Prokaryotes and Viruses

Prokaryotes and Prokaryotes and VirusesViruses

11

West Nile VirusWest Nile Virus

22

West Nile VirusWest Nile Virus

One of several One of several mosquito-borne mosquito-borne viruses viruses in the United States that can in the United States that can infect peopleinfect people

The virus exists in nature primarily The virus exists in nature primarily through a transmission cycle through a transmission cycle involving involving mosquitoes and birds.mosquitoes and birds.

Mosquitoes become infected with Mosquitoes become infected with West Nile virus (WNV) when they West Nile virus (WNV) when they feed on feed on infected birdsinfected birds

33

West Nile Virus SymptomsWest Nile Virus Symptoms Majority of people that become infected Majority of people that become infected

with the West Nile virus have with the West Nile virus have no illness or no illness or experience only a mild flu-like illnessexperience only a mild flu-like illness

May include May include fever, headache and body fever, headache and body aches aches lasting only a few dayslasting only a few days

Some persons may also have a Some persons may also have a mild rash mild rash or swollen lymph glandsor swollen lymph glands

Less than one percent of those infected Less than one percent of those infected may develop may develop meningitis or encephalitismeningitis or encephalitis, , the most severe forms of the diseasethe most severe forms of the disease

44

Alexander the Great, 336 B.C., Alexander the Great, 336 B.C., conquered a vast empireconquered a vast empire

It’s speculated that his demise was It’s speculated that his demise was due to West Nile encephalitisdue to West Nile encephalitis

There is still There is still no human vaccine no human vaccine for for West Nile virusWest Nile virus

How Long has the West Nile How Long has the West Nile Virus Been Around?Virus Been Around?

55

West Nile Virus is West Nile Virus is pathogenicpathogenic, it , it invades its host and multiplies, invades its host and multiplies, causing diseasecausing disease

It’s a It’s a flavivirusflavivirus, traveling inside , traveling inside mosquitoes which act as the mosquitoes which act as the transferring agent from host to hosttransferring agent from host to host

West Nile Virus Takes OffWest Nile Virus Takes Off

66


77


88

Impacts, Issues VideoImpacts, Issues Video

West Nile Virus Takes Off

99

Microorganisms Microorganisms

Single-celled organisms that are too Single-celled organisms that are too

small to be seen without a small to be seen without a

microscopemicroscope

Bacteria are the smallest living Bacteria are the smallest living

organismsorganisms

Viruses are smaller but are not aliveViruses are smaller but are not alive

1010

The ProkaryotesThe Prokaryotes

Only two groupsOnly two groups

Archaebacteria and EubacteriaArchaebacteria and Eubacteria

Arose before the eukaryotesArose before the eukaryotes

1111

Prokaryotic CharacteristicsProkaryotic Characteristics

No membrane-bound No membrane-bound

nucleusnucleus

Single chromosomeSingle chromosome

Cell wall (in most species)Cell wall (in most species)

Prokaryotic fissionProkaryotic fission

Metabolic diversityMetabolic diversity

1212

Prokaryotic Body PlanProkaryotic Body Plan

bacterial flagellum pilus

capsule

cell wall

plasma membrane

cytoplasm

DNA

ribosomes in cytoplasm

1313

pilus

bacterial flagellum

cell wall

outer capsule

plasmamembrane

cytoplasm, with

ribosomesDNA, in nucleoid


1414

Prokaryotic body plan


1515

Bacterial ShapesBacterial Shapes

coccus bacillus

spirillum

1616


1717

Bacterial Bacterial ShapesShapes

1818


1919

sex pilus

Bacterial Bacterial ShapesShapes

2020

Metabolic DiversityMetabolic Diversity

PhotoautotrophsPhotoautotrophs

ChemoautotrophsChemoautotrophs

ChemoheterotrophsChemoheterotrophs

2121

Gram StainGram Stain

2222

Gram stain

Gram StainGram Stain

2323

Bacterial GenesBacterial Genes

Bacteria have a single chromosomeBacteria have a single chromosome Circular molecule of DNACircular molecule of DNA

Many bacteria also have plasmidsMany bacteria also have plasmids Self-replicating circle of DNA that Self-replicating circle of DNA that

has a few geneshas a few genes Can be passed from one cell to Can be passed from one cell to

anotheranother

2424

Prokaryotic FissionProkaryotic Fission

2525


2727


2828


2929


3030


3131


3232


3333

parent DNA molecule DNA copy

DNA replication completed

DNA replication

begins

Bacterium before DNA replication

bacterial chromosome

3434

Membrane growth moves DNA molecules

apart

New membrane and cell-wall

material deposited

Cytoplasm divided in two

3535

Prokaryotic fission

Prokaryotic Fission - 3Prokaryotic Fission - 3

3636

ConjugatioConjugationn

Transfer of plasmid

3737

nicked plasmidconjugation tube

Prokaryotic conjugation

ConjugationConjugation

3939

Prokaryotic ClassificationProkaryotic Classification

EUBACTERIA(Bacteria)

ARCHAEBACTERIA(Archaea)

EUKARYOTES(Eukarya)

•Traditionally classified by numerical taxonomy•Now increased use of comparative biochemistry

4040

DOMAIN BACTERIA DOMAIN BACTERIA

to ancestors of eukaryotic cells

biochemical and molecular origin of life

Prokaryotic ClassificationProkaryotic Classification

4141

EubacteriaEubacteria

Includes most familiar bacteriaIncludes most familiar bacteria

Have fatty acids in plasma membraneHave fatty acids in plasma membrane

Most have cell wall; always includes Most have cell wall; always includes

peptidoglycanpeptidoglycan

Classification based largely on metabolismClassification based largely on metabolism

4242

Eubacterial DiversityEubacterial Diversity

Photoautotrophic Photoautotrophic Aerobic (Cyanobacteria)Aerobic (Cyanobacteria) Anaerobic (Green bacteria)Anaerobic (Green bacteria)

ChemoautotrophicChemoautotrophic Important in nitrogen cycleImportant in nitrogen cycle

Chemoheterotrophic Chemoheterotrophic Largest groupLargest group

4343

Examples of eubacteria

EubacteriaEubacteria

4444


4545


4646


4747

Some Pathogenic Some Pathogenic EubacteriaEubacteria

Most are Most are chemoheterotrophschemoheterotrophs E. coliE. coli strains strains Clostridium botulinumClostridium botulinum Clostridium tetanusClostridium tetanus Borrelia burgdorferiBorrelia burgdorferi RickettsiaRickettsia rickettsiirickettsii

4848

resting spore

heterocyst

photo-synthetic cell

Some Some Pathogenic Pathogenic EubacteriaEubacteria

4949

Some Some PathogeniPathogeni

c c EubacteriEubacteri

aa

5050


5151

DNA

spore coat

capsule around cell wall


5252

Bacterial BehaviorBacterial Behavior

Bacteria move toward nutrient-rich Bacteria move toward nutrient-rich regions regions

Aerobes move toward oxygen; Aerobes move toward oxygen; anaerobes avoid it anaerobes avoid it

Photosynthetic types move toward lightPhotosynthetic types move toward light Magnetotactic bacteria swim downwardMagnetotactic bacteria swim downward Myobacteria show collective behavior Myobacteria show collective behavior

5353

Bacterial BehaviorBacterial Behavior

5454

ArchaebacteriaArchaebacteria

5555

ArchaebacteriaArchaebacteria

MethanogensMethanogens

Extreme halophilesExtreme halophiles

Extreme thermophilesExtreme thermophiles

5656


5757


5858

Extreme HalophilesExtreme Halophiles

5959

Extreme ThermophilesExtreme Thermophiles

6060

Extreme ThermophilesExtreme Thermophiles

6161

VirusVirus

Noncellular infectious agentNoncellular infectious agent

Protein wrapped around a nucleic Protein wrapped around a nucleic acid coreacid core

Cannot reproduce itself; can only Cannot reproduce itself; can only be reproduced using a host cellbe reproduced using a host cell

6262

Viral Body Viral Body PlansPlans

Genetic material is Genetic material is DNA or RNADNA or RNA

Coat is protein Coat is protein

Complex virus (bacteriophage)

Polyhedral virusHelical virus6363

Enveloped Virus (HIV)Enveloped Virus (HIV)

lipid envelope (derived from host)

viral RNA

reverse transcriptaseviral coat (proteins)

viral protein

6464

viral RNA

protein subunits of coat

18 nm diameter, 250 nm length

Enveloped Enveloped Virus (HIV)Virus (HIV)

6565

80 nm diameter


6666

DNA

protein coat

sheath

base plate

tail fiber

65–nm diameter head, 225 nm total length

Enveloped Virus Enveloped Virus (HIV)(HIV)

6767


lipid envelope: proteins span the envelope, line its inner surface, spike out above it

viral RNA

reverse transcriptase

viral coat (proteins)

100-120 nm diameter

6868

Body plans of viruses

Viral Body PlansViral Body Plans

6969

7070

7171

VirusesViruses

7272

VirusesViruses

7373

VirusesViruses

7474

VirusesViruses

7575

Viral Multiplication - Basic Viral Multiplication - Basic StepsSteps

Attach to host cellAttach to host cell

Enter host (virus or just genetic material) Enter host (virus or just genetic material)

Direct host to make viral genetic material Direct host to make viral genetic material

and proteinand protein

Assemble viral nucleic acids and proteins Assemble viral nucleic acids and proteins

Release new viral particles Release new viral particles

7676

Bacteriophage multiplication cycles

Viral ReplicationViral Replication

7777

a Virus particle injects genetic material into a suitable host cell after binding to its wall.

e Lysis of host cell is induced; infectious particles escape.

d The coats get tail fibers, other parts.

c Viral proteins are assembled into coats around viral DNA.

b Viral DNA directs host cell to make viral proteins and replicate viral DNA.

LyticPathway

a-1 Viral DNA is integrated into the host’s chromosome.

a-4 Viral DNA is excised from the chromosome.

a-2 Before prokaryotic fission, the bacterial chromosome with the integrated viral DNA is replicated.

a-3 After cell division, each daughter cell will have recombinant DNA.

Lysogenic

Pathway

Fig. 21-15, p.344

Lytic Lytic PathwaPathwayy

7878

Lytic PathwayLytic Pathway

7979

Lytic Lytic PathwayPathway

Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm.

Viral DNA directs host machinery to produce viral proteins and viral DNA.

Viral protein molecules are assembled into coats; DNA is packaged inside.

Tail fibers and other parts are added to coats.

Lysis of host cell is induced; infectious particles escape.

8080

Lytic pathway

Lytic PathwayLytic Pathway

8181

Lysogenic Lysogenic PathwayPathway

Viral DNA usually becomes integrated into the bacterial chromosome.

Prior to prokaryotic fission, the chromosome and integrated viral DNA are replicated.

After binary fission, each daughter cell will have recombinant DNA.

Viral DNA is excised from chromosome and cell enters lytic pathway.

8282

Lysogenic pathway

Lysogenic PathwayLysogenic Pathway

8383

ReplicatioReplication of ann of an

EnvelopedEnvelopedVirusVirus

viral DNA some proteins for viral coat

Replicationof viral DNA

DNA virus particle

plasma membrane of host cell

nuclear envelope

other proteins for viral envelope

Translation

Transcriptionof viral DNA

8484

Replication Replication of anof an

EnvelopedEnvelopedVirusVirus

8585

Enveloped DNA virus replication

Replication of an Enveloped Replication of an Enveloped VirusVirus

8686

Nature of DiseaseNature of Disease

Contagious disease pathogens Contagious disease pathogens must directly contact a new hostmust directly contact a new host

Epidemic Epidemic Pandemic (AIDS)Pandemic (AIDS) Sporadic Sporadic Endemic Endemic

8787

Evolution and DiseaseEvolution and Disease

Host and pathogen are coevolvingHost and pathogen are coevolving If a pathogen kills too quickly, it If a pathogen kills too quickly, it

might disappear along with the might disappear along with the individual host individual host

Most dangerous if pathogen Most dangerous if pathogen Is overwhelming in numbersIs overwhelming in numbers Is in a novel hostIs in a novel host Is a mutant strain Is a mutant strain

8888

Mycobacterium

tuberculosis

8989

SARS virus

9090

9191

New ThreatsNew Threats

Emerging PathogensEmerging Pathogens EbolaEbola virus virus Monkeypox virusMonkeypox virus SARS virusSARS virus

Drug-resistant strainsDrug-resistant strains Food poisoningFood poisoning

E. coliE. coli SalmonellaSalmonella

9292

ViroidsViroids

Smaller than virusesSmaller than viruses

Strands or circles of RNAStrands or circles of RNA

No protein-coding genesNo protein-coding genes

No protein coatNo protein coat

Cause many plant diseases Cause many plant diseases

9393

PrionsPrions

Small proteinsSmall proteins Linked to human diseasesLinked to human diseases

KuruKuru Creutzfeldt-Jakob disease (CJD)Creutzfeldt-Jakob disease (CJD)

Animal diseasesAnimal diseases Scrapie in sheepScrapie in sheep Bovine spongiform Bovine spongiform

encephalopathy (mad cow encephalopathy (mad cow disease)disease)

9494

9595

9696

9797

9898

9999

100100

Documents

Prokaryotes and Viruses