《微生物学》双语教学授课教案授课教师：李淑彬华南师范大学生命科学学院2003.21
1 《微生物学》双语教学 授课教案 授课教师：李淑彬 华南师范大学生命科学学院 2003.2
Chapter1Theintroductionofmicrobiology第1章绪论Microbiology（微生物学）：Microbiology isspecializedarea ofbiologythatdealswithlivingthingsordinarily too small tobe seen with the naked eyes.Microorganisms（微生物，microbe）：Microorganismsare defined as the organisms that areso small that,normally,it cannot be seen without the use of a mocriscope.Theword isthereforeusedtodescribevirus,bacreria,fungi,protozoomandsomealgaeBacteria(细菌）：Bacteria are some small,single celle organisms.Because theyhaveno nucleus,the cells are described as prokaryotes.Fungi（真菌）：Fungi（mushrooms（蘑菇），molds（霉菌），andyeasts）haveeukaryotic（真核的）cells (with a true nucleus).Most fungi are multicellular.Fungi obtain nutrients byabsorbing organic material from their environment.Protozoom(原生动物)：Protozoans are unicellular eucaryotes and are classified according totheir means of locomotion. Protozoans obtain nourishment by absorption or ingestion throughspecialized structures.Algae （藻类)：Alage are unicellular ormulticellular eukaryotes that obtain nourishment byphotosynthesis.Algae produce oxygen and carbohydrates that are used by other organisms.Viruses（病毒)：Viruses arenoncellular entitiesthatareparasites ofcells.Virusesconsist ofanucleicacid core(DNAor RNA) surrounded by a protein coat. An envelope may surround the coatAbrief history ofmicrobiologyThe scienceof microbiology did not start until the invention of the microscope in the mid16th century and it was not until the late 17th century that Antoine van Leeuwenhoek madetheir first records offungi, bacteria and protozoa.The late 19th century was the time when the first real breakthroughs on the role of microbesin the environment and medicine were made. Louis Pasteur disproved the theory ofspontaneous generation（自然发生）（that living organisms spontaneously arose frominorganic material) and Robert Koch's development of pure culture techniques allowed him toshowunequivocally that a bacterium was responsible for a particular disease. Sincethen thescience has grown dramatically as microbiology impinges on all aspects of life and theenvironment.2.Louis Pasteur stated that microorganisms are in the air everywhere and offered proof ofbiogenesisLouisPasteurdiscoveriesledtothe developmemt of aseptic（无菌的）techniques used in laboratory and medical procedures to prevent contamination bymicroorangisms that are in the air.Louis Pasteur found that yeast ferments（发酵）sugarto alchhol and that can oxidize alcohol to acetic acid.A heating process called pasteurization（巴斯德消毒）isusedtokillbacteriainsomealcoholbeveragesandmilks.JosephListerintroducedtheuseofadisinfectant（消毒）tocleansurgicaldressings inordertocontrolinfections in humans.Robert Koch proved that microorganisms transmit diseases.He used asequenceofprocedures calledKoch'spostulates（科赫法则）Whichareused todayto provethat a particular microorganism casues a particular disease.Koch's postulates:2
2 Chapter1 The introduction of microbiology 第 1 章绪论 Microbiology（微生物学）：Microbiology is specialized area of biology that deals with living things ordinarily too small to be seen with the naked eyes. Microorganisms（微生物，microbe） ：Microorganisms are defined as the organisms that are so small that ,normally,it cannot be seen without the use of a mocriscope. The word is therefore used to describe virus,bacreria,fungi,protozoom and some algae. Bacteria(细菌) ：Bacteria are some small,single celle organisms. Because they have no nucleus, the cells are described as prokaryotes. Fungi(真菌)：Fungi (mushrooms（蘑菇）, molds（霉菌）, and yeasts) have eukaryotic（真 核的） cells (with a true nucleus). Most fungi are multicellular.Fungi obtain nutrients by absorbing organic material from their environment. Protozoom(原生动物)：Protozoans are unicellular eucaryotes and are classified according to their means of locomotion. Protozoans obtain nourishment by absorption or ingestion through specialized structures. Algae（藻类）：Alage are unicellular or multicellular eukaryotes that obtain nourishment by photosynthesis.Algae produce oxygen and carbohydrates that are used by other organisms. Viruses（病毒）：Viruses are noncellular entities that are parasites of cells. Viruses consist of a nucleic acid core (DNA or RNA) surrounded by a protein coat. An envelope may surround the coat. A brief history of microbiology The science of microbiology did not start until the invention of the microscope in the mid 16th century and it was not until the late 17th century that Antoine van Leeuwenhoek made their first records of fungi, bacteria and protozoa. The late 19th century was the time when the first real breakthroughs on the role of microbes in the environment and medicine were made. Louis Pasteur disproved the theory of spontaneous generation（自然发生）(that living organisms spontaneously arose from inorganic material) and Robert Koch's development of pure culture techniques allowed him to show unequivocally that a bacterium was responsible for a particular disease. Since then the science has grown dramatically as microbiology impinges on all aspects of life and the environment. 2. Louis Pasteur stated that microorganisms are in the air everywhere and offered proof of biogenesisLouis Pasteur ˊdiscoveries led to the developmemt of aseptic（无菌 的 ） techniques used in laboratory and medical procedures to prevent contamination by microorangisms that are in the air.Louis Pasteur found that yeast ferments（发酵） sugar to alchhol and that can oxidize alcohol to acetic acid.A heating process called pasteurization （巴斯德消毒）is used to kill bacteria in some alcohol beverages and milks.Joseph Lister introduced the use of a disinfectant（消毒） to clean surgical dressings in order to control infections in humans.Robert Koch proved that microorganisms transmit diseases.He used a sequence of procedures called Koch’s postulates（科赫法则）,Which are used today to prove that a particular microorganism casues a particular disease.Koch’s postulates：
Koch's postulates are a number of criteria that have been used in the past to prove that abacterium is responsible for a particular disease.1.Thebacteria should befound inall casesand atall sites ofthedisease2.Thebacteria should be isolated fromtheinfected person and maintained in pure culture3.The pure cultured microbe should cause symptoms of the disease on inoculation intoasusceptible individual4.Thebacteria should be reisolated fromthe intentionally infected hostThe importance of microbiology:microbes in our body1.EveryonehasmicroorganismsinandonthebodySomemicroorganisms liveinhumansandotheranimalsand are needed tomaintain theanimals health.thesemake upthenormal flora（正常菌群），2.Some Microorganisms cause disease.3. The disease-producing properties of a species of microbe and the host's resistance areimportant factors in determining whether a person will contract a disease.2.MicrobesandHumanWelfare1. Microorganisms degrade dead plants and animals and recycle chemical elements to beused by living plants and animals.2.Bacteria areused to decompose organic matter in sewage.Bioremediation processes usebacteriatocleanuptoxicwastes.3. Bacteria that cause diseases in insects are being used as biological controls of insect pests.Biological controlsarespecific forthepestanddonotharmtheenvironment.4.Usingrecombinant DNA,bacteria canproduce importanthuman proteins,suchas insulinbeta-endorphin,and hepatitis B vaccine.Microorganisms can be used to help producefoods. They are also food sources (single-cell protein) themselves.3.As a basic biological science:microorganisms are the best model systems for understandingbasic lifeprocesses.All cells have much in common, what is truefor E. coli is also truefor elephant, only moreSOSimple yet representativeEasiness and quickness to growlargequantityCommon characterizesof microorganism·Big surface/volume·High absorption and transformation·Rapid growth and reproductionEasiness to variation·high adaptation to environment·DiversityReview question3
3 Koch's postulates are a number of criteria that have been used in the past to prove that a bacterium is responsible for a particular disease. 1. The bacteria should be found in all cases and at all sites of the disease. 2. The bacteria should be isolated from the infected person and maintained in pure culture. 3. The pure cultured microbe should cause symptoms of the disease on inoculation into a susceptible individual. 4. The bacteria should be reisolated from the intentionally infected host. The importance of microbiology： microbes in our body 1. Everyone has microorganisms in and on the body Some microorganisms live in humans and other animals and are needed to maintain the animals health. these make up the normal flora （正常菌群）; 2. Some Microorganisms cause disease. 3. The disease-producing properties of a species of microbe and the host's resistance are important factors in determining whether a person will contract a disease. 2.Microbes and Human Welfare 1. Microorganisms degrade dead plants and animals and recycle chemical elements to be used by living plants and animals. 2. Bacteria are used to decompose organic matter in sewage. Bioremediation processes use bacteria to clean up toxic wastes. 3. Bacteria that cause diseases in insects are being used as biological controls of insect pests. Biological controls are specific for the pest and do not harm the environment. 4. Using recombinant DNA, bacteria can produce important human proteins, such as insulin, beta-endorphin, and hepatitis B vaccine.Microorganisms can be used to help produce foods.They are also food sources (single-cell protein) themselves. 3.As a basic biological science：microorganisms are the best model systems for understanding basic life processes. All cells have much in common, what is true for E. coli is also true for elephant, only more so Simple yet representative Easiness and quickness to grow large quantity Common characterizes of microorganism•Big surface/volume •High absorption and transformation •Rapid growth and reproduction •Easiness to variation •high adaptation to environment •Diversity Review question
1.Match the following people to their contribution toward the advancement of microbiology.Ehrlich(a) First to observe bacteriaFleming(b) First to observe cells inHookeplant material and name_KochthemLister(c) Disproved spontaneousPasteurgenerationVan Leeuwenhoek(d)Proved that microorganisms can cause disease(e) Discovered penicillin(f) Used the first syntheticchemotheraputic agent First to employdisinfectants in surgical procedures2. Match the following microorganisms to their descriptions.Algae(a) Not composed of cellsBacteria(b) Cell wall made of chitinFungi(c) Cell wall made ofProtozoompeptidoglycanViruses(d) Cell wall made of cellulose, photosynthetic(e) Complex cell structure lacking a cell wall3.Briefly state the role played by microorganisms in each of the following(a)Biological control of pests(b)Recycling of elements(c)Normalflora(d)Sewagetreatment(e)Human insulin production4 The microbes were first formally observed in the mid-1600's, but the cell theory wasn'tenunciated until 1839.Write a brief essay explaining why microbiology did not become aformallyrecognized science until Pasteur's time.5.Compareandcontrasttheworksof Louis Pasteurand RobertKoch,intermsofbothapplied andbasic science.6.Microorganisms can bebothbeneficial and harmfultohumans.Although wetend toemphasizethe harmful microorganisms (infectious disease agents), many more are beneficial than harmful.In what ways are microorganisms important in thefood, agriculture,and industries?7.LouisPasteursworkon spontaneousgeneration ledtothedevelopmentofmethods forcontrolof the growthof microorganisms.Robert Kochdeveloped criteria forthe studyof infectiousmicroorganisms,and developed thefirstmethodsforthegrowth of pureculturesofmicroorganismsBeijerinck and Winogradsky studied bacteria in soil and water, and developed the enrichmentculture technique. In the twentieth century, basic and applied microbiology have worked hand inhand to yield a number of important practical advances and a revolution in molecular biology.oHowdid Pasteur'sfamous experimentdefeat thetheoryofspontaneousgeneration?HowcanKoch's postulates prove cause and effect in a disease?Whowas thefirstpersontouse solid culturemedia inmicrobiology?What advantages do solid media offerfor the cultureofmicroorganisms?What istheenrichmentculturetechnique and why was it auseful newmethod inmicrobiology?4
4 1.Match the following people to their contribution toward the advancement of microbiology. _ Ehrlich (a) First to observe bacteria _ Fleming (b) First to observe cells in _ Hooke plant material and name _ Koch them _ Lister (c) Disproved spontaneous _ Pasteur generation _ Van Leeuwenhoek (d) Proved that microorganisms can cause disease (e) Discovered penicillin (f) Used the first syntheticchemotheraputic agent First to employ disinfectants in surgical procedures 2. Match the following microorganisms to their descriptions. _ Algae (a) Not composed of cells _ Bacteria (b) Cell wall made of chitin _ Fungi (c) Cell wall made of _ Protozoom peptidoglycan _ Viruses (d) Cell wall made of cellulose; photosynthetic (e) Complex cell structure lacking a cell wall 3.Briefly state the role played by microorganisms in each of the following. (a) Biological control of pests (b) Recycling of elements (c) Normal flora (d) Sewage treatment (e) Human insulin production 4 The microbes were first formally observed in the mid-1600's, but the cell theory wasn't enunciated until 1839. Write a brief essay explaining why microbiology did not become a formally recognized science until Pasteur's time. 5. Compare and contrast the works of Louis Pasteur and Robert Koch, in terms of both applied and basic science. 6. Microorganisms can be both beneficial and harmful to humans. Although we tend to emphasize the harmful microorganisms (infectious disease agents), many more are beneficial than harmful. ●In what ways are microorganisms important in the food , agriculture,and industries? 7. Louis Pasteur´s work on spontaneous generation led to the development of methods for control of the growth of microorganisms. Robert Koch developed criteria for the study of infectious microorganisms, and developed the first methods for the growth of pure cultures of microorganisms. Beijerinck and Winogradsky studied bacteria in soil and water, and developed the enrichment culture technique. In the twentieth century, basic and applied microbiology have worked hand in hand to yield a number of important practical advances and a revolution in molecular biology. ●How did Pasteur´s famous experiment defeat the theory of spontaneous generation? ●How can Koch´s postulates prove cause and effect in a disease? ●Who was the first person to use solid culture media in microbiology? ●What advantages do solid media offer for the culture of microorganisms? ●What is the enrichment culture technique and why was it a useful new method in microbiology?
Chapter2prokayoticmicroorganism(原核微生物)第二章原核微生物prokaryotic cellsThe chief distinguishing characteristics of procaryotic cells aregenetic material (DNA) is not enclosed within a membrane.12.They lack other membrane bounded organelles.3Their DNA is not associated with histone proteins (special chromosomal proteinsfound in eucaryotes).Their cell walls almost always contain the complexpolysaccharidepeptidoglycan（肽聚糖）.Bacteria(细菌）andarchaeobacteria（古细菌）Bacteria are small, single-celled,microorganisms thatbelong to a group called prokaryotesBacteria are ubiquitous. They are a highly successful and diverse group of organisms that canobtain energy and carbon from a wide range of sources and therefore can colonize every niche onour planet from deep ocean trenches to volcanic craters. In the 1970s, using DNA sequencinginformation,itwasfoundthatthegroupweknow asthebacteriacould besplit into two,theeubacteriaand the archaeobacteria and it appears that these two groups evolved awayfrom each other very early in the history of living things at about the same time that the firstgroup of eukaryotic cells evolved. Members of the eubacteria include some of the morefamiliarbacteria such as Escherichia colt（大肠埃希氏菌）and Staphylococcusaureus（金黄色葡萄球菌）andarethe prokaryotesthat are best studiedandunderstoodThearchaebacteria are avery diverse group of organisms,which differ fromthe eubacteria （真细菌 o in a number offeatures having, in particular,very different cell walls and membranes.Thisgroup includes bacteria that arecapableofexistingin extremeenvironments。Size, Shape, and Arrangement of BacterialCellsMost bacteria are from 0.20 to 2.0 /μm in diameter and from 2 to 8μm in length.2The three basic bacterial shapes are coccus(spheres), bacillus(rods),and spiral (twisted).3.In addition to the three basic shapes, there are star-shaped cells (genus Stella) andrecentlydiscoveredsquare,flatcells(halophilic(盐的）archaeobacteria)andtriangularcells (Haloarcula)the shapeofabacterium isdetermined byheredity.However,anumberofenvironmental4conditions can alter that shape.Pleomorphic(多型性的）bacteria can assume severalshapes.Gram Stain:Theeubacteria arefrequently divided into two groups on the basis of their reaction to a stain devisedbyChristianCram in1884.Thedifferential reaction tothe stainingprocedureisbecauseof thestructure of the cell wall in these two groups of bacteria.Gram-positive bacteria have a single5
5 Chapter 2 prokayotic microorganism(原核微生物)第二章 原核微生物 prokaryotic cells The chief distinguishing characteristics of procaryotic cells are: 1. genetic material (DNA) is not enclosed within a membrane. 2. They lack other membrane bounded organelles. 3. Their DNA is not associated with histone proteins (special chromosomal proteins found in eucaryotes).Their cell walls almost always contain the complex polysaccharide peptidoglycan（肽聚糖）.Bacteria(细菌) and archaeobacteria （古细菌） Bacteria are small, single-celled, microorganisms that belong to a group called prokaryotes . Bacteria are ubiquitous. They are a highly successful and diverse group of organisms that can obtain energy and carbon from a wide range of sources and therefore can colonize every niche on our planet from deep ocean trenches to volcanic craters. In the 1970s, using DNA sequencing information, it was found that the group we know as the bacteria could be split into two, the eubacteria and the archaeobacteria and it appears that these two groups evolved away from each other very early in the history of living things at about the same time that the first group of eukaryotic cells evolved. Members of the eubacteria include some of the more familiar bacteria such as Escherichia colt（大肠埃希氏菌） and Staphylococcus aureus（金 黄色葡萄球菌） and are the prokaryotes that are best studied and understood. The archaebacteria are a very diverse group of organisms, which differ from the eubacteria（真 细菌 0 in a number of features having, in particular, very different cell walls and membranes. This group includes bacteria that are capable of existing in extreme environments。 Size, Shape, and Arrangement of Bacterial Cells 1 Most bacteria are from 0.20 to 2.0 /µm in diameter and from 2 to 8µm in length. 2 The three basic bacterial shapes are coccus(spheres), bacillus(rods),and spiral (twisted). 3 In addition to the three basic shapes, there are star-shaped cells (genus Stella) and recently discovered square, flat cells (halophilic(嗜盐的) archaeobacteria) and triangular cells (Haloarcula) 4 the shape of a bacterium is determined by heredity.However, a number of environmental conditions can alter that shape.Pleomorphic(多型性的) bacteria can assume several shapes. Gram Stain： The eubacteria are frequently divided into two groups on the basis of their reaction to a stain devised by Christian Cram in 1884. The differential reaction to the staining procedure is because of the structure of the cell wall in these two groups of bacteria. Gram-positive bacteria have a single
membrane called the cytoplasmic (orplasma)membrane,surroundedby a thick layer ofpeptidoglycan (20-80 nm). The Gram-negative bacteria have only a thin layer of peptidoglycan(1-3nm)but on the outside ofthis there is a further outermembrane which acts as an additionalbarrier.TheprocedurefortheGram stain isas follows.Fixed cells arestained withadark stain suchas crystal violet, followed by iodine which complexes with the stain in the cell wall of thebacteria. Alcohol is added, which washes the dark stain of crystal violet-iodine out of ceils thathave thin cell walls but notfromthose that havethick cell walls.Finally,a paler stain such ascarbol fuschin, called a counter stain, is added which stains the decolorized cells pink but is notseen on the dark staining cells that retained the first stain. The cells that retain the stain (with thickcell walls) are called Gram-positive and appear dark purple under light microscopy. The onesthat lose the stain (with thin cell walls and anouter membrane)arecalled Gram-negativeandstainpinkorpalepurpleThe Cell Wall1Thecell wall surrounds theplasma membraneandprotects the cell fromchanges inosmoticpressure（渗透压）and provides rigidity and strength.2The bacterial cell wall consists of peptidoglycan（肽聚糖），a polymer consisting of NAGand NAM and short chains of amino acids.3.Gram-positive（革兰氏阳性）cell walls consistofmanylayersof peptidoglycan and alsocontainteichoicacids（垣酸），x.Gram-negative（革兰氏阴性）bacteriahavealipidprotein-lipopolysaccharide-phospholipidouter membrane surrounding a thin peptidoglycan layer.5.Theoutermembrane protects the cellfrom phagocytosis and penicillin（青霉素），lysozyme（溶菌酶），and other chemicals.6.Porins（孔蛋白）areproteins thatpermit smallmolecules topass throughtheoutermembrane; specific channel proteins allow other molecules to move through the outermembrane.7.Thelipopolysaccharide（脂多糖，LPs）component ofthe outermembrane consists ofsugars that function as antigens and lipidA,which is an endotoxin（内毒素）teichoic acid:Gram-positive cell walls also contain large amounts of another polymer, called teichoic acid,made up of glycerol or ribitol joined by phosphate groups.D-Ala, glucose or sugars may beattached to the glycerol or ribitol and the polymers are attached either directly to the NAM in thepeptidoglycan or to lipids in the membrane (in this case they are called lipoteichoic acids). Thefunction of these molecules is unclear but they may have arole in maintaining the structure of the6
6 membrane called the cytoplasmic (or plasma) membrane, surrounded by a thick layer of peptidoglycan (20-80 nm). The Gram-negative bacteria have only a thin layer of peptidoglycan (1-3 nm) but on the outside of this there is a further outer membrane which acts as an additional barrier. The procedure for the Gram stain is as follows. Fixed cells are stained with a dark stain such as crystal violet, followed by iodine which complexes with the stain in the cell wall of the bacteria. Alcohol is added, which washes the dark stain of crystal violet-iodine out of ceils that have thin cell walls but not from those that have thick cell walls. Finally, a paler stain such as carbol fuschin, called a counter stain, is added which stains the decolorized cells pink but is not seen on the dark staining cells that retained the first stain. The cells that retain the stain (with thick cell walls) are called Gram-positive and appear dark purple under light microscopy. The ones that lose the stain (with thin cell walls and an outer membrane) are called Gram-negative and stain pink or pale purple The Cell Wall 1. The cell wall surrounds the plasma membrane and protects the cell from changes in osmotic pressure（渗透压）and provides rigidity and strength. 2. The bacterial cell wall consists of peptidoglycan（肽聚糖）, a polymer consisting of NAG and NAM and short chains of amino acids. 3. Gram-positive（革兰氏阳性） cell walls consist of many layers of peptidoglycan and also contain teichoic acids（垣酸）. 4. Gram-negative（革兰氏阴性）bacteria have a lipidprotein-lipopolysaccharide-phospholip id outer membrane surrounding a thin peptidoglycan layer. 5. The outer membrane protects the cell from phagocytosis and penicillin（青霉素）, lysozyme （溶菌酶）, and other chemicals. 6. Porins（孔蛋白）are proteins that permit small molecules to pass through the outer membrane; specific channel proteins allow other molecules to move through the outer membrane. 7. The lipopolysaccharide（脂多糖，LPS） component of the outer membrane consists of sugars that function as antigens and lipid A, which is an endotoxin（内毒素）. teichoic acid: Gram-positive cell walls also contain large amounts of another polymer, called teichoic acid, made up of glycerol or ribitol joined by phosphate groups. D-Ala, glucose or sugars may be attached to the glycerol or ribitol and the polymers are attached either directly to the NAM in the peptidoglycan or to lipids in the membrane (in this case they are called lipoteichoic acids). The function of these molecules is unclear but they may have a role in maintaining the structure of the
cell wall and in the control ofautolysis.periplasmicspace（周质空间）The outer membrane of Gram-negative bacteria acts as an additional barrier protecting thepeptidoglycan from toxic compounds such as lysozyme which act on the cell wall. It createsan aqueous space between the twomembranes called theperiplasmic space which is thoughtto have a gel-like structure with a loose network of peptidoglycan running through it.Estimates as to the width of thepeptidoglycan varyfrom1-71 nm but it has proved to bedifficultto obtain a real definitive value.The periplasmic space contains a range of proteinsassociated with:.transport ofnutrientsintothecell:.enzymes that are involved in nutrientacquisition such as proteases;:enzymes that defend the cell againsttoxic chemicals such as B-lactamases that destroypenicillin.outermembraneThe outer membrane of Gram-negative bacteria is made up of phospholipidsmembrane,but it also contains some unique featuresPoresformedbyproteins called porins such asOmpFandOmpCthatallowthepassivediffusionof smallmoleculesintotheperiplasmicspace2.An abundant small lipoprotein called Braun's lipoprotein thatiscovalentlybound tothepeptidoglycan andis embedded intheoutermembranebyit shydrophobic lipid,therefore holding the peptidoglycan and outer membraneclose together.LPS molecules are found in the outer leaflet of the outer membrane projecting into the3.surroundingmedium.Atypical（缺陷的）cellwalls1.Mycoplasma（支原体）is a bacterial genus that naturallylackscellwalls2.Archaeobacteriahavepseudomurein（假肽聚糖）；theylackpeptidoglycan3..Lforms aremutantbacteria withdefective cell walls.Archaeobacterial cell wallsOne of the distinctive features of archaebacteria is the nature of the lipids in the plasmamembrane which, unlike the ester-linked lipids of eubacteria and eukaryotes are ether-linked toglycerol. They are also long chained and branched. Archaebacterial cell walls and envelopesshowgreat diversityand complexity in structure.They do notcontain peptidoglycan although somedo have a similar compound called pseudomurein which contains N-acetyl-alosaminuronic acid inplace of muramic acid.Another common type of cell wall is the S-layer,a two-dimensional,paracrystalline, array of protein or glycoprotein on the cell surface. Others have thick7
7 cell wall and in the control of autolysis. periplasmic space（周质空间） The outer membrane of Gram-negative bacteria acts as an additional barrier protecting the peptidoglycan from toxic compounds such as lysozyme which act on the cell wall. It creates an aqueous space between the two membranes called the periplasmic space which is thought to have a gel-like structure with a loose network of peptidoglycan running through it. Estimates as to the width of the peptidoglycan vary from 1-71 nm but it has proved to be difficult to obtain a real definitive value. The periplasmic space contains a range of proteins associated with: • transport of nutrients into the cell; • enzymes that are involved in nutrient acquisition such as proteases; • enzymes that defend the cell against toxic chemicals such as в-lactamases that destroy penicillin. outer membrane The outer membrane of Gram-negative bacteria is made up of phospholipids membrane,but it also contains some unique features 1. Pores formed by proteins called porins such as OmpF and OmpC that allow the passive diffusion of small molecules into the periplasmi c space. 2. An abundant small lipoprotein called Braun's lipoprotein that is covalentlybound to the peptidoglycan and is embedded in the outer membrane by it s hydrophobic lipid, therefore holding the peptidoglycan and outer membraneclose together. 3. LPS molecules are found in the outer leaflet of the outer membrane projecting into the surrounding medium. Atypical（缺陷的） cell walls 1. Mycoplasma（支原体） is a bacterial genus that naturally lacks cell walls. 2. Archaeobacteria have pseudomurein（假肽聚糖）; they lack peptidoglycan. 3. .L forms are mutant bacteria with defective cell walls. Archaeobacterial cell walls One of the distinctive features of archaebacteria is the nature of the lipids in the plasma membrane which, unlike the ester-linked lipids of eubacteria and eukaryotes are ether-linked to glycerol. They are also long chained and branched. Archaebacterial cell walls and envelopes show great diversity and complexity in structure. They do not contain peptidoglycan although some do have a similar compound called pseudomurein which contains N-acetyl-alosaminuronic acid in place of muramic acid. Another common type of cell wall is the S-layer, a two-dimensional, paracrystalline, array of protein or glycoprotein on the cell surface. Others have thick
polysaccharidewallsoutsidetheirplasmamembraneDAMAGETOTHECELLWALLpeptidoglycan used to be a target for antimicrobial agents that destroy prokaryotic cellsspecifically, but do not harm eukaryotic cells, an example ofthis is the antibiotic penicillin(TopicF7).Lysozyme, a natural antibacterial agent found in tears and natural secretions, breaks down thelinkagebetweenNAM and NAG.Removal of the cell wall under conditions wherethe osmolarityof the medium is the same as the inside of the cell (isotonic solution) results in the formation ofroundprotoplasts（原生质体）（Gram-positives）orspheroplasts（球形体）（Gram-negatives）which survive as long as the isotonicity is maintained. These structures lyse, however, if placed ina dilute medium, illustrating the importance of peptidoglycan to the cells survival.1.In the presence of lysozyme, gram-positive cell walls are destroyed and the remainingcellular contents are referred to as a protoplast.2.In the presence of lysozyme, gram-negative cell walls are not completely destroyed andthe remaining cellular contents are referred to as a spheroplast.3.Protoplasts and spheroplasts are subject to osmotic lysis4.Antibiotics suchaspenicillin interferewithcell wall synthesisPLASMA (CYTOPLASMIC) MEMBRANEThe plasma membrane encloses the cytoplasm and is a phospholipid bilayer withprotein (fluid mosaic).2mostofbacterialackofsteriol（固醇）3The plasma membrane is selectively permeable.4Plasma membranes carry enzymes for metabolic reactions, such as nutrientbreakdown, energy production, and photosynthesis.5Mesosomes-irregularinfoldings oftheplasmamembrane-are nowconsideredartifacts6.PlasmamembranescanbedestroyedbyalcoholsandpolymyxinCYTOPLASM1Cytoplasmis thefluidcomponent insidetheplasmamembrane.2The cytoplasm is mostly water,with inorganicand organic molecules,DNA,ribosomes, and inclusions.RIBOSOMESThe cytoplasm of a procaryote contains numerous 70S ribosomes,ribosomes consist ofrRNA and protein.2Proteinsynthesis occursatribosomes,thiscanbeinhibited bycertainantibioticsINCLUSIONS8
8 polysaccharide walls outside their plasma membrane. DAMAGE TO THE CELL WALL peptidoglycan used to be a target for antimicrobial agents that destroy prokaryotic cells specifically, but do not harm eukaryotic cells; an example of this is the antibiotic penicillin (Topic F7). Lysozyme, a natural antibacterial agent found in tears and natural secretions, breaks down the linkage between NAM and NAG. Removal of the cell wall under conditions where the osmolarity of the medium is the same as the inside of the cell (isotonic solution) results in the formation of round protoplasts(原生质体) (Gram-positives) or spheroplasts(球形体) (Gram-negatives) which survive as long as the isotonicity is maintained. These structures lyse, however, if placed in a dilute medium, illustrating the importance of peptidoglycan to the cells' survival. 1. In the presence of lysozyme, gram-positive cell walls are destroyed and the remaining cellular contents are referred to as a protoplast. 2. In the presence of lysozyme, gram-negative cell walls are not completely destroyed and the remaining cellular contents are referred to as a spheroplast. 3. Protoplasts and spheroplasts are subject to osmotic lysis. 4. Antibiotics such as penicillin interfere with cell wall synthesis. PLASMA (CYTOPLASMIC) MEMBRANE 1 The plasma membrane encloses the cytoplasm and is a phospholipid bilayer with protein (fluid mosaic). 2 most of bacteria lack of steriol（固醇） 3 The plasma membrane is selectively permeable. 4 Plasma membranes carry enzymes for metabolic reactions, such as nutrient breakdown, energy production, and photosynthesis. 5 Mesosomes—irregular infoldings of the plasma membrane—are now considered artifacts 6 .Plasma membranes can be destroyed by alcohols and polymyxin. CYTOPLASM 1 Cytoplasm is the fluid component inside the plasma membrane. 2 The cytoplasm is mostly water, with inorganic and organic molecules, DNA, ribosomes, and inclusions. RIBOSOMES 1 The cytoplasm of a procaryote contains numerous 70S ribosomes; ribosomes consist of rRNA and protein. 2 Protein synthesis occurs at ribosomes; this can be inhibited by certain antibiotics. INCLUSIONS
Inclusions（内含物）arereservedepositsfoundinprocaryoticandeucaryoticcellsE2Amongtheinclusionsfoundinbacteriaaremetachromaticgranules（异染粒）（inorganicphosphate),polysaccharide granules(，多糖，usually glycogen orstarch),lipid inclusions（脂滴），sulfurgranules（硫粒），carboxysomes（，羧酶体，ribulose1,5-diphosphatecarboxylase)，andgasvacuoles（气泡）NUCLEARAREA1.The nuclear area contains the DNA of the bacterial chromosome.Bacteria can also containplasmids, which are extrachromosomal DNA circles.capsule or slime layercapsule（英膜）orslime（黏液层）layerisagelatinous polysaccharideand/orpolypeptidecovering.2.Capsulesmayprotectpathogensfromphagocytosis（吞噬）3.Capsules provideadherence to surfaces,prevent desiccation,andmayprovidenutrientsFLAGELLA1.Flagella（鞭毛）arerelativelylongfilamentousappendagesconsistingofafilamenthookand basal body.2Procaryoticflagellarotatetopushthecell.Motile（运动）3.bacteria exhibit taxis （趋性）positive taxis is movement toward an attractant andnegativetaxisismovementawayfromarepellent.FIMBRIAEANDPILIF1fimbriae（菌毛）and pili（性毛）are shortthin appendages2Fimbriae help cells adhere to surfaces3.Pili join cells for the transfer of DNA from one cell to anotherENDOSPORES（芽孢）Endospores are resting structures formed by some bacteria for survival during adverseenvironmental conditions.2.Theprocess of endosporeformation is called sporulation; the return ofan endosporeto itsvegetative state iscalled germinationEndospores are a method as survival, not one of reproduction. Certain bacteria will form a sporewithintheircellmembrane(an endospore)that allowsthemtowaitoutdeterioratingenvironmentalconditions.Certaindisease causingbacteria (such as the one that causes the disease Anthrax)canbevirulent(capableof causingan infection)1300yearsafterformingtheirendospore!)BACTERIALDIVISIONThenormal reproductive method of bacteria is binaryfission, in which a singlecell1.9
9 1 Inclusions（内含物） are reserve deposits found in procaryotic and eucaryotic cells. 2 Among the inclusions found in bacteria are metachromatic granules（异染粒） (inorganic phosphate), polysaccharide granules (，多糖，usually glycogen or starch), lipid inclusions （脂滴）,sulfur granules（硫粒）, carboxysomes (，羧酶体，ribulose 1,5-diphosphate carboxylase), and gas vacuoles（气泡）. NUCLEAR AREA 1. The nuclear area contains the DNA of the bacterial chromosome. Bacteria can also contain plasmids, which are extrachromosomal DNA circles. capsule or slime layer 1. capsule（荚膜） or slime（黏液层） layer is a gelatinous polysaccharide and/or polypeptide covering. 2. Capsules may protect pathogens from phagocytosis（吞噬）. 3. Capsules provide adherence to surfaces, prevent desiccation, and may provide nutrients. FLAGELLA 1. Flagella（鞭毛） are relatively long filamentous appendages consisting of a filament, hook, and basal body. 2. Procaryotic flagella rotate to push the cell.Motile（运动）. 3. bacteria exhibit taxis（趋性）—positive taxis is movement toward an attractant and negative taxis is movement away from a repellent. FIMBRIAE AND PILIF 1. fimbriae（菌毛） and pili（性毛） are short, thin appendages. 2. Fimbriae help cells adhere to surfaces. 3. Pili join cells for the transfer of DNA from one cell to another. ENDOSPORES（芽孢） 1. Endospores are resting structures formed by some bacteria for survival during adverse environmental conditions. 2. The process of endospore formation is called sporulation; the return of an endospore to its vegetative state iscalled germination. Endospores are a method as survival, not one of reproduction. Certain bacteria will form a spore within their cell membrane (an endospore) that allows them to wait out deteriorating environmental conditions. Certain disease causing bacteria (such as the one that causes the disease Anthrax) can be virulent (capable of causing an infection) 1300 years after forming their endospore!） BACTERIAL DIVISION 1. The normal reproductive method of bacteria is binary fission, in which a single cell
divides into two identical cells2Some bacteria reproduceby budding.,aerial sporeformation, orfragmentation.binary fission (二分裂)The method by which bacteria reproduce. The circular DNA molecule isreplicated; then the cell splits into two identical cells, each containing anexact copy of theoriginal cell's DNA.ActinomycesActinomycetes(放线菌）are filamentous, gram-positive bacilli that form a branchingmyceliumCyanobacteria（蓝细菌）：Blue-green bacteria;unicellular or filamentous chains of cells that carryout photosynthesis.Rickttsias,chlamydias and mycoplasmasThe ricktsias（立克次氏体）and chlamydias（衣原体）are gram-negative obligate intracellular parasitesthat key metabolic enzymes.The ricketsias are extremely small, pleomorphic rods or cocobacilli that cannot synthessiz their own ATPMost have acomplex life-style that cyces between arthropod vectors and vertebrate hostsThe rickettsias are ususlly transmitted by tickor tick fecesThe chlamydias are small, gram-negative, pleomorphic, intracellular parasites that have nocatabolic pathways.They exist in twoforms:the elementarybody,which is theformtransmittedbetween human hosts through direct contact and body secretions, and the reticulate body,whichmultiplies intracellularly.Chlamydiatrachomatis（沙眼衣原体）istheagentof severalSTDs:NGU（nongonococcalurethritis),pelvic inflammatory disease, and lymphogranuloma venereum.It also causes oculartrachoma, a serious eyeinfectionChlamydia pneumoniae(肺炎衣原体)is the agent of respiratory infections in young adults andasthmatics.Chlamydiapsittaci（鹦鹉热衣原体）istheagentofornithosis,aninfluenza-likediseasecarriedbybirds that has serious systemic complications ifuntreated.Antibiotic therapy is usually successful.Mycoplasmas（支原体）aretinypleomorphicbacteriathatlackacell wall.Althoughmost speciesareparasitic,mycoplasmas canbe cultured on complexartificial media.They areconsideredmembrane parasites because theybind tightlyto epithelial linings of the respiratoryand urogenitaltracts.Mycoplasma pneumoniae(肺炎支原体）istheagentof primaryatypical pneumonia（walkingpneumonia).10
10 divides into two identical cells. 2. Some bacteria reproduce by budding., aerial spore formation, or fragmentation. binary fission（二分裂） The method by which bacteria reproduce. The circular DNA molecule is replicated; then the cell splits into two identical cells, each containing an exact copy of the original cell's DNA. Actinomyces Actinomycetes(放线菌) are filamentous, gram-positive bacilli that form a branching mycelium. Cyanobacteria（蓝细菌）： Blue-green bacteria;unicellular or filamentous chains of cells that carry out photosynthesis. Rickttsias , chlamydias and mycoplasmas The rickttsias（立克次氏体） and chlamydias（衣原体） are gram-negative obligate intracellular parasites that key metabolic enzymes. The rickettsias are extremely small, pleomorphic rods or coccobacilli that cannot synthessiz their own ATP. Most have a complex life-style that cyces between arthropod vectors and vertebrate hosts. The rickettsias are ususlly transmitted by tickor tick feces. The chlamydias are small, gram-negative, pleomorphic, intracellular parasites that have no catabolic pathways. They exist in two forms: the elementary body, which is the form transmitted between human hosts through direct contact and body secretions, and the reticulate body, which multiplies intracellularly. Chlamydia trachomatis（沙眼衣原体） is the agent of several STDs: NGU (nongonococcal urethritis),pelvic inflammatory disease, and lymphogranuloma venereum. It also causes ocular trachoma, a serious eye infection. Chlamydia pneumoniae(肺炎衣原体) is the agent of respiratory infections in young adults and asthmatics. Chlamydia psittaci（鹦鹉热衣原体） is the agent of ornithosis, an influenza-like disease carried by birds that has serious systemic complications if untreated. Antibiotic therapy is usually successful. Mycoplasmas（支原体）are tiny pleomorphic bacteria that lack a cell wall. Although most species are parasitic, mycoplasmas can be cultured on complex artificial media. They are considered membrane parasites because they bind tightly to epithelial linings of the respiratory and urogenital tracts. Mycoplasma pneumoniae(肺炎支原体) is the agent of primary atypical pneumonia (walking pneumonia)