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Viruses, Bacteria & Archaea
Chapter 21
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
OutlineOutline
VirusesViruses StructureStructure
ClassificationClassification
ReproductionReproduction
ProkaryotesProkaryotes StructureStructure
ReproductionReproduction
NutritionNutrition
BacteriaBacteria
ArchaeaArchaea
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
The VirusesThe VirusesViruses are noncellular and thus cannot be Viruses are noncellular and thus cannot be classified with cellular organismsclassified with cellular organisms
Generally smaller than 200 nm in diameterGenerally smaller than 200 nm in diameter
Each type has at least two partsEach type has at least two partsCapsid: Outer layer composed of protein Capsid: Outer layer composed of protein subunitssubunits
Some enveloped by membraneSome enveloped by membrane
Others “naked”Others “naked”
Nucleic acid core: DNA or RNANucleic acid core: DNA or RNA
Vary in shape from thread-like to Vary in shape from thread-like to polyhedralpolyhedral
4Viruses
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Viral CategorizationViral Categorization
Classification is based on:Classification is based on:Type of nucleic acidType of nucleic acid
Size and shapeSize and shape
Presence / absence of outer envelopePresence / absence of outer envelope
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Parasitic NatureParasitic Nature
Viruses are:Viruses are:Obligate intracellular parasitesObligate intracellular parasites
Cannot reproduce outside a living cellCannot reproduce outside a living cell
Can be cultured only inside living cellsCan be cultured only inside living cells
Chicken egg Chicken egg
Tissue cultureTissue culture
7“Growing” Viruses
Viruses, BacterViruses, Bacteria & Archaeaia & ArchaeaThe Bacteriophages:The Bacteriophages:
ReproductionReproduction
Bacteriophages – Viruses that infect Bacteriophages – Viruses that infect bacterial cellsbacterial cells
Portions of capsid adhere to specific Portions of capsid adhere to specific receptor on the host cellreceptor on the host cell
Viral nucleic acid enters the cellViral nucleic acid enters the cell
Once inside, the virus takes over Once inside, the virus takes over metabolic machinery of the host cellmetabolic machinery of the host cell
Viruses, BacterViruses, Bacteria & Archaeaia & ArchaeaBacteriophages:Bacteriophages:
The Lytic CycleThe Lytic Cycle
Lytic cycle may be divided into five Lytic cycle may be divided into five stages:stages:AttachmentAttachment
PenetrationPenetration
BiosynthesisBiosynthesis
MaturationMaturation
ReleaseRelease
Viruses, BacterViruses, Bacteria & Archaeaia & ArchaeaThe Bacteriophages:The Bacteriophages:
The Lysogenic CycleThe Lysogenic Cycle
Phage becomes a prophagePhage becomes a prophageBecomes integrated into the host Becomes integrated into the host genomegenome
Becomes latentBecomes latent
May later reenter the lytic cycleMay later reenter the lytic cycle
11Lytic and Lysogenic Cycles in Prokaryotes
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Reproduction of Animal VirusesReproduction of Animal Viruses
Animal virus enters the host cellAnimal virus enters the host cell
Uncoating releases viral DNA or RNAUncoating releases viral DNA or RNABudding:Budding:
Viral particles released in a budViral particles released in a bud
Acquires a membranous envelopeAcquires a membranous envelope
Retroviruses (AIDS)Retroviruses (AIDS)
Contain reverse transcriptaseContain reverse transcriptase
Carries out RNA Carries out RNA cDNA reverse cDNA reverse transcriptiontranscription
cDNA becomes integrated into host DNAcDNA becomes integrated into host DNA
13Reproduction of the Retrovirus HIV-1
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Viral InfectionsViral InfectionsViruses are best known for causing Viruses are best known for causing infectious diseases in plants and animalsinfectious diseases in plants and animals Herpes, HIV, cancerHerpes, HIV, cancer
Viruses lack metabolism; thus, antibiotics Viruses lack metabolism; thus, antibiotics have no effecthave no effect
ViroidsViroids
Naked strands of RNANaked strands of RNA
Many crop diseasesMany crop diseases
PrionsPrions
Protein molecules with contagious tertiary Protein molecules with contagious tertiary structurestructure
Some human and other animal diseases - Mad Some human and other animal diseases - Mad cow diseasecow disease
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
The ProkaryotesThe Prokaryotes
Include bacteria and archaea, which Include bacteria and archaea, which are fully functioning cellsare fully functioning cellsA single spoonful of earth can contain A single spoonful of earth can contain >1000 prokaryotes>1000 prokaryotes
Range in size from 1-10 Range in size from 1-10 µµm in length m in length and 0.7-1.5 and 0.7-1.5 µµm in widthm in width
16Pasteur’s Experiment
17Bacterial Structure
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Prokaryote StructureProkaryote Structure
Lack a membrane-bounded nucleus Lack a membrane-bounded nucleus (DNA in nucleoid region)(DNA in nucleoid region)
Outer cell wall containing Outer cell wall containing peptidoglycanpeptidoglycan
Some move by means of flagellaSome move by means of flagella
Lack membranous organellesLack membranous organelles
May have accessory ring of DNA May have accessory ring of DNA (plasmid)(plasmid)
19Flagella
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Reproduction in ProkaryotesReproduction in Prokaryotes
AsexualAsexualProkaryotes reproduce asexually by Prokaryotes reproduce asexually by means of binary fissionmeans of binary fission
Methods of genetic recombinationMethods of genetic recombinationConjugationConjugation
Sex pilus forms between two cellsSex pilus forms between two cells
Donor cell passes DNA to recipient cell Donor cell passes DNA to recipient cell through pilusthrough pilus
TransformationTransformation
TransductionTransduction
21Fimbriae and Sex Pilus
22Binary Fission
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Reproduction in ProkaryotesReproduction in Prokaryotes
TransformationTransformationOccurs when bacterium picks up free Occurs when bacterium picks up free pieces of DNA from other prokaryotespieces of DNA from other prokaryotes
Becomes incorporated into genomeBecomes incorporated into genome
TransductionTransductionOccurs when bacteriophages carry Occurs when bacteriophages carry portions of bacterial DNA from one cell to portions of bacterial DNA from one cell to anotheranother
Serve as vectorsServe as vectors
Some bacteria form resistant endospores Some bacteria form resistant endospores under unfavorable conditionsunder unfavorable conditions
24The Endospore of Clostridium tetani
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Prokaryotic NutritionProkaryotic Nutrition
Oxygen requirements:Oxygen requirements:Obligate aerobes – unable to grow in Obligate aerobes – unable to grow in the absence of free oxygenthe absence of free oxygen
Obligate anaerobes – unable to grow Obligate anaerobes – unable to grow in the presence of free oxygenin the presence of free oxygen
Facultative anaerobes – able to grow Facultative anaerobes – able to grow in either the presence or absence of in either the presence or absence of free oxygenfree oxygen
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Autotrophic ProkaryotesAutotrophic Prokaryotes
PhotoautotrophsPhotoautotrophsUse solar energy to reduce carbon Use solar energy to reduce carbon dioxide to organic compoundsdioxide to organic compounds
PhotosyntheticPhotosynthetic
ChemoautotrophsChemoautotrophsOxidize inorganic compounds to obtain Oxidize inorganic compounds to obtain the necessary energythe necessary energy
Use it to reduce COUse it to reduce CO22 to an organic to an organic compoundcompound
ChemosyntheticChemosynthetic
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Heterotrophic ProkaryotesHeterotrophic Prokaryotes
Most prokaryotes are chemoheterotrophs Most prokaryotes are chemoheterotrophs that take in organic nutrientsthat take in organic nutrientsAerobic saprotrophs decompose most Aerobic saprotrophs decompose most large organic molecules to smaller large organic molecules to smaller moleculesmolecules
Essential components of healthy Essential components of healthy ecosystemecosystem
May be free-living or symbioticMay be free-living or symbioticNitrogen fixationNitrogen fixation
CommensalismCommensalism
ParasitesParasites
28Nodules of a Legume
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
The BacteriaThe Bacteria
Bacteria are commonly diagnosed Bacteria are commonly diagnosed using the Gram stain procedureusing the Gram stain procedure
When washed after staining:When washed after staining:Gram-positive bacteria retain dye and Gram-positive bacteria retain dye and appear purpleappear purple
Gram-negative bacteria do not retain Gram-negative bacteria do not retain dye and appear pinkdye and appear pink
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
The BacteriaThe Bacteria
Structure of cell wall also of Structure of cell wall also of diagnostic usediagnostic use
Bacteria can be further classified in Bacteria can be further classified in terms of their three basic shapesterms of their three basic shapesSpiral (spirilli),Spiral (spirilli),
Rod (bacilli), andRod (bacilli), and
Round (cocci)Round (cocci)
31Diversity of Bacteria
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
CyanobacteriaCyanobacteria
Formerly called the Blue-Green algae Formerly called the Blue-Green algae (Cyanophyta)(Cyanophyta)
Cyanobacteria are Gram-negative Cyanobacteria are Gram-negative bacteria that photosynthesizebacteria that photosynthesize
Believed to be responsible for Believed to be responsible for introducing oxygen into the primitive introducing oxygen into the primitive atmosphereatmosphereLack visible means of locomotionLack visible means of locomotion
Can live in extreme environmentsCan live in extreme environments
When commensals with fungi, form When commensals with fungi, form lichenslichens
33Diversity Among the Cyanobacteria
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
The ArchaeaThe ArchaeaArchaea were earlier considered Archaea were earlier considered bacteriabacteria
Carl Woese discovered that the base Carl Woese discovered that the base sequence of their rRNA differs from sequence of their rRNA differs from BacteriaBacteria
Other differences:Other differences:Archaea do not have peptidoglycan in Archaea do not have peptidoglycan in their cell walls like the Bacteriatheir cell walls like the Bacteria
Archaea biochemical more like Eukarya Archaea biochemical more like Eukarya than Bacteriathan Bacteria
Archaea now thought to be more Archaea now thought to be more closely related to Eukarya than to closely related to Eukarya than to BacteriaBacteria
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Archaea MetabolismArchaea Metabolism
Most are chemoautotrophsMost are chemoautotrophs
Some mutualisticSome mutualistic
Some commensalisticSome commensalistic
None known to be parasiticNone known to be parasitic
None are photosyntheticNone are photosynthetic
Many live in harsh conditionsMany live in harsh conditions
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
Types of ArchaeaTypes of ArchaeaMany live in harsh conditions:Many live in harsh conditions:
Anaerobic marshesAnaerobic marshes MethanogensMethanogens Produce methane from hydrogen gas and Produce methane from hydrogen gas and carbon dioxidecarbon dioxide
Salty lakesSalty lakes HalophilesHalophiles Require high salt concentrations for growth, Require high salt concentrations for growth, andand
Hot sulfur springsHot sulfur springs ThermoacidophilesThermoacidophiles Reduce sulfides and survive best at Reduce sulfides and survive best at temperatures above 80ºCtemperatures above 80ºC
Plasma membranes contain unusual lipids Plasma membranes contain unusual lipids convey tolerance of high temperaturesconvey tolerance of high temperatures
37Thermoacidophile Habitat and Structure
Viruses, BacterViruses, Bacteria & Archaeaia & Archaea
ReviewReview
VirusesViruses StructureStructure
ClassificationClassification
ReproductionReproduction
ProkaryotesProkaryotes StructureStructure
ReproductionReproduction
NutritionNutrition
BacteriaBacteria
ArchaeaArchaea
Viruses, Bacteria & Archaea
Ending Slide Chapter 21