大学微生物英文版.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Chapter 7,Microbial Growth and Growth control,7.1 Overview of Cell Growth,7.2 Population Growth,7.3 Measurement of Growth,7.4 Continuous Culture:The Chemostat,7.5 Effect of Environment on Growth,7.6 Growth Control,7.7 Viral Control,7.8 Fungal Control,第1页,7.1 Overview of microbial growth,The bacterial cell is a synthetic machine that is able to duplicate itself.The synthetic processes of bacterial cell growth involve as many as 2023 chemical reactions of a wide variety of types.Some of these reactions involve energy transformations.Other reactions involve biosynthesis of small molecules-the building,blocks of macromolecules-as well as the various cofactors and coenzymes needed for enzymatic reactions.,第2页,Binary Fission,第3页,6 1.,Microbial Nutrition,Nutrient requirements,Nutritional types of microorganisms,Uptake of Nutrients by the Cell,Culture Medium,Isolation of Pure Cultures,第4页,Microorganisms require about ten elements in large quantities,because they are used to construct carbohydrates,lipids,proteins,and nucleic acids.Several other elements are needed in very small amounts and are parts of enzymes and cofactors.,Concepts:,Nutrient requirements,第5页,Macronutrients,95%or more of cell dry weight is made up of a few major elements:carbon,oxygen,hydrogen,nitrogen,sulfur,phosphorus,potassium,calcium,magnesium and iron.,The first six(C,H,O,N,P and S)are components of carbonhadrates,lipids,proteins and nucleic acids,第6页,Trace Elements,Microbes require very small amounts of other mineral elements,such as iron,copper,molybdenum,and zinc;these are referred to as trace elements.Most are essential for activity of certain enzymes,usually as cofactors.,第7页,Growth Factors,Amino acids are needed for protein synthesis,purines and pyrimidines for nucleic acid synthesis.,Vitamins are small organic molecules that usually make up all or part enzyme cofactors,and only very small amounts are required for growth.,(1)amino acids,(2)purines and pyrimidines,(3)vitamins,第8页,Major nutritional type,Sources of energy,hydrogen/electrons,and carbon,Representative microorganisms,Photoautotroph,(,Photolithotroph,),Light energy,inorganic hydrogen/electron(H/e,-,)donor,CO,2,carbon source,Algae,Purple and green bacteria,Cyanobacteria,Photoheterotroph,(,Photoorganotroph,),Light energy,inorganic H/e,-,donor,Organic carbon source,Purple nonsulfur bacteria,Green sulfur bacteria,Chemoautotroph,(,Chemolithotroph,),Chemical energy source(inorganic),Inorganic H/e,-,donor,CO,2,carbon source,Sulfur-oxdizing bacteria,Hydrogen bacteria,Nitrifying bacteria,Chemoheterotroph,(,Chenoorganotroph,),Chemical energy source(organic),Organic H/e,-,donor,Organic carbon source,Most bacteria,fungi,protozoa,Nutritional types of microorganisms,第9页,Algae,Cyanobacteria,CO,2,+H,2,O,Light,+Chlorophyll,（CH,2,O）+O,2,Purple and green bacteria,CO,2,+2H,2,S,Light,+bacteriochlorophyll,（CH,2,O）+H,2,O+2S,Purple nonsulfur bacteria(,Rhodospirillum,),CO,2,+2CH,3,CHOHCH,3,Light,+bacteriochlorophyll,（CH,2,O）+H,2,O+2CH,3,COCH,3,Photoautotroph:,Photoheterotroph:,第10页,Property,cyanobacteria,Green and purple bacteria,Purple nonsulfur bacteria,Photo-pigment,Chlorophyll,Bcteriochlorophyll,Bcteriochlorophyll,O,2,production,Yes,No,No,Electron donors,H,2,O,H,2,H,2,S,S,H,2,H,2,S,S,Carbon source,CO,2,CO,2,Organic/CO,2,Primary products of,energy conversion,ATP+NADPH,ATP,ATP,Properties of microbial photosynthetic systems,第11页,Chemoautotroph:,Nitrifying bacteria,2 NH,4,+,+3 O,2,2 NO,2,-+2 H,2,O+4 H,+,+132 Kcal,Bacteria,Electron donor,Electron acceptor,Products,Alcaligens and Pseudomonas sp.,H,2,O,2,H,2,O,Nitrobacter,NO,2,-,O,2,NO,3,-,H,2,O,Nitrosomonas,NH,4,+,O,2,NO,2,-,H,2,O,Desulfovibrio,H,2,SO,4,2-,H,2,O.H,2,S,Thiobacillus denitrificans,S,0,.H,2,S,NO,3,-,SO,4,2-,N,2,Thiobacillus ferrooxidans,F,e,2+,O,2,F,e,3+,H,2,O,第12页,are needed to grow microorganisms in the laboratory and to carry out specialized procedures like microbial identification,water and food analysis,and the isolation of particular microorganisms.A wide variety of media is available for these and other purposes.,Culture media,第13页,can be obtained through the use of spread plates,streak plates,or pour plates and are required for the careful study of an individual microbial species.,Pure cultures,第14页,Nutrient molecules frequently cannot cross selectively permeable plasma membranes through passive diffusion and must be transported by one of three major mechanisms involving the use of membrane carrier proteins.,Uptake of nutrients,第15页,1,Phagocytosis,Protozoa,2,Permeability absorption,Most microorganisms,passive transport,simple diffusion,facilitated diffusion,active transport,group translocation,第16页,A few substances,such as glycerol,can cross the plasma membrane by,passive diffusion.,Passive diffusion is the process in which molecules move from a region of higher concentration to one of lower concentration as a result of random thermal agitation.,passive diffusion,第17页,The rate of diffusion across selectively permeable membranes is greatly increased by the use of carrier proteins,sometimes called,permeases,which are embedded in the plasina membrane.Since the diffusion process is aided by a carrier,it is called,facilitated diffusion.,The rate of facilitated diffusion increases with the concentratioti gradient much more rapidly and at lower concentrations of the diffusing molecule than that of passive diffusion,Facilitated diffusion,第18页,Active transport is the transport of solute molecules to higher concentrations,or against a concentration gradient,with the use of metabolic energy input.,Active transport,第19页,Group translocation,第20页,1,Phagocytosis,Protozoa,2,Permeability absorption,Most microorganisms,passive transport,simple diffusion,facilitated diffusion,active transport,group translocation,第21页,A few substances,such as glycerol,can cross the plasma membrane by passive diffusion.Passive diffusion is the process in which molecules move from a region of higher concentration to one of lower concentration as a result of random thermal agitation.,passive diffusion,第22页,The rate of diffusion across selectively permeable membranes is greatly increased by the use of carrier proteins,sometimes called,permeases,which are embedded in the plasina membrane.Since the diffusion process is aided by a carrier,it is called,facilitated diffusion.,The rate of facilitated diffusion increases with the concentration gradient much more rapidly and at lower concentrations of the diffusing molecule than that of passive diffusion,Facilitated diffusion,第23页,The membrane carrier can change conformation after binding an external molecule and subsequently release the molecule on the cell interior.It then returns to the outward oriented position and is ready to bind another solute molecule.,A model of facilitated diffusion,Because there is no energy input,molecules will continue to enter only as long as their concentration is greater on the outside.,第24页,Active transport is the transport of solute molecules to higher concentrations,or against a concentration gradient,with the use of metabolic energy input.,Active transport,第25页,The best-known group translocation system is the,phosphoenolpyruvate:,sugar phosphotransferase system(PTS),which transports a variety of sugars into procaryotic cells while Simultaneously phosphorylating them using phosphoenolpyruvate(PEP)as the phosphate donor.,Group translocation,PEP+sugar(outside)pyruvate+sugar-P(inside),第26页,The phosphoenolpyruvate:sugar phosphotransferase system of,E.coli.,The following components are involved in the system:phosphoenolpyruvate,PEP;,enzyme 1,E I;,the low molecular weight heat-stable protein,HPr;,enzyme 11,E II,-,and enzyme II,I,E III.,第27页,Items,Passive diffusion,Facilitated diffusion,Active transport,Group translocation,carrier proteins,Non,Yes,Yes,Yes,transport speed,Slow,Rapid,Rapid,Rapid,against gradient,Non,Non,Yes,Yes,transport,molecules,No specificity,Specificity,Specificity,Specificity,metabolic energy,No need,Need,Need,Need,Solutes molecules,Not changed,Changed,Changed,Changed,Simple comparison of transport systems,第28页,Mode of action of antibacterial antibiotics,第29页,Symbiosis of peptidoglycan,第30页,6 2.,Microbial growth,The Growth Curve,Cell life cycle,Measurement of Microbial Growth,Measurement of Cell Mass,Growth Yields and the Effects of a Limiting Nutrient,The Continuous Culture of Microorganisms,The Chemostat,The Influence of Environmental Factors on Growth,Outline,第31页,Growth is defined as an increase in cellular constituents and may result in an increase in an organisms size,population number,or both.,When microorganisms are grown in a closed system,population growth remains exponential for only a few generations and then enters a stationary phase due to factors like nutrient limitation and waste accumulation.If a population is cultured in an open system with continual nutrient addition and waste removal,the exponential phase can be maintained for long periods.,Concepts,第32页,3.,A wide variety of techniques can be used to study microbial growth by following changes in the total cell number,the population of viable microorganisms,or the cell mass.,4.Water availability,pH,temperature,oxygen concentration,pressure,radiation,and a number of other environmental factors influence microbial growth.Yet many microorganisms,and particularly bacteria,have managed to adapt and flourish under environmental extremes that would destroy most organisms.,第33页,Growth may be generally defined as a steady increase in all of the chemical components of an organism.Growth usually results in an increase in the size of a cell and frequently results in cell division,Growth definition:,第34页,G,1,Primary growth phase of the cell during which cell enlargement occurs,a gap phase separating cell growth from replication of the genome,S,phase in which replication of the genome occurs,G,2,Phase in which the cell prepares for separation of the replicated genomes,this phase includes synthesis of microtubules and condensation of DNA to form coherent chromosomes,a gap phase separating chromosome replication from miosis.,M,phase called miosis during which the microtubular apparatus is associated and subsequently used to pull apart the sister chromosomes.,Cell life cycle in Eukaryotic cells,G1 S G2 M,G1 R D,Eukaryotic cell:,Prokaryotic cell:,第35页,第36页,Most bacterial cells reproduce asexually by,binary fision,a process in which a cell divides to produce two nearly equal-sized progeny cells.Binary fision involves three processes:,Increase in cell size(cell elongation),DNA replication,Cell division,Binary fision,第37页,Growth curve of bacteria,Lag Phase,Exponential Phase,Stationary Phase,Death Phase,第38页,Growth curve of bacteria,Lag Phase,Exponential Phase,Stationary Phase,Death Phase,第39页,(a),Lag phase:cells begin to synthesize inducible enzymes and use stored food reserves.,(b),Logarithmic growth phase:the rate of multiplication is constant.,(c),Stationary phase:death rate is equal to rate of increase.,(d)Death phase:cells begin to die at a more rapid rate than that of reproduction.,Lag Phase,Stationary Phase,Death Phase,Logarithmic growth phase,第40页,The time required for a cell to divide(and its population to double)is called the generation time.,generation time,Suppose that a bacterial population increases from10,3,cells to 10,9,cells in 10 hours.Calculate the generation time.,Number of cells,Time,N,t,=N,o,x 2,n,N,o,=number of bacteria at beginning of time interval.,N,t,=number of bacteria at end of any interval of time(t).,G=generation time,T=time,usually expressed in minutes,n=number of generation,G=t log2 /log N,t,log N,o,第41页,Chemostat used for continuous cultures.Rate of growth can be controlled either by controlling the rate at which new medium enters the growth chamber or by limiting a required growth factor in the medium.,Continuous culture of microorganisms,Chemostat,第42页,Bacteria grow over a range of temperatures;they do not reproduce below the minimum growth temperattire nor above the maximum growth temperature.Within the temperature growth range there is an optimum growth temperature at which bacterial reproduction is fastest.,Effect of temperature on bacterial growth rate,第43页,Enzymes exhibit a Q,10,so that within a suitable temperature range the rate of enzyme activity doubles for every 10 C rise in temperature.,第44页,Microorganisms are classified as psychrophiles,mesophiles.thermophiles,and extremethemophiles based on their optimal growth temperature.,第45页,Effect of oxygen concentration reduction potential,Effect of oxygen concentration on the growth of various bacteria in,tubes of solid medium,第46页,(a)Obligate aerobes-growth occurs only in the short distance to which the oxygen diffuses into the medium.,(b)Facultative anaerobes growth is best near the surface,where oxygen is available,but occurs throughout the tube.,(c)Obligate anaerobes-oxygen is toxic,and there is no growth near the surface.,(d)Aerotolerant anaerobes-growth occurs evenly throughout the tube but is not better at the surface because the organisms do not use oxygen.,(e)Microaerophiles,aerobic organisms that do not tolerate atmospheric concentrations of oxygen-growth occurs only in a narrow band of optimal oxygen concentration.,第47页,Effect of pH value on microbial growth,Bacteria:Neutral condition,Fungi:Acidic condition,Actinomycetes:Alkaline condition,第48页,Water activity,The water activity of a solution is 1/100 the relative humidity of the solution(when expressed as a percent),or it is equivalent to the ratio of the solutions vapor pressure to that of pure water.,a,w,=P,solution,/P,water,Approximate lower a,w,limits for microbial growth:,0.90 1.00 for most bacteria,most algae and some fungi as,Basidiomycetes,Mucor,Rhizopus,.,0.75 for Halobacterium,Aspergillus,0.60 for some saccharomyces species,第49页,If the concentration of solutes,such as sodium chloride,is higher in the surrounding medium(hypertonic),then water tends to leave the cell.The cell membrane shrinks away from the cell wall(an action called plasmolysis),and cell growth is inhibited.,Plasmolysis,Normal cell,Plasmolyzed cell,第50页,Control of microbial growth,Definitions:,Sterilization,the process of destroying all forms of microbial life on an object or in a material.,Disinfection,the process of destroying vegetative pathogens but not necessary endospores.,Antisepsis,chemical disinfection of skin,mucous membranes or other living tissues,第51页,