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Microbiology: A Microbiology: A Systems Approach, 2Systems Approach, 2ndnd
ed.ed.Chapter 5: Eukaryotic Cells and Chapter 5: Eukaryotic Cells and
MicroorganismsMicroorganisms
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5.1 The History of Eukaryotes5.1 The History of Eukaryotes First eukaryotic cells on earth approximately 2 First eukaryotic cells on earth approximately 2
billion years agobillion years ago Evidence points to these eukaryotic cells evolving Evidence points to these eukaryotic cells evolving
from prokaryotic organisms through intracellular from prokaryotic organisms through intracellular symbiosissymbiosis Eukaryotic Eukaryotic organellesorganelles originated from prokaryotic originated from prokaryotic
cells trapped inside of themcells trapped inside of them First primitive eukaryotes- probably single-celled and First primitive eukaryotes- probably single-celled and
independentindependent Eventually formed coloniesEventually formed colonies Cells within colonies became specializedCells within colonies became specialized Evolved in to multicellular organismsEvolved in to multicellular organisms
Eukaryotes have many levels of cellular Eukaryotes have many levels of cellular complexitycomplexity
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5.2 Form and Function of the 5.2 Form and Function of the Eukaryotic Cell: External StructuresEukaryotic Cell: External Structures
Figure 5.2
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Locomotor Appendages: Cilia and Locomotor Appendages: Cilia and FlagellaFlagella
Eukaryotic flagella are much different from Eukaryotic flagella are much different from those of prokaryotesthose of prokaryotes 10X thicker10X thicker Structurally more complexStructurally more complex Covered by an extension of the cell Covered by an extension of the cell
membranemembrane A single flagellum contains regularly A single flagellum contains regularly
spaced microtubules along its lengthspaced microtubules along its length 9 pairs surrounding a single pair9 pairs surrounding a single pair The 9 + 2 arrangementThe 9 + 2 arrangement
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Figure 5.3
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Cilia- similar to flagella but some Cilia- similar to flagella but some differencesdifferences ShorterShorter More numerousMore numerous Can also function as feeding and filtering Can also function as feeding and filtering
structuresstructures
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The GlycocalyxThe Glycocalyx Most eukaryotic cells have this outermost Most eukaryotic cells have this outermost
boundary that comes into direct contact with the boundary that comes into direct contact with the environmentenvironment
Usually composed of polysaccharides Usually composed of polysaccharides Appears as a network of fibers, a slime layer, or a Appears as a network of fibers, a slime layer, or a
capsulecapsule FunctionsFunctions
ProtectionProtection AdhesionAdhesion Reception of signalsReception of signals
The layer beneath the glycocalyx varies among The layer beneath the glycocalyx varies among eukaryoteseukaryotes Fungi and most algae have a thick, rigid cell wallFungi and most algae have a thick, rigid cell wall Protozoa and animal cells do not have this cell wallProtozoa and animal cells do not have this cell wall
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Form and Function of the Eukaryotic Form and Function of the Eukaryotic Cell: Boundary StructuresCell: Boundary Structures
Cell WallCell Wall RigidRigid Provide support and shapeProvide support and shape Different chemically from prokaryotic cell wallsDifferent chemically from prokaryotic cell walls FungiFungi
• Thick, inner layer of chitin or celluloseThick, inner layer of chitin or cellulose• Thin outer layer of mixed glycansThin outer layer of mixed glycans
AlgaeAlgae• Varied in chemical compositionVaried in chemical composition• May contain cellulose, pectin, mannans, and May contain cellulose, pectin, mannans, and
mineralsminerals
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Figure 5.5
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Cytoplasmic MembraneCytoplasmic Membrane Bilayer of phospholipids with protein Bilayer of phospholipids with protein
molecules embeddedmolecules embedded Also contain sterolsAlso contain sterols
• Gives stabilityGives stability• Especially important in cells without a cell wallEspecially important in cells without a cell wall
Selectively permeableSelectively permeable
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5.3 Form and Function of the 5.3 Form and Function of the Eukaryotic Cell: Internal StructuresEukaryotic Cell: Internal Structures
The Nucleus: The Control CenterThe Nucleus: The Control Center Separated from the cytoplasm by a nuclear Separated from the cytoplasm by a nuclear
envelopeenvelope• Two parallel membranes separated by a narrow spaceTwo parallel membranes separated by a narrow space• Perforated with nuclear poresPerforated with nuclear pores
Filled with nucleoplasmFilled with nucleoplasm Contains the Contains the nucleolusnucleolus
• rRNA synthesisrRNA synthesis• Colelction area for ribosomal subunitsColelction area for ribosomal subunits
ChromatinChromatin• Comprises the Comprises the chromosomeschromosomes
Long, linear DNA moleculesLong, linear DNA molecules Bound to Bound to histonehistone proteins proteins Visible during Visible during mitosismitosis
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Figure 5.6
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Figure 5.7
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Endoplasmic Reticulum (ER)Endoplasmic Reticulum (ER): A : A Passageway in the CellPassageway in the Cell
Microscopic series of tunnelsMicroscopic series of tunnels Used in transport and storageUsed in transport and storage Two kindsTwo kinds
Rough endoplasmic reticulum (RER)Rough endoplasmic reticulum (RER)• Originates from the outer membrane of the nuclear Originates from the outer membrane of the nuclear
envelopeenvelope• Extends through the cytoplasmExtends through the cytoplasm• Spaces in the RER- cisternae- transport materials from Spaces in the RER- cisternae- transport materials from
the nucleus to the cytoplasmthe nucleus to the cytoplasm• ““Rough” because of ribosomes attached to its surfaceRough” because of ribosomes attached to its surface• Proteins synthesized on the ribosomes shunted into the Proteins synthesized on the ribosomes shunted into the
cavity of the RER and held for later packaging and cavity of the RER and held for later packaging and transporttransport
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Figure 5.8
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Smooth endoplasmic reticulum (SER)Smooth endoplasmic reticulum (SER) Closed tubular networkClosed tubular network No ribosomesNo ribosomes Functions Functions
• Nutrient processingNutrient processing• Synthesis and storage of nonprotein Synthesis and storage of nonprotein
macromoleculesmacromolecules
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Golgi ApparatusGolgi Apparatus: A Packaging : A Packaging MachineMachine
Where proteins are modified and sent to their final Where proteins are modified and sent to their final destinationsdestinations
A stack of cisternaeA stack of cisternae Do not form a continuous networkDo not form a continuous network Closely associated with ER both in location and Closely associated with ER both in location and
functionfunction The ER buds off transitional vesicles (packets of The ER buds off transitional vesicles (packets of
protein) where it meets the Golgi apparatusprotein) where it meets the Golgi apparatus The Golgi apparatus picks up the transitional vesiclesThe Golgi apparatus picks up the transitional vesicles The proteins are often modified by addition of The proteins are often modified by addition of
polysaccharides and lipidspolysaccharides and lipids Then the apparatus pinches off condensing vesiclesThen the apparatus pinches off condensing vesicles
• Sent to Sent to lysosomeslysosomes• Or transported outside the cellOr transported outside the cell
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Figure 5.9
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Figure 5.10
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Figure 5.11
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MitochondriaMitochondria: Energy : Energy GeneratorsGenerators
Cellular activities require a constant supply of Cellular activities require a constant supply of energyenergy
The bulk of this energy generated by mitochondriaThe bulk of this energy generated by mitochondria Smooth, continuous outer membraneSmooth, continuous outer membrane Inner folded membrane (folds are Inner folded membrane (folds are cristaecristae))
Cristae hold enzymes and electron carriers of aerobic Cristae hold enzymes and electron carriers of aerobic respirationrespiration
Spaces around cristae filled with a Spaces around cristae filled with a matrixmatrix• RibosomesRibosomes• DNADNA• Enzymes and other compounds involved I the metabolic Enzymes and other compounds involved I the metabolic
cyclecycle Divide independently of the cellDivide independently of the cell Contain circular strands of DNAContain circular strands of DNA Contain prokaryotic-sized 70S ribosomesContain prokaryotic-sized 70S ribosomes
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Figure 5.12
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ChloroplastsChloroplasts: Photosynthesis : Photosynthesis MachinesMachines
Organelles found in algae and plant cellsOrganelles found in algae and plant cells Convert energy of sunlight into chemical Convert energy of sunlight into chemical
energy through photosynthesisenergy through photosynthesis Two membranesTwo membranes
Smooth outer membraneSmooth outer membrane Inner membrane folded in to Inner membrane folded in to thylakoidsthylakoids Thylakoids stacked upon one another into Thylakoids stacked upon one another into granagrana Contain chlorophyll and sometimes other Contain chlorophyll and sometimes other
pigmentspigments StromaStroma surrounds the thylakoids surrounds the thylakoids
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Figure 5.13
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Ribosomes: Protein Ribosomes: Protein SynthesizersSynthesizers
Some scattered in the cytoplasm and Some scattered in the cytoplasm and cytoskeletoncytoskeleton
Others associated with REROthers associated with RER Often found in chains of polyribosomes Often found in chains of polyribosomes
(polysomes)(polysomes) Composed of large and small subunits of Composed of large and small subunits of
ribonucleoproteinribonucleoprotein Larger 80S variety, composed of 60S and Larger 80S variety, composed of 60S and
40S subunits40S subunits
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The Cytoskeleton: A Support NetworkThe Cytoskeleton: A Support Network
Flexible framework of molecules criss-Flexible framework of molecules criss-crossing the cytoplasmcrossing the cytoplasm
Several functionsSeveral functions Anchoring organellesAnchoring organelles Moving RNA and vesiclesMoving RNA and vesicles Permitting shape changes and movement in Permitting shape changes and movement in
some cellssome cells Two types: Microfilaments and Two types: Microfilaments and
microtubulesmicrotubules
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MicrofilamentsMicrofilaments
Thin protein strandsThin protein strands Attach to the cell membraneAttach to the cell membrane Some responsible for movements of the Some responsible for movements of the
cytoplasmcytoplasm Some active in amoeboid motionSome active in amoeboid motion
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MicrotubulesMicrotubules
Long, hollow tubesLong, hollow tubes Maintain the shape of eukaryotic cells Maintain the shape of eukaryotic cells
without wallswithout walls Transport substancesTransport substances Responsible for the movement of cilia and Responsible for the movement of cilia and
flagellaflagella
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Figure 5.14
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5.4 The Kingdom of the 5.4 The Kingdom of the FungiFungi MyceteaeMyceteae Great variety and complexityGreat variety and complexity Approximately 100,000 speciesApproximately 100,000 species Can be divided into two groups:Can be divided into two groups:
Macroscopic fungiMacroscopic fungi Microscopic fungi:Microscopic fungi:
• YeastsYeasts Round or oval shapeRound or oval shape Unique mode of asexual reproductionUnique mode of asexual reproduction Some form pseudohyphae (false filaments)Some form pseudohyphae (false filaments)
• MoldsMolds Long, threadlike cellsLong, threadlike cells Filamentous arrangement (hyphae)Filamentous arrangement (hyphae)
• Some are dimorphic (yeast-like and filamentous forms exist)Some are dimorphic (yeast-like and filamentous forms exist) Majority are unicellular or colonialMajority are unicellular or colonial
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Figure 5.15
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Figure 5.16
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Fungal NutritionFungal Nutrition HeterotrophicHeterotrophic Acquire nutrients from Acquire nutrients from substratessubstrates Most fungi are Most fungi are saprobessaprobes Can also be Can also be parasitesparasites General method of obtaining nutritionGeneral method of obtaining nutrition
Penetrates the substratePenetrates the substrate Secretes enzymesSecretes enzymes Breaks down the enzymes into small moleculesBreaks down the enzymes into small molecules Absorbs the moleculesAbsorbs the molecules
Can absorb a wide variety of substratesCan absorb a wide variety of substrates Large medical and agricultural importanceLarge medical and agricultural importance
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Figure 5.17
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Organization of Microscopic Organization of Microscopic FungiFungi
Most grow in loose associations or coloniesMost grow in loose associations or colonies Yeasts- soft, uniform texture and appearanceYeasts- soft, uniform texture and appearance Filamentous fungal colonies- cottony, hairy, or velvety Filamentous fungal colonies- cottony, hairy, or velvety
texturestextures MyceliumMycelium- the woven, intertwining mass of hyphae that - the woven, intertwining mass of hyphae that
makes up the body or colony of a moldmakes up the body or colony of a mold Unique organizational features of hyphaeUnique organizational features of hyphae
SeptaSepta- divide the hyphae into segments (most fungi have - divide the hyphae into segments (most fungi have septate hyphae)septate hyphae)
Nonseptate hyphae- one long, continuous, multinucleate Nonseptate hyphae- one long, continuous, multinucleate cellcell
Functions of hyphaeFunctions of hyphae Vegetative hyphae (mycelia)- visible mass of growth on Vegetative hyphae (mycelia)- visible mass of growth on
the substrate surface; penetrates the substrate to digest the substrate surface; penetrates the substrate to digest and absorb nutrientsand absorb nutrients
Reproductive (fertile) hyphae- from vegetative hyphae; Reproductive (fertile) hyphae- from vegetative hyphae; responsible for the production of responsible for the production of sporesspores
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Figure 5.18
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Reproductive Strategies and Spore Reproductive Strategies and Spore FormationFormation
Most can propagate by growth of hyphae or Most can propagate by growth of hyphae or fragmentationfragmentation
Primary reproductive mode- the production of Primary reproductive mode- the production of sporesspores
Function of sporesFunction of spores MultiplicationMultiplication SurvivalSurvival Producing genetic variationProducing genetic variation DisseminationDissemination
Large diversity in spores among the fungiLarge diversity in spores among the fungi• General grouping of spores- asexual and sexualGeneral grouping of spores- asexual and sexual
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Asexual SporesAsexual Spores
SporangiosporesSporangiospores Formed by successive cleavages within the Formed by successive cleavages within the
sporangiumsporangium Sporangium attached to the sporangiophoreSporangium attached to the sporangiophore Released when the sporangium rupturesReleased when the sporangium ruptures
ConidiosporesConidiospores Aka Aka conidiaconidia Free sporesFree spores Develop either by pinching off the tip of fertile Develop either by pinching off the tip of fertile
hypha or by segmentation of a vegetative hyphahypha or by segmentation of a vegetative hypha
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Figure 5.19
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Sexual SporesSexual Spores
Increases genetic variationIncreases genetic variation Majority of fungi produce sexual spores at Majority of fungi produce sexual spores at
some pointsome point
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Fungal Identification and CultivationFungal Identification and Cultivation
Medical specimensMedical specimens Isolated on special types of mediaIsolated on special types of media Observed macroscopically and microscopicallyObserved macroscopically and microscopically
Usually use sexual spore-forming structures Usually use sexual spore-forming structures and sporesand spores
Other characteristics that contribute to Other characteristics that contribute to identificationidentification Hyphal typeHyphal type Colony texture and pigmentationColony texture and pigmentation Physiological characteristicsPhysiological characteristics Genetic makeupGenetic makeup
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The Roles of Fungi in Nature and The Roles of Fungi in Nature and IndustryIndustry
Nearly all fungi are free-living and don’t need Nearly all fungi are free-living and don’t need a hosta host
Human infection by pathogenic fungi usually Human infection by pathogenic fungi usually occurs through accidental contactoccurs through accidental contact
Humans are generally resistant to fungal Humans are generally resistant to fungal infection, except for two main typesinfection, except for two main types Primary pathogensPrimary pathogens Opportunistic pathogensOpportunistic pathogens
Mycoses vary in the way the agent enters the Mycoses vary in the way the agent enters the body and the degree of tissue involvementbody and the degree of tissue involvement
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Not only involved in infectionsNot only involved in infections AllergiesAllergies PoisoningPoisoning Agricultural damageAgricultural damage
Benefits of fungiBenefits of fungi Decomposing organic matter and returning Decomposing organic matter and returning
essential minerals to the soilessential minerals to the soil Mycorrhizae increase the ability of plant roots to Mycorrhizae increase the ability of plant roots to
absorb water and nutrientsabsorb water and nutrients Production ofProduction of
• AntibioticsAntibiotics• AlcoholAlcohol• Organic acidsOrganic acids• VitaminsVitamins
Food flavoringsFood flavorings
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5.5 The Protists5.5 The Protists
Traditionally contains the algae and Traditionally contains the algae and protozoaprotozoa
Two major taxonomic categoriesTwo major taxonomic categories Subkingdom AlgaeSubkingdom Algae Subkingdom ProtozoaSubkingdom Protozoa
Any unicellular or colonial organism that Any unicellular or colonial organism that lacks true tissueslacks true tissues
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The The AlgaeAlgae: Photosynthetic : Photosynthetic protistsprotists
Vary in length from a few micrometers to 100 Vary in length from a few micrometers to 100 metersmeters
Unicellular, colonial, and filamentous formsUnicellular, colonial, and filamentous forms Larger forms can possess tissues and simple Larger forms can possess tissues and simple
organsorgans Exhibit all eukaryotic organellesExhibit all eukaryotic organelles Chloroplasts contain chlorophyll as well as other Chloroplasts contain chlorophyll as well as other
pigmentspigments One of the main components of One of the main components of planktonplankton Rarely infectiousRarely infectious Primary medical threat: shellfish exposed to red Primary medical threat: shellfish exposed to red
tidetide
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Figure 5.21
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Biology of the ProtozoaBiology of the Protozoa
About 65,000 speciesAbout 65,000 species Most are harmless, free-living inhabitants Most are harmless, free-living inhabitants
of water and soilof water and soil Few are parasitesFew are parasites
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Protozoan Form and FunctionProtozoan Form and Function Most are single cellsMost are single cells Contain major eukaryotic organelles except Contain major eukaryotic organelles except
chloroplastschloroplasts Cytoplasm usually dividedCytoplasm usually divided
EctoplasmEctoplasm: clear outer layer involved in locomotion, : clear outer layer involved in locomotion, feeding, and protectionfeeding, and protection
Endoplasm: granular inner region housing the nucleus, Endoplasm: granular inner region housing the nucleus, mitochondria, and food and contractile vacuolesmitochondria, and food and contractile vacuoles
Some ciliates and flagellates have organelles working Some ciliates and flagellates have organelles working like a primitive nervous systemlike a primitive nervous system
No cell wall- so some flexibilityNo cell wall- so some flexibility Cell shape can remain constant or can change Cell shape can remain constant or can change
constantly (amoebas)constantly (amoebas) Size between 3 to 300 µmSize between 3 to 300 µm
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Nutritional and Habitat RangeNutritional and Habitat Range HeterotrophicHeterotrophic Usually require their food in a complex organic formUsually require their food in a complex organic form Free-living species scavenge or grazeFree-living species scavenge or graze Some have special feeding structures such as oral Some have special feeding structures such as oral
grooves; some absorb food directly through the cell grooves; some absorb food directly through the cell membranemembrane
Parasitic species live on the fluids of their host; or can Parasitic species live on the fluids of their host; or can actively feed on tissuesactively feed on tissues
Predominant habitatsPredominant habitats Fresh and marine waterFresh and marine water SoilSoil Plants Plants AnimalsAnimals
Many can convert to a resistant, dormant stage called Many can convert to a resistant, dormant stage called a cysta cyst
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Styles of LocomotionStyles of Locomotion All but the Apicomplexa are motile by means of All but the Apicomplexa are motile by means of
pseudopodspseudopods, , flagellaflagella, or , or ciliacilia Some unusual species move by gliding or twistingSome unusual species move by gliding or twisting PseudopodsPseudopods
Amoeboid motionAmoeboid motion Can serve as feeding structuresCan serve as feeding structures
FlagellaFlagella From one to severalFrom one to several Some attached along the length of the cell by the Some attached along the length of the cell by the
undulating membraneundulating membrane CiliaCilia
Mostly distributed over the entire surface of the cellMostly distributed over the entire surface of the cell Form characteristic patternsForm characteristic patterns
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Life Cycles and ReproductionLife Cycles and Reproduction
Figure 5.22
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Vary from simple to complexVary from simple to complex Some exist only in Some exist only in trophozoitetrophozoite stage stage Others alternate between trophozoite and Others alternate between trophozoite and
cystcyst Life cycle of a parasitic protozoan Life cycle of a parasitic protozoan
determines the mode of transmission to determines the mode of transmission to hostshosts
All reproduce by asexual methodsAll reproduce by asexual methods Usually mitotic cell divisionUsually mitotic cell division Some by multiple fissionSome by multiple fission
Sexual reproduction occurs during the life Sexual reproduction occurs during the life cycle of most protozoacycle of most protozoa Ciliates participate in Ciliates participate in conjugationconjugation
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Classification of Selected Medically Classification of Selected Medically Important ProtozoaImportant Protozoa
• Four groupsFour groups• Based on:Based on:
• Method of motilityMethod of motility• Mode of reproductionMode of reproduction• Stages in the lifecycleStages in the lifecycle
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MastigophoraMastigophora (Flagellated) (Flagellated) Motility primarily by flagellaMotility primarily by flagella Single nucleusSingle nucleus Sexual reproduction by syngamySexual reproduction by syngamy Division by longitudinal fissionDivision by longitudinal fission Parasitic forms tend to lack mitochondria and Parasitic forms tend to lack mitochondria and
Golgi apparatusGolgi apparatus Most form cysts and are free-livingMost form cysts and are free-living Most are solitaryMost are solitary ExamplesExamples
TrypanosomaTrypanosoma LeishmaniaLeishmania GiardiaGiardia TrichomonasTrichomonas
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Figure 5.23
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SarcodinaSarcodina (Amoebas) (Amoebas) PseudopodsPseudopods Some have flagellated reproductive statesSome have flagellated reproductive states Asexual reproduction by fissionAsexual reproduction by fission Two groups have an external shellTwo groups have an external shell Mostly uninucleateMostly uninucleate Usually encystUsually encyst Most free-livingMost free-living ExamplesExamples
EntamoebaEntamoeba ForaminiferaForaminifera RadiolariansRadiolarians
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Figure 5.24
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CiliophoraCiliophora (Ciliated) (Ciliated)
Trophozoites mobile by ciliaTrophozoites mobile by cilia Some have cilia in tufts for feeding and Some have cilia in tufts for feeding and
attachmentattachment Most develop cystsMost develop cysts Both macronuclei and micronucleiBoth macronuclei and micronuclei Division by transverse fissionDivision by transverse fission Most have definite mouth and feeding Most have definite mouth and feeding
organelleorganelle Show relatively advanced behaviorShow relatively advanced behavior Majority are free-living and harmlessMajority are free-living and harmless
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Figure 5.25
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ApicomplexaApicomplexa (Sporozoa) (Sporozoa)
Most not motile except male gametesMost not motile except male gametes Complex life cyclesComplex life cycles Produce Produce sporozoitessporozoites following sexual following sexual
reproductionreproduction Important in transmission of infectionsImportant in transmission of infections Most form oocystsMost form oocysts Entire group is parasiticEntire group is parasitic ExamplesExamples
PlasmodiumPlasmodium Toxoplasma gondiiToxoplasma gondii
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Figure 5.26
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Protozoan Identification and Protozoan Identification and CultivationCultivation
Shape and size of cellShape and size of cell Type, number, and distribution of Type, number, and distribution of
locomotor structureslocomotor structures Presence of special organelles or cystsPresence of special organelles or cysts Number of nucleiNumber of nuclei Can be cultivated on artificial media or in Can be cultivated on artificial media or in
laboratory animalslaboratory animals
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Important Protozoan PathogensImportant Protozoan Pathogens
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Pathogenic Flagellates: Pathogenic Flagellates: TrypanosomesTrypanosomes
Genus Genus TrypanosomaTrypanosoma T. bruceiT. brucei causes sleeping sickness causes sleeping sickness T. cruziT. cruzi causes Chagas disease causes Chagas disease
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Figure 5.27
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Infective Amoebas: Infective Amoebas: EntamoebaEntamoeba
Amoebiasis caused by Amoebiasis caused by Entamoeba Entamoeba histolyticahistolytica
Fourth most common protozoan infection Fourth most common protozoan infection in the worldin the world
Aka amoebic dysentery Aka amoebic dysentery
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Figure 5.28
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5.6 The Parasitic Helminths5.6 The Parasitic Helminths
Tapeworms, flukes, and roundwormsTapeworms, flukes, and roundworms Adults large enough to be seen with the Adults large enough to be seen with the
naked eyenaked eye From 1 mm to 25 m in lengthFrom 1 mm to 25 m in length Microscope is necessary to identify eggs Microscope is necessary to identify eggs
and larvaeand larvae Two major groups: Flatworms and Two major groups: Flatworms and
RoundwormsRoundworms
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FlatwormsFlatworms
Phylum PlatyhelminthesPhylum Platyhelminthes ThinThin Often segmentedOften segmented SubdivisionsSubdivisions
CestodesCestodes (tapeworms) (tapeworms) TrematodesTrematodes (flukes) (flukes)
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Figure 5.29
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RoundwormsRoundworms
Phylum AschelminthesPhylum Aschelminthes Aka Aka nematodesnematodes ElongateElongate CylindricalCylindrical UnsegmentedUnsegmented
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Figure 5.30
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General Worm MorphologyGeneral Worm Morphology
Most developed organs are those of the Most developed organs are those of the reproductive tractreproductive tract
Some degree of reduction in digestive, Some degree of reduction in digestive, excretory, nervous, and muscular systemsexcretory, nervous, and muscular systems
Most have thick cuticles for protection and Most have thick cuticles for protection and mouth glands for breaking down the host’s mouth glands for breaking down the host’s tissuetissue
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Life Cycles and ReproductionLife Cycles and Reproduction
Fertilized egg (embryo), larval, and adult stagesFertilized egg (embryo), larval, and adult stages In most, adults derive nutrients and reproduce In most, adults derive nutrients and reproduce
sexually in a host’s bodysexually in a host’s body Nematodes- separate sexesNematodes- separate sexes Trematodes- separate sexes or Trematodes- separate sexes or hermaphroditichermaphroditic
Must complete the life cycle by transmitting an Must complete the life cycle by transmitting an infective form to the body of another hostinfective form to the body of another host Larval development- intermediate (secondary) hostLarval development- intermediate (secondary) host Adulthood and mating- Adulthood and mating- definitive (final) hostdefinitive (final) host
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A Helminth Cycle: The A Helminth Cycle: The PinwormPinworm
Person swallows microscopic eggsPerson swallows microscopic eggs Picked up from another infected person by direct Picked up from another infected person by direct
contactcontact Or by touching articles an infected person has touchedOr by touching articles an infected person has touched
Eggs hatch in the intestineEggs hatch in the intestine Release larvae that mature in to adult worms (about Release larvae that mature in to adult worms (about
1 month)1 month) Male and female worms mateMale and female worms mate Female migrates out of the anus to deposit eggs Female migrates out of the anus to deposit eggs
Causes intense itchinessCauses intense itchiness Relieved by scratchingRelieved by scratching Scratching contaminates the fingers which transfer the Scratching contaminates the fingers which transfer the
eggseggs Eggs spread to others or the original host reinfects Eggs spread to others or the original host reinfects
him or herselfhim or herself
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Helminth Classification and Helminth Classification and IdentificationIdentification
ShapeShape SizeSize Degree of development of various organsDegree of development of various organs Presence of hooks, suckers, or other Presence of hooks, suckers, or other
special structuresspecial structures Mode of reproductionMode of reproduction Kinds of hostsKinds of hosts Appearance of eggs and larvaeAppearance of eggs and larvae
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Distribution and Importance of Distribution and Importance of Parasitic WormsParasitic Worms
About 50 species parasitize humansAbout 50 species parasitize humans Distributed in all areas of the worldDistributed in all areas of the world Yearly estimate of worldwide infections- in Yearly estimate of worldwide infections- in
the billionsthe billions