《环境工程微生物学》课程教学资源（英文教材）Foundations In Microbiology，8Th Edition（Kathleen Park Talaro）Mcgraw Hill 2012（彩色版）

6Chapter1 The Main Themes of MicrobiologyReproductive sporesntWDExSE74Bacteria:Mycobacteriumtuberculosis,aFungi:Thamnidium,a filamentousAlgae:desmids, Spirogyra filament,and diatomsrod-shaped cell(15,500x).fungus (400x)(golden cells) (500x),AsinglevirusparticleVirus:Herpessimplex,causeofcoldProtozoa:ApairofVorticella(500x),stalkedcellsHelminths:Cystsoftheparasiticroundwormsores (100,000x)Trichinella spiralis (250x)embedded in muscle.thatfeedbymeansofa whirlingrowofciliaFigure 1.3The six basic types of microorganisms.Organisms are not shown at theanificsoapproximatemagnification is providedoxygen.Today photosynthetic microorganisms (including algae)Microbial Involvement in Energyaccount for more than 50% of the earth's photosynthesis, contribut-and Nutrient Flowing the majority of the oxygen to the atmosphere (figure 1.5a).The microbes in all natural environments have lived and evolvedAnother process that helps keep the earth in balance isthere for billions of years.We do not yet know everything theythe process of biological decomposition and nutrient recycling.do, but it is likely they are vital components of the structure andDecomposition involves the breakdown of deadmatter andfunction of these ecosystems and critical to the operations of thewastes into simple compounds that can be directed back into theearthnatural cycles of living things (figure 1.5b). If it were not forMicrobes are deeply involved in the flow of energy and foodmultitudes of bacteria and fungi, many chemical elements wouldthrough the earth's ecosystems.'Most people are aware that plantsbecome lockedup and unavailableto organisms.In thelong-termcarry out photosynthesis, which is the light-fueled conversion ofschemeof things,microorganisms arethemainforces thatdrivecarbon dioxide to organic material,accompanied bytheformationthe structure and content of the soil, water, and atmosphere.of oxygen.But microorganisms werephotosynthesizing longbeforeFor example:the first plants appeared. In fact, they were responsible for changingEarth's temperature is regulated by"greenhouse gases,"suchthe atmosphere of the earth from one without oxygen to one withas carbon dioxide and methane, that create an insulation layerin the atmosphereand help retain heat.A significant proportionofthesegasesisproducedbymicrobeslivingintheenviron-ment and thedigestive tracts of animals1. Ecosysteiesoflivingo

6 Chapter 1 The Main Themes of Microbiology Algae: desmids, Spirogyra filament, and diatoms (golden cells) (500x). Helminths: Cysts of the parasitic roundworm, Trichinella spiralis (250x) embedded in muscle. Protozoa: A pair of Vorticella (500x), stalked cells that feed by means of a whirling row of cilia. Virus: Herpes simplex, cause of cold sores (100,000x). Fungi: Thamnidium, a filamentous fungus (400x) Bacteria: Mycobacterium tuberculosis, a rod-shaped cell (15,500x). A single vi A single virus particle rus particle Reproductive spores Figure 1.3 The six basic types of microorganisms. Organisms are not shown at the same magnifi cations so approximate magnifi cation is provided. Microbial Involvement in Energy and Nutrient Flow The microbes in all natural environments have lived and evolved there for billions of years. We do not yet know everything they do, but it is likely they are vital components of the structure and function of these ecosystems and critical to the operations of the earth. Microbes are deeply involved in the fl ow of energy and food through the earth’s ecosystems. 1 Most people are aware that plants carry out photosynthesis, which is the light-fueled conversion of carbon dioxide to organic material, accompanied by the formation of oxygen. But microorganisms were photosynthesizing long before the fi rst plants appeared. In fact, they were responsible for changing the atmosphere of the earth from one without oxygen to one with oxygen. Today photosynthetic microorganisms (including algae) account for more than 50% of the earth’s photosynthesis, contribut￾ing the majority of the oxygen to the atmosphere (fi gure 1.5a). Another process that helps keep the earth in balance is the process of biological decomposition and nutrient recycling. Decomposition involves the breakdown of dead matter and wastes into simple compounds that can be directed back into the natural cycles of living things (fi gure 1.5b). If it were not for multitudes of bacteria and fungi, many chemical elements would become locked up and unavailable to organisms. In the long-term scheme of things, microorganisms are the main forces that drive the structure and content of the soil, water, and atmosphere. For example: • Earth’s temperature is regulated by “greenhouse gases,” such as carbon dioxide and methane, that create an insulation layer in the atmosphere and help retain heat. A signifi cant proportion of these gases is produced by microbes living in the environ- 1. Ecosystems are communities of living organisms and their surrounding environment. ment and the digestive tracts of animals. taL75292_ch01_001-026.indd Page 6 11/3/10 5:49 PM user-f468 /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefiles /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefile

71.2General CharacteristicsofMicroorganismsandTheirRoles intheEarth's Environments1mmRangeofReproductivestructurehumanLouseMacroscopicofbreadmoldeyeMicroscopic100μmNucleusColonial alga(Pediastrum)AmoebaRangeoflightmicroscopeRedbloodcellWhitebloodcell10μmMostbacteriafallbetween1to10μmOinsize00Rod-shaped bacteriaCoccus-shapedbacteriaTumRickettsia bacteria(Escherichia coll)(Staphylococcus)200nmMycoplasmabacteriaPoxvirusAIDSvirus100nmHepatitis B virusRangePoliovirus10nmofelectronFlagellummicroscopeLargeproteinDiameterof DNA1nmRequireAmino acidspecial(small molecule)microscopes0.1nmHydrogen atom(1Angstrom)am)m22cm)m(dm)MetricScale(km)A(pte.m)setetromicrollinymi2A512mi000000001,000100100001.321210-1-2-36-8-9-10-11Log1o of meters-5-7Figure1.4Thesizeofthings.Commonmeasurements encounteredinmicrobiologyandascaleofcomparisonfromthemacroscopicto themicroscopic,molecular,and atomic.Most microbes encountered in ourstudies willfall between 1o0μm and 10 nm in overall dimensions.Themicrobesshownaremoreorlesstoscalewithinsizezonebutnotbetweensizezones.●Recent estimates propose that, based on weight and numbersBacteria and fungi live in complex associations with plants.up to 50% of all organisms exist within and beneath the earth'sThey assist the plants in obtaining nutrients and water and maycrust in soil, rocks, and even the frozen Antarctic (figure 1.5c)protect them against disease.Microbes form similar interrela-It is increasingly evident that this enormous underground com-tionshipswithanimals,notablyas residents ofnumerousmunity of microbes is a major force in weathering.mineralbodily sites.extraction,and soilformation

1.2 General Characteristics of Microorganisms and Their Roles in the Earth’s Environments 7 Figure 1.4 The size of things. Common measurements encountered in microbiology and a scale of comparison from the macroscopic to the microscopic, molecular, and atomic. Most microbes encountered in our studies will fall between 100 μm and 10 nm in overall dimensions. The microbes shown are more or less to scale within size zone but not between size zones. (1 Angstrom) Range of human eye Range of light microscope Range of electron microscope Require special microscopes 1 nm 10 nm 200 nm 10 µm 100 µm 1 mm Amino acid (small molecule) Hydrogen atom Diameter of DNA Large protein Flagellum Poliovirus AIDS virus Mycoplasma bacteria Rickettsia bacteria Rod-shaped bacteria (Escherichia coli) Red blood cell Most bacteria fall between 1 to 10 µm in size Amoeba Reproductive structure of bread mold White blood cell Coccus-shaped bacteria (Staphylococcus) Poxvirus 0.1 nm 1 µm Louse Macroscopic Microscopic Colonial alga (Pediastrum) 100 nm Hepatitis B virus Metric Scale Log10 of meters 3 2 1 0 –1 –2 –3 –4 –5 –6 –7 –8 –9 –10 –11 –12 1,000 100 10 1. 0 0 0, 0 0 0, 0 0 0, 0 0 0 kilometer (km) hektometer (hm) dekameter (dam) meter (m) decimeter (dm) centimeter (cm) millimeter (mm) micrometer ( Angstrom (Å) µm) nanometer (nm) picometer (pm) Nucleus • Recent estimates propose that, based on weight and numbers, up to 50% of all organisms exist within and beneath the earth’s crust in soil, rocks, and even the frozen Antarctic (fi gure 1.5c). It is increasingly evident that this enormous underground com￾munity of microbes is a major force in weathering, mineral extraction, and soil formation. • Bacteria and fungi live in complex associations with plants. They assist the plants in obtaining nutrients and water and may protect them against disease. Microbes form similar interrela￾tionships with animals, notably as residents of numerous bodily sites. taL75292_ch01_001-026.indd Page 7 11/3/10 5:49 PM user-f468 /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefiles /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefile

8Chapter1 The Main Themes of MicrobiologyCheckTAssessSections 1.1-1.2VMicroorganisms are defined as"living organisms too small tobeseen withthe nakedeye.Amongthemembers of this hugegroupoforganismsarebacteria.fungiprotozoa,algae,viruses,andparasiticworms.V Microorganisms live nearly everywhere and influence many bio-logical and physical activities on earth.VThe scope of microbiology is incredibly diverse.It includes basicmicrobialresearch,researchoninfectiousdiseases,studyofprevention and treatment of disease:environmental functions ofmicroorganisms, and industrial use of microorganisms for com-mercial, agricultural, and medical purposes.V Two basic cell lines appeared during evolutionary history:pro-(a)karyotes,whichare small and lackanucleusandorganelles,andeukaryotes, which are larger and have both a nucleus andorganelles.V Viruses are not cellular and are sometimes called particles ratherthan organisms.They are included in microbiology because oftheir small size,their close relationship with cells. and their in-volvementinnumerousinfectiousdiseases.Mostmicroorganismsaremeasuredinmicrometers,withtwoexceptions. The helminths are measured in millimeters, and thevirusesaremeasuredinnanometers.V Microorganisms are essential to the operation of the earth's ecosystems, as photosynthesizers, decomposers, and recyclers.IExplain theimportant contributions microorganisms make in theearth secosvstems2.Describe five different ways in whichhumans exploit microorgan-ismsforourbenefit.b3Identify the groups ofmicroorganisms included in the scope ofmicrobiology,andexplain the criteriafor including these groups inthefield4.Observefigure I.4and place themicrobespictured ina size rank-ing.goingfrom smallestto largest.Usethemagnification as yourgauge.5,Construct a table that displays all microbial groups based on whatkind of cells they have or do not have.6.Where do you suppose viruses came from?Whymust they existinside host cells?7:Explain this statement:Microorganisms-weneedto livewiththembecausewecan't livewithoutthem.1.3 Human UseofMicroorganisms(c)Figure1.5Amicroscopicwonderland.(a)AsummerpondxpectedLearningOutcomeis heavily laden with surface scum that reveals golden-coloreddiatoms and blue green bacteria in strands (600x magnification)6. Discuss the ways microorganisms may be applied to solve(b)A rotting tomato being decomposed bya furryforestof moldhumanproblems.includingRhizopus,bearingtinysacs ofsporesonastalk (250x)(c)EvenadrylakeinAntarctica,oneofthecoldestplacesonearth(-35C),canharbormicrobesunderitsicysheet.HereweseearedThe incredible diversityand versatility seen in microbes makethemcyanobacterium,Nostoc(3,000x),thathasprobablybeenfrozeninexcellent candidates for solving human problems. By accident orsuspendedanimationtherefor3,o00years.Thisisonekindofhabitatchoice, humanshavebeen using microorganismsfor thousands ofonearththatmaywell beamodelforconditionsonMars

8 Chapter 1 The Main Themes of Microbiology Figure 1.5 A microscopic wonderland. (a) A summer pond is heavily laden with surface scum that reveals golden-colored diatoms and blue green bacteria in strands (6003 magnifi cation). (b) A rotting tomato being decomposed by a furry forest of mold including Rhizopus, bearing tiny sacs of spores on a stalk (2503). (c) Even a dry lake in Antarctica, one of the coldest places on earth (235°C), can harbor microbes under its icy sheet. Here we see a red cyanobacterium, Nostoc (3,0003), that has probably been frozen in suspended animation there for 3,000 years. This is one kind of habitat on earth that may well be a model for conditions on Mars. (a) (c) (b) Check&Assess Sections 1.1–1.2 ✔ Microorganisms are defi ned as “living organisms too small to be seen with the naked eye.” Among the members of this huge group of organisms are bacteria, fungi, protozoa, algae, viruses, and para￾sitic worms. ✔ Microorganisms live nearly everywhere and infl uence many bio￾logical and physical activities on earth. ✔ The scope of microbiology is incredibly diverse. It includes basic microbial research, research on infectious diseases, study of pre￾vention and treatment of disease, environmental functions of microorganisms, and industrial use of microorganisms for com￾mercial, agricultural, and medical purposes. ✔ Two basic cell lines appeared during evolutionary history: pro￾karyotes, which are small and lack a nucleus and organelles, and eukaryotes, which are larger and have both a nucleus and organelles. ✔ Viruses are not cellular and are sometimes called particles rather than organisms. They are included in microbiology because of their small size, their close relationship with cells, and their in￾volvement in numerous infectious diseases. ✔ Most microorganisms are measured in micrometers, with two exceptions. The helminths are measured in millimeters, and the viruses are measured in nanometers. ✔ Microorganisms are essential to the operation of the earth’s eco￾systems, as photosynthesizers, decomposers, and recyclers. 1. Explain the important contributions microorganisms make in the earth’s ecosystems. 2. Describe fi ve different ways in which humans exploit microorgan￾isms for our benefi t. 3. Identify the groups of microorganisms included in the scope of microbiology, and explain the criteria for including these groups in the fi eld. 4. Observe fi gure 1.4 and place the microbes pictured in a size rank￾ing, going from smallest to largest. Use the magnifi cation as your gauge. 5. Construct a table that displays all microbial groups based on what kind of cells they have or do not have. 6. Where do you suppose viruses came from? Why must they exist inside host cells? 7. Explain this statement: Microorganisms—we need to live with them because we can’t live without them. 1.3 Human Use of Microorganisms Expected Learning Outcome 6. Discuss the ways microorganisms may be applied to solve human problems. The incredible diversity and versatility seen in microbes make them excellent candidates for solving human problems. By accident or choice, humans have been using microorganisms for thousands of taL75292_ch01_001-026.indd Page 8 11/3/10 5:49 PM user-f468 /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefiles /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefile

91.3Human Use of Microorganismsyears to improve life and even to further human progress. Yeasts,aOne powerful technique for designing new organisms is termedtypeofmicroscopicfungi,causebreadtoriseandfermentsugartorecombinant DNA.This technology makes it possibletodeliber-make alcoholic beverages.Historical records show that householdsatelyalterDNAandto switchgenetic material fromone organismin ancient Egypt kept moldy loaves of bread to apply directly toto another. Bacteria and fungi were some of the first organisms tobe genetically engineered, because their relatively simple geneticwoundsandlesions,whichwasprobablythefirstuseofpenicillin!When humans manipulatemicroorganisms to makeproducts in anmaterial is readily manipulated in the laboratory.Recombinantindustrial settingitis called biotechnology.OnenewerapplicationDNA technology has unlimited potential in terms of medical, in-farms algae to extracta form of oil (biodiesel)to be used in place ofdustrial, and agricultural uses. Microbes can be engineered to syn-petroleumproducts (figure 1.6a).thesize desirable proteins such as drugs, hormones, and enzymesGenetic engineering is a newer area of biotechnology that ma-(see table 1.lc).nipulates thegenetics of microbes,plants,and animals for the pur-Among the genetically unique organisms that have been de-signed by bioengineers are bacteria that contain a natural pesticide,pose of creating new products and genetically modified organisms.yeasts that produce human hormones, pigs that produce hemoglo-bin, and plants that are resistant to disease (see table 1.ld).Thetechniques have also paved the way for characterizing humangenetic material and diseases.Another way of tapping into the unlimited potential of micro-organisms is the relatively new science of bioremediation.*Thisprocess introduces microbes into theenvironmentto restore stabil-ityortocleanuptoxicpollutants.Bioremediationisrequiredtocontrol themassive levels of pollution that result from humanactivities.Microbes have a surprising capacity to break downchemicals that would be harmful to other organisms.Agencies andcompanies have developed microbes to handle oil spills and de-toxify sites contaminated with heavy metals,pesticides, and evenradioactive wastes (figure 1.6b).The solid waste disposal industryis focusing on methods for degrading the tons of garbage in land-fills, especially plastics and paper products. Oneform of bioreme-(a)diationthathasbeeninuseforsometimeisthetreatmentofwaterand sewage.With dwindling cleanfreshwater supplies worldwide,itwillbecomeevenmoreimportanttofind waystoreclaimpol-luted water.CONTINUINGCASE FILEThegenetic technologyfeatured inthis case is currentlyfocusedon mapping the microbial diversity of habitats such as soil,icebergs,hot springs,deep-ocean sediments,andthe humanbody.This will allowus tomaximizeourunderstandingof thesecomplexcommunitiesandtocomprehendhowtheyareinvolved in the functions of the earth and all of its lifeforms.Whatwillikelybetheresultofprobingallof thehabitatsonearthwiththistypeoftechnology?(b)Otherthan discovering andattemptingto identifyhiddenFigure 1.6Microbesatwork.(a)Algaespecialistspeerfromcommunitiesofmicrobes,whatcouldbesomeothertheir biodiesel bioreactor, a platform of hanging bags containingpossible rationales for modern-day microbe hunting?culturesofsingle-celledalgae(seeinset750x).TheirresearchwilltestthecapacityofalqaetomassproduceoilthatcouldbeusedasFora wrap-up,seethe Case FilePerspectiveonpage23.analternativetofossilfuels.Sofar,thisalternatewayofqrowingrenewable fuels looks very promising and may truly provide agreensourceof energy.(b)Workers removewaste from theHanfordNuclear Facility in Washington state that has been dangerouslycontaminated with spentradioactive substances.The cleanup of thissite is expected to take several years.A newly discovered bacterium,2. DNA, or deoxyribonucleic acid, the chemical substance that comprises the geneticShewanella (inset 5,o00x),is being tested as a bioremediationmaterial of organisms.measure. It is capable of reducing and detoxifying even dangerous+bioremediation (by'-oh-ree-mee-dee-ay'-shun) bios, life; re, again; mederi, toelementssuchasuranium.heal. The usc of biological agents to remedy environmental problems

1.3 Human Use of Microorganisms 9 2. DNA, or deoxyribonucleic acid, the chemical substance that comprises the genetic material of organisms. * bioremediation (by9-oh-ree-mee-dee-ay0-shun) bios, life; re , again; mederi, to heal. The use of biological agents to remedy environmental problems. Figure 1.6 Microbes at work. (a) Algae specialists peer from their biodiesel bioreactor, a platform of hanging bags containing cultures of single-celled algae (see inset 7503). Their research will test the capacity of algae to mass produce oil that could be used as an alternative to fossil fuels. So far, this alternate way of growing renewable fuels looks very promising and may truly provide a “green” source of energy. (b) Workers remove waste from the Hanford Nuclear Facility in Washington state that has been dangerously contaminated with spent radioactive substances. The cleanup of this site is expected to take several years. A newly discovered bacterium, Shewanella (inset 5,0003), is being tested as a bioremediation measure. It is capable of reducing and detoxifying even dangerous elements such as uranium. (a) (b) One powerful technique for designing new organisms is termed recombinant DNA. This technology makes it possible to deliber￾ately alter DNA 2 and to switch genetic material from one organism to another. Bacteria and fungi were some of the fi rst organisms to be genetically engineered, because their relatively simple genetic material is readily manipulated in the laboratory. Recombinant DNA technology has unlimited potential in terms of medical, in￾dustrial, and agricultural uses. Microbes can be engineered to syn￾thesize desirable proteins such as drugs, hormones, and enzymes (see table 1.1 c ). Among the genetically unique organisms that have been de￾signed by bioengineers are bacteria that contain a natural pesticide, yeasts that produce human hormones, pigs that produce hemoglo￾bin, and plants that are resistant to disease (see table 1.1 d ). The techniques have also paved the way for characterizing human genetic material and diseases. Another way of tapping into the unlimited potential of micro￾organisms is the relatively new science of bioremediation. * This process introduces microbes into the environment to restore stabil￾ity or to clean up toxic pollutants. Bioremediation is required to control the massive levels of pollution that result from human activities. Microbes have a surprising capacity to break down chemicals that would be harmful to other organisms. Agencies and companies have developed microbes to handle oil spills and de￾toxify sites contaminated with heavy metals, pesticides, and even radioactive wastes (fi gure 1.6b). The solid waste disposal industry is focusing on methods for degrading the tons of garbage in land￾fi lls, especially plastics and paper products. One form of bioreme￾diation that has been in use for some time is the treatment of water and sewage. With dwindling clean freshwater supplies worldwide, it will become even more important to fi nd ways to reclaim pol￾luted water. years to improve life and even to further human progress. Yeasts, a type of microscopic fungi, cause bread to rise and ferment sugar to make alcoholic beverages. Historical records show that households in ancient Egypt kept moldy loaves of bread to apply directly to wounds and lesions, which was probably the fi rst use of penicillin! When humans manipulate microorganisms to make products in an industrial setting, it is called biotechnology. One newer application farms algae to extract a form of oil (biodiesel) to be used in place of petroleum products (fi gure 1.6a). Genetic engineering is a newer area of biotechnology that ma￾nipulates the genetics of microbes, plants, and animals for the pur￾pose of creating new products and genetically modifi ed organisms. CONTINUING CASE FILE 1 The genetic technology featured in this case is currently focused on mapping the microbial diversity of habitats such as soil, icebergs, hot springs, deep-ocean sediments, and the human body. This will allow us to maximize our understanding of these complex communities and to comprehend how they are involved in the functions of the earth and all of its life forms. ■ What will likely be the result of probing all of the habitats on earth with this type of technology? ■ Other than discovering and attempting to identify hidden communities of microbes, what could be some other possible rationales for modern-day microbe hunting? For a wrap-up, see the Case File Perspective on page 23. taL75292_ch01_001-026.indd Page 9 11/3/10 5:50 PM user-f468 /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefiles /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefile

10Chapter1 TheMainThemes of Microbiology1.4MicrobialRolesinInfectiousTetanus 2.5%Parasitic diseases 2.5%DiseasesMiscellaneous 1.5%xpected Learning OutcomesRespiratory intitisxey7. Review the roles of microorganisms as parasites and(opathogens that cause infection and disease.eumonia infuenza8. Define what is meant by emerging and reemerging diseases.5%26%7%It is important to remind you that the large majority of microorgan-eeeisms are relatively harmless and highly beneficial and essential9%They live a free existence in the array of habitats on earth and areableto derive their requirements for life from thenonliving envi-ronment.Muchofthe.time.theyformcohesivecommunitieswith11%18%Tubeother organisms, sharing habitat and nutrients.Examples includethe natural partnerships that arefound in symbiosis and biofilmsrC17.5%Some microbes have adapted to a non-free-living lifestyleAIDScalled parasitism. A parasite lives in or on the body of a larger or-ganism called the host and derives most of its requirements fromDameadecueaethat host. A parasite's actions can damage the host through infec-dysentery,typhoid)tion and disease. Another term that can be used to specify this typeof microbe is pathogen.*Humanity is plagued by nearly 2.000 different microbes thatFigure1.7Worldwideinfectious diseasestatistics.Thiscan cause various types of disease.Infectious diseases still devas-figuredepicts the10 mostcommon infectious causes of death.tate human populations worldwide,despite significant strides inunderstanding and treating them.much of humanity,and they still kill a significant percentage ofThe most recent estimates from the World Health Organiza-the US population.Table 1.2 depicts the 10 top causes of deathtion (WHO)point to around 10 billion infections of all typesperyear (by all causes, infectious and noninfectious)in the Unitedacross the world every year.There are more infections than peo-StatesandworldwideTheworldwidedeathtoll from infectionsisple because many people acquire more than one infection. Infec-about 12 million people per year. In figure 1.7, you can see thetious diseases are also among the most common causes of death intop infectious causes of death displayed in a different way.Notethat many of these infections are treatablewith drugs or prevent-3. A biofilm is a complex network of microbes and their secretions that form in mostable with vaccines.natural environments, discussed further in chapter 4.Those hardest hit are residents in countries where access to ad-* pathogen (path'-oh-jen) Gr. pathos, disease, and gennan, to produce. Disease-equate medical care is lacking. One-third of the earth's inhabitantscausing agents.TABLE1.2TopCauses ofDeath-AllDiseasesUnited StatesNo.of DeathsWorldwideNo.of Deaths1. Heart disease696,9501. Heart disease8.12million557,2702.Cancer2.Stroke5.51million3.Stroke162.6703. Respiratory infection3.88million4. Chronic lower respiratory disease124,8004.Cancer3.33million5.Unintentional injury (accidents)106.7405. HIVIAIDS2.78million73,2506.Diabetes6. Chronic lower respiratory disease2.75million7.Infuenza and pneumonia*65,6801.80 million7.Diarrheal disease58,8708. Alzheimer disease8. Tuberculosis1.57million40,9709.Malaria1.27 million9. Kidney problems33,86510.Septicemia (bloodstream infection)10.Accidents1.19million*Diseases in red are those most clearly caused by microims,although cancer and other diseases may be associated with infections

10 Chapter 1 The Main Themes of Microbiology 3. A biofi lm is a complex network of microbes and their secretions that form in most natural environments, discussed further in chapter 4. * pathogen (path9-oh-jen) Gr. pathos, disease, and gennan, to produce. Disease￾causing agents. much of humanity, and they still kill a signifi cant percentage of the US population. Table 1.2 depicts the 10 top causes of death per year (by all causes, infectious and noninfectious) in the United States and worldwide. The worldwide death toll from infections is about 12 million people per year. In fi gure 1.7, you can see the top infectious causes of death displayed in a different way. Note that many of these infections are treatable with drugs or prevent￾able with vaccines. Those hardest hit are residents in countries where access to ad￾equate medical care is lacking. One-third of the earth’s inhabitants TABLE 1.2 Top Causes of Death—All Diseases United States No. of Deaths Worldwide No. of Deaths 1. Heart disease 696,950 1. Heart disease 8.12 million 2. Cancer 557,270 2. Stroke 5.51 million 3. Stroke 162,670 3. Respiratory infection 3.88 million 4. Chronic lower respiratory disease 124,800 4. Cancer 3.33 million 5. Unintentional injury (accidents) 106,740 5. HIV/AIDS 2.78 million 6. Diabetes 73,250 6. Chronic lower respiratory disease 2.75 million 7. Infl uenza and pneumonia * 65,680 7. Diarrheal disease 1.80 million 8. Alzheimer disease 58,870 8. Tuberculosis 1.57 million 9. Kidney problems 40,970 9. Malaria 1.27 million 10. Septicemia (bloodstream infection) 33,865 10. Accidents 1.19 million *Diseases in red are those most clearly caused by microorganisms, although cancer and other diseases may be associated with infections. 1.4 Microbial Roles in Infectious Diseases Expected Learning Outcomes 7. Review the roles of microorganisms as parasites and pathogens that cause infection and disease. 8. Defi ne what is meant by emerging and reemerging diseases. It is important to remind you that the large majority of microorgan￾isms are relatively harmless and highly benefi cial and essential. They live a free existence in the array of habitats on earth and are able to derive their requirements for life from the nonliving envi￾ronment. Much of the time, they form cohesive communities with other organisms, sharing habitat and nutrients. Examples include the natural partnerships that are found in symbiosis and biofi lms 3 . Some microbes have adapted to a non-free-living lifestyle called parasitism. A parasite lives in or on the body of a larger or￾ganism called the host and derives most of its requirements from that host. A parasite’s actions can damage the host through infec￾tion and disease. Another term that can be used to specify this type of microbe is pathogen.* Humanity is plagued by nearly 2,000 different microbes that can cause various types of disease. Infectious diseases still devas￾tate human populations worldwide, despite signifi cant strides in understanding and treating them. The most recent estimates from the World Health Organiza￾tion (WHO) point to around 10 billion infections of all types across the world every year. There are more infections than peo￾ple because many people acquire more than one infection. Infec￾tious diseases are also among the most common causes of death in Malaria Measles B Respiratory infections (pneumonia, influenza) Hepatitis Tuberculosis Diarrheal diseases (cholera, AIDS dysentery, typhoid) 26% 18% 17.5% 11% 9% 7% 5% Miscellaneous 1.5% Parasitic diseases 2.5% Tetanus 2.5% Figure 1.7 Worldwide infectious disease statistics. This fi gure depicts the 10 most common infectious causes of death. taL75292_ch01_001-026.indd Page 10 11/3/10 5:50 PM user-f468 /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefiles /Volume/201/MHDQ245/taL75292_disk1of1/0073375292/taL75292_pagefile