Chapter 19Chapter 19Prokaryotes and Prokaryotes and VirusesViruses

Chapter 19 2

Prokaryotic DomainsProkaryotic DomainsSingle-cell microbesSingle-cell microbes

Lack most organelles (membrane bound)Lack most organelles (membrane bound)

Inhabit diverse environmentsInhabit diverse environments

Differences between Bacteria and ArchaeaDifferences between Bacteria and Archaea• Structural and biochemical featuresStructural and biochemical features

– Archaea have histones (just like Eukarya)Archaea have histones (just like Eukarya)– Differences in cell walls, plasma membrane Differences in cell walls, plasma membrane

composition, ribosomes, and RNA polymerasescomposition, ribosomes, and RNA polymerases

Chapter 19 3

The Sizes of MicroorganismsThe Sizes of Microorganisms11µµmm

Eukaryotic CellsEukaryotic Cells(10-100 (10-100 µµm)m)

Prokaryotic CellsProkaryotic Cells(0.2-10 (0.2-10 µµm)m)

StaphylococcusStaphylococcus

CyanobacteriumCyanobacterium

Escherichia coliEscherichia coli

VirusesViruses(0.05-0.2 (0.05-0.2 µµm)m)

Chapter 19 4 Classifying Prokaryotes Is DifficultClassifying Prokaryotes Is Difficult

Features used in prokaryotic Features used in prokaryotic classification:classification:• ShapeShape•Means of locomotionMeans of locomotion• PigmentsPigments• Nutrient requirementsNutrient requirements• Colony appearanceColony appearance• Gram staining characteristicsGram staining characteristics• Nucleotide sequencesNucleotide sequences

Chapter 19 5

Three Common Bacterial ShapesThree Common Bacterial Shapes

(a)(a)(a)(a) (b)(b)(b)(b)

(c)(c)(c)(c)

Chapter 19 6

Bacterial CharacteristicsBacterial CharacteristicsShape - cocci, bacilli, spirillaShape - cocci, bacilli, spirilla• Cell wall - peptidoglycanCell wall - peptidoglycan• Capsules or slime layer - polysaccharide or protein Capsules or slime layer - polysaccharide or protein

chainschains• Pili - protein form of attachmentPili - protein form of attachment• Flagella - used to propel by rotationFlagella - used to propel by rotation

Endospores (some bacteria)Endospores (some bacteria)• Contain nucleic acid surrounded by a protein coatContain nucleic acid surrounded by a protein coat• Form in inhospitable environmentsForm in inhospitable environments• Reside dormant until favorable environment; Can Reside dormant until favorable environment; Can

last for yearslast for years• Great mechanism for continuing speciesGreat mechanism for continuing species

Chapter 19 7

Chapter 19 8 Diverse MetabolismsDiverse Metabolisms

Anaerobic MetabolismAnaerobic Metabolism• Some bacteria live without oxygen (and are Some bacteria live without oxygen (and are

poisoned by it)poisoned by it)– e.g. Tetanus bacteriae.g. Tetanus bacteria• Some bacteria can switch between aerobic Some bacteria can switch between aerobic

and anaerobic respirationand anaerobic respiration– e.g. e.g. Escherichia coliEscherichia coli in our large intestines in our large intestines

Chapter 19 9 Diverse MetabolismsDiverse Metabolisms

Where bacteria get their energyWhere bacteria get their energy• Familiar organic compoundsFamiliar organic compounds

– Sugars, carbohydrates, fats, and proteinsSugars, carbohydrates, fats, and proteins• Compounds poisonous to humansCompounds poisonous to humans

– Petroleum, methane, benzene, toluenePetroleum, methane, benzene, toluene• Inorganic moleculesInorganic molecules

– Hydrogen, sulfur, ammonia, iron, nitriteHydrogen, sulfur, ammonia, iron, nitrite

Some bacteria get energy from sunlightSome bacteria get energy from sunlight• CyanobacteriaCyanobacteria perform photosynthesis perform photosynthesis• Sulfur bacteria use HSulfur bacteria use H22S instead of water in S instead of water in

photosynthesisphotosynthesis

Chapter 19 10 Binary FissionBinary Fission

Asexual cell division produces identical Asexual cell division produces identical copiescopies

Binary fission can occur every 20 Binary fission can occur every 20 minutesminutes

Rapid reproductive rate allows for rapid Rapid reproductive rate allows for rapid evolutionevolution•Mutations in DNA replication are rapidly Mutations in DNA replication are rapidly

spreadspread

Chapter 19 11

Chapter 19 12 Exchange of Genetic MaterialExchange of Genetic Material

ConjugationConjugation allows for DNA transfer allows for DNA transfer between donor and recipientbetween donor and recipient

Sex pilusSex pilus connects donor to recipient connects donor to recipient cell forming a cytoplasmic bridgecell forming a cytoplasmic bridge

Conjugation can occur between Conjugation can occur between different speciesdifferent species

Small circular DNA molecules (Small circular DNA molecules (plasmidsplasmids) ) carry genes from donor to recipientcarry genes from donor to recipient

Chapter 19 13

Conjugation:Conjugation:Prokayotic “Mating”Prokayotic “Mating”

Sex PilusSex PilusSex PilusSex Pilus

DonorDonorDonorDonor

RecipientRecipientRecipientRecipient

Chapter 19 14

Benefits of BacteriaBenefits of BacteriaCyanobacteriaCyanobacteria• PhotosynthesisPhotosynthesis• Pioneers in primary successionPioneers in primary succession

Chemosynthesis - nutrient cycles and plantsChemosynthesis - nutrient cycles and plantsSymbiosis - living togetherSymbiosis - living together• Ruminants’ digestive tractsRuminants’ digestive tracts• Nitrogen fixing in certain legumesNitrogen fixing in certain legumes• Bacteria on the human bodyBacteria on the human body

Biodegradation - oilBiodegradation - oilFood production - cheese, yogurt, sauerkrautFood production - cheese, yogurt, sauerkrautDecomposersDecomposers

Chapter 19 15

Bacterial PathogensBacterial PathogensSmall number of species cause diseaseSmall number of species cause diseaseSurvey of human bacterial diseasesSurvey of human bacterial diseases• Anaerobes - toxins (tetanus, botulism)Anaerobes - toxins (tetanus, botulism)• Allergic reactions - Allergic reactions - Streptococcus Streptococcus

pneumoniaepneumoniae– PneumoniaPneumonia– "Flesh-eating" bacteria"Flesh-eating" bacteria• Black Death, tuberculosisBlack Death, tuberculosis• Sexually transmitted diseasesSexually transmitted diseases

– GonorrheaGonorrhea– SyphilisSyphilis

Chapter 19 16

The ProkaryoteThe ProkaryoteFlagellum (b)Flagellum (b)

Chapter 19 17

Bacterial HabitsBacterial Habits

HabitatsHabitats

• Bacteria inhabit nearly every habitatBacteria inhabit nearly every habitat

• Bacteria are specialistsBacteria are specialists

Chapter 19 18

ArchaeaArchaea

Unique lipid membranes, cell walls, and Unique lipid membranes, cell walls, and rRNArRNA

MethanogensMethanogens• Convert COConvert CO22 to methane to methane• Swamps, hot springs, vent communities, cow Swamps, hot springs, vent communities, cow

stomachsstomachsHalophiles - survive concentrated salt Halophiles - survive concentrated salt environmentenvironment

Thermoacidophiles - thrive in hot, acidic Thermoacidophiles - thrive in hot, acidic environmentenvironment

Chapter 19 19

Some ProkaryotesSome ProkaryotesThrive in Extreme ConditionsThrive in Extreme Conditions

Chapter 19 20

Nitrogen-Fixing BacteriaNitrogen-Fixing Bacteriaon Root Noduleson Root Nodules

(a)(a)(a)(a)

(b)(b)(b)(b)

Chapter 19 21

Nonliving Parasitic MoleculesNonliving Parasitic MoleculesVirusesViruses• Nucleic acid molecule surrounded by a protein Nucleic acid molecule surrounded by a protein

coatcoat• Bacteriophages; viruses that infect bacteriaBacteriophages; viruses that infect bacteria• Survey of human viral diseasesSurvey of human viral diseases

ViroidsViroids• Short strands of RNA without a protein coatShort strands of RNA without a protein coat• Cause disease mostly in plants; affect some cropsCause disease mostly in plants; affect some crops

PrionsPrions• Proteinaceous infectious particleProteinaceous infectious particle• Human prion diseasesHuman prion diseases

Chapter 19 22 VirusesViruses

Two major components constitute a virusTwo major components constitute a virus• Single or double-stranded DNA or RNA as Single or double-stranded DNA or RNA as

hereditary materialhereditary material• Protein coat Protein coat

– May be surrounded by an envelope formed May be surrounded by an envelope formed from the plasma membrane of the host cellfrom the plasma membrane of the host cell

Cannot grow or reproduce on their own Cannot grow or reproduce on their own and are parasites of living cellsand are parasites of living cells

Have a specialized protein coat that Have a specialized protein coat that enables entry into a enables entry into a hosthost cell… cell…

Chapter 19 23 VirusesViruses

Viral genetic material “hijacks” host cell Viral genetic material “hijacks” host cell to produce new viral componentsto produce new viral components

Viral components assemble rapidly into Viral components assemble rapidly into new viruses and burst from host cellnew viruses and burst from host cell

Chapter 19 24

Viral Structure and ReplicationViral Structure and Replication(a)(a) (b)(b)

GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins

EnvelopeEnvelope(lipid bilayer)(lipid bilayer)

EnvelopeEnvelope(lipid bilayer)(lipid bilayer)

ProteinProteinCoatCoat

ProteinProteinCoatCoat

CoreCoreProteinsProteins

CoreCoreProteinsProteins

ReverseReverseTranscriptaseTranscriptase

ReverseReverseTranscriptaseTranscriptase

Viral RNA inViral RNA inprotein coatprotein coatViral RNA inViral RNA inprotein coatprotein coat

SpikesSpikesSpikesSpikes

Herpes VirusesHerpes VirusesHIVHIVHIVHIV

Chapter 19 25

Viruses Come in Many ShapesViruses Come in Many Shapes

RabiesRabiesRabiesRabies

MeaslesMeaslesMeaslesMeasles

BacteriophageBacteriophageBacteriophageBacteriophage

HerpesHerpesHerpesHerpes

TobaccoTobaccoMosaicMosaic

TobaccoTobaccoMosaicMosaic

Chapter 19 26 Viruses Are Host-SpecificViruses Are Host-Specific

Each viral type specialized to attack Each viral type specialized to attack specific host cellspecific host cell

Bacteriophages can treat bacterial diseases Bacteriophages can treat bacterial diseases • Rise in bacterial antibiotic resistance makes Rise in bacterial antibiotic resistance makes

standard drugs less effectivestandard drugs less effective• Bacteriophages specifically target host Bacteriophages specifically target host

bacteriabacteria• Bacteriophages are harmless to human body Bacteriophages are harmless to human body

cellscells

Chapter 19 27 Viruses Are Host-SpecificViruses Are Host-Specific

In multicellular organisms viruses In multicellular organisms viruses specialize in attacking particular cell specialize in attacking particular cell typestypes

Cold virusesCold viruses attack membranes of attack membranes of respiratory tractrespiratory tract

Measles virusesMeasles viruses infect the skin infect the skinRabies virusesRabies viruses attack nerve cells attack nerve cells

Chapter 19 28 Viruses Are Host-SpecificViruses Are Host-Specific

Some viruses linked to cancer (e.g. T-cell Some viruses linked to cancer (e.g. T-cell leukemia, liver cancer, cervical cancer)leukemia, liver cancer, cervical cancer)

Herpes virusHerpes virus attacks mucous membranes attacks mucous membranes of mouth and lips (causing cold sores)of mouth and lips (causing cold sores)•Other herpes virus type causes Other herpes virus type causes

genital soresgenital soresHIV virusHIV virus attacks specific white blood attacks specific white blood cell type, causing AIDScell type, causing AIDS

Chapter 19 29

Some Viruses Infect BacteriaSome Viruses Infect Bacteria

BacteriumBacterium

Newly formingNewly formingbacteriophagesbacteriophages

Chapter 19 30

How Viruses Replicate:How Viruses Replicate:HIV (a)HIV (a)

cytoplasmcytoplasm

nucleusnucleus

DNADNAvRNAvRNA

mRNAmRNA

1a. Virus attaches to receptor

2. Viral reverse transcriptase makes DNA using viral RNA

1b.Core disintegrates; viral RNA enters the cytoplasm

3a. DNA enters nucleus & chromosomes

3b. DNA transcribed into mRNA & viral RNA, which move to cytoplasm

Chapter 19 31

How Viruses Replicate:How Viruses Replicate:HIV (b)HIV (b)

4.Viral proteins madeusing mRNA

5.Viral proteins & RNAassembled

6.Viruses bud fromplasma membrane

Chapter 19 32

How Viruses Replicate:How Viruses Replicate:Herpes (a)Herpes (a)

(cytoplasm)

envelopecoat

DNA

nucleus

DNA

mRNA

1. Virus enters cell by endocytosis 3. Viral DNA transcribed to mRNA,

which moves to cytoplasm

2a. Viral envelope merges with nuclear membrane

2b.Protein coat disintegrates; viral DNA copied & enters nucleus

Chapter 19 33

How Viruses Replicate:How Viruses Replicate:Herpes (b)Herpes (b)

nucleus

mRNA

(cytoplasm)

envelopecoat

DNA DNA

mRNA

4. MRNA makes proteins, which enter nucleus

5.New viruses assembled & bud from nucleus, get envelope from inner nuclear membrane

6.Newly formed viruses leave the cell by exocytosis

Chapter 19 34

Viral Infections Are Difficult to TreatViral Infections Are Difficult to Treat

Antibiotics against bacteria are infective Antibiotics against bacteria are infective against virusesagainst viruses

Antiviral drugs may also kill host cellsAntiviral drugs may also kill host cellsViruses “hide” within cells, are hard to Viruses “hide” within cells, are hard to detectdetect

Viruses have high mutation ratesViruses have high mutation rates•Mutations can confer resistance to Mutations can confer resistance to

antiviral drugantiviral drug• Resistant viruses spread and multiply, Resistant viruses spread and multiply,

rendering drug ineffectiverendering drug ineffective

Chapter 19 35 ViroidsViroids

ViroidsViroids are infectious particles with only are infectious particles with only short RNA strands (no protein coat)short RNA strands (no protein coat)

Able to enter host cell nucleus and direct Able to enter host cell nucleus and direct new viroid synthesisnew viroid synthesis

A number of crop diseases are caused by A number of crop diseases are caused by viroidsviroids• e.g. cucumber pale fruit disease, avocado e.g. cucumber pale fruit disease, avocado

sunblotch, potato spindle tuber diseasesunblotch, potato spindle tuber disease

Chapter 19 36 PrionsPrions

A mutated protein that acts as an A mutated protein that acts as an infectious agentinfectious agent

Fatal degenerative disease discovered Fatal degenerative disease discovered in New Guinea tribe (Fore) in 1950in New Guinea tribe (Fore) in 1950

Kuru Kuru causes loss of coordination, causes loss of coordination, dementia, deathdementia, death

Kuru in the Fore tribe was transmitted Kuru in the Fore tribe was transmitted by ritual cannibalism of the deadby ritual cannibalism of the dead

Chapter 19 37 PrionsPrions

Other diseases like kuru include:Other diseases like kuru include:• Creutzfeldt-JacobCreutzfeldt-Jacob (CJD) disease in (CJD) disease in

humanshumans• ScrapieScrapie in sheep in sheep• Bovine spongiform encephalopathyBovine spongiform encephalopathy (BSE or (BSE or

“Mad Cow Disease”) in cattle“Mad Cow Disease”) in cattle

These diseases create holes in brain These diseases create holes in brain tissuetissue

Chapter 19 38

Prions: Puzzling ProteinsPrions: Puzzling Proteins

Chapter 19Chapter 19

The EndThe End