredoxinred indicates carboxylation reactions requiring reduced ferredoxin (2 H each). Reduced ferredoxin is generated in Chlorobium by light-driven reactions. Starting from oxalacetate, each turn of the cycle results in three molecules of CO2 being incorporated and pyruvate as the product. The cleavage of citrate by the ATP-dependent enzyme citrate lyase regenerates the C4 acceptor oxalacetate and produces acetyl-CoA for biosynthesis.

The hydroxypropionate pathway羟基丙酸途径

Figure: 17-24b

Acetyl-CoA is carboxylated twice to yield methylmalonyl-CoA甲基丙二酰CoA. This intermediate is rearranged to yield acetyl-CoAand glyoxylate乙醛酸. The latter is converted to cell material probably through a serine or glycine intermediate.

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