《微生物学》课件 microbiology Chapter 3

1、Chapter 3Nutritional Types and Energy production 3.1 Nutritional Requirements1.1 Source of Energy All microorganisms require a source of energy. Some rely on chemical compounds for their energy and are designated(指定) as chemotrophs.化能营养生物Others can utilize radiant energy (light) and are called photo

2、trophs. 光能营养生物3.1.2 Source of electronsAll microorganisms require a source of electrons for their metabolism. Some can use reduced inorganic compounds as electron donors and are termed lithotrophs无机营养型. Others use organic compounds as electron donors and are called organotrophs有机营养型.3.1.3 Carbon sou

3、rceAll microorganisms require carbon in some form for use in synthesizing cell components. All require at least small amount of CO2. However, some can use CO2 as their major, or even sole, source of carbon; 3.1.3 Carbon sourcesuch microorganisms are termed autotrophs自养生物. Others require organic comp

4、ounds as their carbon source and are termed heterotrophs异养生物.3.1.4 Nitrogen sourceAll microorganisms require nitrogen in some form for cell components. Bacteria are extremely versatile in this aspect. Unlike eucaryotes, some bacteria can use atmospheric nitrogen. 3.1.4 Nitrogen sourceOthers thrive o

5、n inorganic nitrogen无机氮compounds such as nitrate硝酸盐, or ammonium salts铵盐, and still others derive nitrogen from organic compounds such as amino acids. 3.1.5 MacronutrientsPhosphorus occurs in nature in the form of organic and inorganic phosphates and is required by the cell for synthesis of nucleic

6、acids and phospholipids.Sulfur is required because of its structural role in the amino acids cysteine(半胱氨酸, 巯基丙氨酸) and methionine(甲硫氨酸) and because it is present in a number of vitamins, such as thiamine(硫胺/维生素B1), biotin, as well as in coenzyme A. Sulfur undergoes a number of chemical transformatio

7、ns in nature carried out by microorganisms ( biogeochemical cycle )Potassium is required by all organisms. A variety of enzymes, including some of those involved in protein synthesis, specifically require potassium.Magnesium镁functions to stabilize ribosomes, cell membranes, and nucleic acids, and is

8、 also required for the activity of many enzymes.Calcium helps stabilize the bacterial cell wall and plays a key role in the heat stability of endospores.Sodium钠is not required by all microorganisms, but certain marine bacteria, cyanobacteria, and photosynthetic bacteria do require it. For those memb

9、ers of archaea known as the “ extreme halophiles”, the requirement is astonishing. They can not grow with less than 1217% NaCl. They require this high level of NaCl for maintenance of their cell walls and for the stability and activity of their certain enzymes. Iron plays a major role in cellular re

10、spiration, being a key component of the cytochromes细胞色素类and iron-sulfur proteins involved in electron transport.3.1.6 Micronutrients, trace elementsAlthough required in just tiny amounts, Micronutrients are just as critical to cell function as are macronutrients. Micronutrients are metals, many of w

11、hich play a structural role in various enzymes.Because the requirement for trace elements is so small, for the laboratory culture of microorganisms it is frequently unnecessary to add trace elements to the culture medium. However, if a culture medium contains highly purified chemicals dissolved in h

12、igh purity distilled water, a trace element deficiency can occur. In such cases a small amount of solution of trace metals is added to the medium to make available the necessary metals.3.1.7 Growth factorsGrowth factors are organic compounds that, like micronutrients, are required in very small amou

13、nts and only by some cells. Growth factors include vitamins, amino acids, purines, and pyrimidines. 3.1.7 Growth factorsAlthough most microorganisms are able to synthesize all of these compounds, some microorganisms require one or more of them preformed from the environment.Vitamins are the most com

14、monly needed growth factors. Most vitamins function as parts of coenzymes. Many microorganisms are able to synthesize all the components of their coenzymes, but some are unable to do so and must be provided with certain parts of these coenzymes in the form of vitamins. B1的辅酶形式TPP，是丙酮酸脱羧酶和-酮 戊二酸脱羧酶的辅

15、酶，参与-酮酸的氧化脱 羧。另外还是转酮酶的辅酶，参与糖代谢。维生素B2是FMNFAD的组成成分，FMN和FAD是脱氢酶的辅酶。B5是NAD和NADP的组成成分，NAD和NADP是许多脱氢酶的辅酶，参与递氢。维生素C是羟化酶的辅酶，参与体内的多种羟化作用。 如促进胶原蛋白和粘多糖的合成 ，维持细胞间质的完 整，促进伤口愈合。缺乏维生素C引起毛细血管出血，造成坏血病。Lactic acid bacteria are renowned for their complex vitamin requirement. The vitamins most commonly required by micr

16、oorganisms are B1,B6, B12, and biotin.3.1.8 WaterAll microorganisms require water. Nutrients must be in aqueous solution before they can enter the cells. Water is to dissolve and disperse nutrients and to provide a suitable milieu for the various metabolic reactions of a cell. 3.1.8 WaterMoreover, t

17、he high specific heat of water provides resistance to sudden, transient temperature changes in the environment.3.2 Nutritional Types of MicroorganismsAlthough microorganisms have great diversity of nutritional requirement, they can be divided into four major groups on the basis of their utilization

18、of energy and carbon sources. 3.2.1 Photolithotroph光能无机营养菌or photoautotrophThey utilize light as energy source, and CO2 as major or even sole source of carbon.3.2.2 Photoorganotroph or photoheterotrophThey require light as energy source and organic compounds as carbon source.3.2.3 Chemolithotroph or

19、 ChemoautotrophThey rely on inorganic chemical compounds for their energy and use CO2 as their major, or even sole source of carbon. 3.2.4 Chemoorganotroph or ChemoheterotrophThey utilize organic compounds as their energy and carbon Source. Most bacteria and all fungi belong to this group. Major nut

20、ritional typeSources of energy,hydrogen/electrons, and carbonRepresentative microorganismsPhotoautotroph (Photolithotroph)Light energy, inorganic hydrogen/electron(H/e-) donor, CO2 carbon sourceAlgae, Purple and green bacteria, CyanobacteriaPhotoheterotroph (Photoorganotroph)Light energy, inorganic

21、H/e- donor, Organic carbon sourcePurple nonsulfur bacteria, Green sulfur bacteriaChemoautotroph(Chemolithotroph)Chemical energy source (inorganic), Inorganic H/e- donor, CO2 carbon sourceSulfur-oxdizing bacteria, Hydrogen bacteria,Nitrifying bacteriaChemoheterotroph(Chenoorganotroph) Chemical energy

22、 source (organic), Organic H/e- donor, Organic carbon sourceMost bacteria, fungi, protozoaNutritional types of microorganismsAlgae, CyanobacteriaCO2 + H2O Light + Chlorophyll （CH2O） +O2Purple and green bacteriaCO2 + 2H2S Light + bacteriochlorophyll （CH2O） + H2O + 2SPurple nonsulfur bacteria (Rhodosp

23、irillum)CO2 + 2CH3CHOHCH3 Light + bacteriochlorophyll （CH2O） + H2O + 2CH3COCH3Photoautotroph:Photoheterotroph:PropertycyanobacteriaGreen and purple bacteriaPurple nonsulfur bacteriaPhoto - pigmentChlorophyllBcteriochlorophyllBcteriochlorophyllO2 productionYesNoNoElectron donorsH2OH2, H2S, SH2, H2S,

24、SCarbon sourceCO2CO2Organic / CO2Primary products of energy conversionATP + NADPHATPATPProperties of microbial photosynthetic systemsChemoautotroph:Nitrifying bacteria2 NH4+ + 3 O2 2 NO2- + 2 H2O + 4 H+ + 132 KcalBacteriaElectron donorElectron acceptorProductsAlcaligens and Pseudomonas sp.H2O2H2ONit

25、robacterNO2-O2NO3- , H2ONitrosomonasNH4+O2NO2- , H2ODesulfovibrioH2SO4 2-H2O, H2SThiobacillus denitrificansS0. H2SNO3-SO4 2- , N2Thiobacillus ferrooxidansFe2+O2Fe3+ , H2O3.3 Medium, Media or culture mediaum, culture media3.3.1 definition: an aqueous solution containing various nutrients suitable for

26、 the growth of microorganisms.3.3.2 Types of media3.3.2.1 Based on the chemical compositionSynthetic mediaThe chemical composition of every ingredients in the medium is clear.Medium for cultivation of Actinomycetes放线菌Starch 20g KNO3 1.0g K2HPO4 0.5gMgSO47H2O 0.5g NaCl 0.5g FeSO47H2O 0.01g dH2O 1000m

27、lNatural mediaThe media containing complex natural raw materials such as peptones, meat broth, yeast extract, plants and animal materials.Medium for cultivation of fungi Potato 200g sucrose 20g H2O 1000ml Natural mediaMedium for cultivation of bacteria Beef extract牛肉膏5.0g peptone 10.0g NaCl 5.0g H2O

28、 1000ml3.3.2.2 Based on physical statusliquid media : Broth media 肉汤Semisolid media: Agar concentration is 0.20.5%3.3.2.2 Based on physical statusSolid media: The solidifying agent凝固剂is added to the liquid media. The solidifying agent is usually agar, which at concentrations of 1.52.0% forms firm, t

29、ransparent gels that are not degraded by most bacteria. 3.3.2.2 Based on physical statusSilica gel is sometimes used as an inorganic solidifying agent for cultivation of autotrophic bacteria.3.3.2.3 Based on special purposeSelective mediaThese media provide nutrients that enhance the growth of a par

30、ticular type of microorganism and do not enhance (and may even inhibit) other types of microorganisms that may be present. 3.3.2.3 Based on special purposeSelective mediaFor instance, nitrogen-free medium (Ashby) will specifically select the growth of nitrogen-fixing bacteria.Glucose 10g k2HP04 0.2g

31、 MgSO4.7H2O 0.2g NaCl 0.2g K2SO4 0.2g CaCO3 5.0g H2O 1000ml Enriched mediaThese media contain a certain nutrient that promotes and enriches a special type of microorganism. For example, a medium in which cellulose is the only carbon source will enrich the growth of cellulose-utilizing microorganism.

32、 During the process of cultivation, the noncellulose-utilizing microorganisms are eliminated gradually. This is especially useful for isolation of a bacterium when the number is very low in the sample.Differential mediaThe media that contain some kinds of ingredients which can differentiate various

33、kinds of microorganisms. For example, if a mixture of bacteria is inoculated接种onto a blood-containing agar medium, some of the bacteria may hemolyze the red blood cells; others do not. Thus one can distinguish between hemolytic and nonhemolytic bacteria on the same medium.3.3.3 Preparation of media3

34、.3.3.1 The principlesThe nutrients in the medium with suitable concentration and ratio must satisfy the normal growth of microorganisms.Optimum pH for growthIn large scale production, the source and price of the ingredients in the medium must be considered.氮源过多，会使菌体生长过于旺盛，pH偏高，不利于代谢产物的积累，氮源不足，则菌体繁殖量

35、少，从而影响产量。碳源过多，则容易形成较低的pH，若碳源不足，易引起菌体衰老和自溶。另外碳氮比不当还会影响菌体按比例地吸收营养物质，直接影响菌体的生长和产物的形成。菌体在不同的生长阶段，其对碳氮比的最适要求也不一样。 3.3.3.2 The proceduresEach ingredient with correct amount is dissolved in the appropriate volume of distilled H2O;The pH of the fluid medium is determined with a pH meter and adjusted if nece

36、ssary;3.3.3.2 The proceduresIf a solid medium is desired, agar is added and the medium is boiled to dissolve the agar;The medium is sterilized, generally by autoclaving. Some specific ingredients that are heat-labile（热不稳定） are sterilized by filtration.3.4 Transport of nutrients3.4.1 Passive diffusio

37、n被动扩散,简单扩散Passive diffusion is the process that solute molecules cross the membrane as a result of a difference in concentration浓度差 of the molecules across the membrane. 3.4.1 Passive diffusionThe difference in concentration ( higher outside the membrane than inside) governs the rate of inward flow

38、of the solute molecule. With time, this concentration gradient浓度梯度diminishes until equilibrium is reached.Except for water and some lipid-soluble molecules, few compounds can pass through the cytoplasmic membrane by passive diffusion. In passive diffusion, no substance in the membrane interacts spec

39、ifically with the solute molecule, and energy is not needed. Passive diffusion is the net movement of small molecules or ions from an area of higher concentration to an area of lower concentration. Diffusion is powered by the potential energy of a concentration gradient and does not require the expe

40、nditure of metabolic energy. Examples include the transport of oxygen and carbon dioxide（CO2） into and out of cells. Osmosis is the diffusion of water across a membrane from an area of higher water concentration (lower solute concentration) to lower water concentration (higher solute concentration).

41、 Osmosis is powered by the potential energy of a concentration gradient and does not require the expenditure of metabolic energy. . 微生物的营养和代谢Free Water Passing Through Membrane Pores When a solute such as sugar dissolves in water, it forms weak hydrogen bonds with water molecules. While free, unboun

42、d water molecules are small enough to pass through membrane pores, water molecules bounded to solute are not. . 3.4.2 Facilitated diffusion促进扩散This process is similar to passive diffusion in that the solute molecule also flows from a higher to lower concentration. But it is different from passive di

43、ffusion because it involves a specific protein carrier molecule called permease渗透酶 located in the cytoplasmic membrane. The carrier molecule combines reversibly with the solute molecule, and the carrier-solute complex moves between the outer and inner surfaces of the membrane, releasing one solute m

44、olecule on the inner surface and returning to bind new one on the outer surface.3.4.2 Facilitated diffusionThis type of transportation is common in eukaryotic cells. Sugars enter them by this way.No ATP is needed. There is specific interactions between the solute and protein carrier in the membrane.

45、The transport of substances across a membrane by protein transporters (also called carrier proteins) from areas of higher concentration to lower concentration. No energy is required. the transport of substances across the membrane by means of uniporters. Transport of Substances Across a Membrane by

46、UniportersPassive Transport of Substances Across a Membrane 3.4.3 Active transportAlmost all solutes are taken up by cells through active transport. The three steps of active transport are:Binding of solute to a receptor site on a membrane-bound carrier protein.Translocation of the solute-carrier co

47、mplex across the membrane.Carrier protein release solute to the cell interior。3.4.3 ACTIVE TRANSPORTThe cell uses transporter proteins (carrier molecules, antiporters or symporters ) and energy from a proton motive force质子动力势or the breakdown of ATP to transport substances across a membrane against t

48、he concentration gradient. Active transport allows cells to accumulate needed substances even when the concentration is lower outside.An example of an ATP-dependent active transport found in various gram-negative bacteria is the ATP-binding cassette (ABC) system. This involves substrate-specific bin

49、ding proteins located in the bacterial periplasm, the gel-like substance between the bacterial cell wall and cytoplasmic membrane. Active Transport, Step 1 This form of active transport involves both transporter proteins and the energy provided by the hydrolysis of ATP. A specific periplasmic-bindin

50、g protein carries the substance to be transported to a membrane-spanning transporter. Active Transport, Step 2 The molecule to be transported across the membrane enters the transporter protein system and a molecule of ATP enters the ATP binding site of the ATP-hydrolyzing protein. Active Transport,

51、Step 3Energy provided by the hydrolysis of ATP into ADP, phosphate, and energy moves the molecule across the membrane. Active Transport, Step 4The carrier protein releases the molecule being transported and the transporter system is ready to be used again.Active Transport of Substances Across a Memb

52、rane:The ATP-Binding Cassette Transport System In the ATP-binding cassette (ABC) system of transport, a high affinity binding protein located in the periplasm between the cytoplasmic membrane and the cell wall picks up the substance to be transported and carries it to the membrane spanning transport

53、er. The actual transport across the membrane is powered by the energy provided by the breakdown of ATP by an ATP-hydrolyzing protein 3.4.4 Group translocationGroup translocation is the process in which the solute is chemically altered in the course of passage across the membrane.3.4.4 Group transloc

54、ationA high-energy phosphate group from phosphoenolpyruvate (PEP) is transferred by a series of enzymes to glucose. The final enzyme both phosphorylates（磷酸化） the glucose and transports it across the membrane as glucose 6-phosphate. Group TranslocationA special form of active transport that can occur

55、 in prokaryotes. A substance is chemically altered during transport across a membrane so that once inside, the membrane becomes impermeable（不能渗透的） to that substance and it remains within the cell. An example of group translocation in bacteria is the phosphotransferase system. A high-energy phosphate

56、 group from phosphoenolpyruvate (PEP) is transferred by a series of enzymes to glucose. The final enzyme both phosphorylates the glucose and transports it across the membrane as glucose 6-phosphate. Group Translocation, Step 1When bacteria use the process of group translocation to transport glucose

57、across their membrane, a high-energy phosphate group from phosphoenolpyruvate (PEP) is transferred to the glucose molecule to form glucose-6-phosphate Group Translocation, Step 2A high-energy phosphate group from PEP is transferred to the glucose molecule to form glucose-6-phosphate. Group Transloca

58、tion, Step 3The glucose-6-phosphate is transported across the membrane.Group Translocation, Step 4Once the glucose has been converted to glucose-6-phosphate and transported across the membrane, it can no longer be transported back out. Group Transport of Substances Across a Membrane: Group Transloca

59、tionA high-energy phosphate group from phosphoenolpyruvate (PEP) is transferred by a series of enzymes to glucose. The final enzyme both phosphorylates the glucose and transports it across the membrane as glucose 6-phosphate. Active Transport of Substances Across a Membrane:Group TranslocationGroup

60、translocation and active transport require energy and accumulate substrates against concentration gradient. Solutes can be concentrated within the cell several thousand times greater than outside the cell. There is specific interaction between the solute and protein carrier in the membrane. ItemsPas