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The World of Microbes:The World of Microbes:Viruses & BacteriaViruses & Bacteria
AP BiologyAP Biology
Chapter 23Chapter 23
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Microbes are…Microbes are…
VirusesViruses BacteriaBacteria
Protists Protists
MicrobiologyMicrobiology is the study of is the study of microbes!microbes!
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Small is Relative!Small is Relative!
11µµmm
Eukaryotic CellsEukaryotic Cells(10-100 (10-100 µµm)m)
Prokaryotic CellsProkaryotic Cells(0.2-10 (0.2-10 µµm)m)
StaphylococcusStaphylococcus
CyanobacteriumCyanobacterium
Escheria coliEscheria coli
VirusesViruses(0.05-0.2 (0.05-0.2 µµm)m)
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VirusesViruses
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VirusesViruses• DNA or RNA surrounded by a protein coatDNA or RNA surrounded by a protein coat• Parasitic - require a host cell (like cells of your Parasitic - require a host cell (like cells of your
body) to replicatebody) to replicate• Infect all kinds of organisms:Infect all kinds of organisms:
BacteriaBacteria Plant cellsPlant cells Animal cellsAnimal cells
• Some viruses only affect certain parts of their Some viruses only affect certain parts of their hosts hosts ex. Rabies affects nervous systemex. Rabies affects nervous system
VirusesViruses
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Are Viruses Alive?Are Viruses Alive?
Viruses are not regarded as living Viruses are not regarded as living organisms; lack some attributes of life.organisms; lack some attributes of life.
• Are infectious particles, Are infectious particles, incapableincapable of of replicating independently.replicating independently.
• Lack cellular organization and Lack cellular organization and metabolism.metabolism.
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VirusesViruses
ReplicationReplication• Viruses reproduce only inside living Viruses reproduce only inside living
cells.cells.• Viruses replicate by infecting Viruses replicate by infecting
susceptible cells and using the cell susceptible cells and using the cell to make more viruses.to make more viruses.
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VirusesViruses
Various illnesses:Various illnesses: flu, AIDS, common coldflu, AIDS, common cold
Some antiviral medicinesSome antiviral medicines Evolve very, very, rapidlyEvolve very, very, rapidly
Makes effective treatment difficultMakes effective treatment difficult Each virus has a host rangeEach virus has a host range
A limited number of host cells that A limited number of host cells that it can infectit can infect
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Virus ShapeVirus Shape
Viral shape is determined by the nature of Viral shape is determined by the nature of the virus’s protein coat. the virus’s protein coat.
Viruses such as the rabies and herpes Viruses such as the rabies and herpes viruses are surrounded by an extra viruses are surrounded by an extra envelope derived from membranes of the envelope derived from membranes of the host cell.host cell.
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Viruses Come in Many ShapesViruses Come in Many Shapes
RabiesRabiesRabiesRabies
MeaslesMeaslesMeaslesMeasles
BacteriophageBacteriophageBacteriophageBacteriophage
HerpesHerpesHerpesHerpes
TobaccoTobaccoMosaicMosaic
TobaccoTobaccoMosaicMosaic
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Viruses infect bacteriaViruses infect bacteria
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BacteriophagesBacteriophages
Viruses called bacteriophagesViruses called bacteriophages• Can infect and set in motion a genetic Can infect and set in motion a genetic
takeover of bacteria, such as takeover of bacteria, such as Escherichia coliEscherichia coli
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Bacteriophages Infect BacteriaBacteriophages Infect Bacteria
BacteriumBacterium
Newly formingNewly formingbacteriophagesbacteriophages
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In this electron micrograph, In this electron micrograph, bacteriophages are seen attacking a bacteriophages are seen attacking a bacterium. bacterium.
They have injected their genetic material They have injected their genetic material inside, leaving their protein coats clinging inside, leaving their protein coats clinging to the bacterial cell wall. to the bacterial cell wall.
The black objects inside the bacterium are The black objects inside the bacterium are newly forming viruses.newly forming viruses.
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Viral Structure -Viral Structure -EnvelopeEnvelope
(lipid bilayer)(lipid bilayer)EnvelopeEnvelope
(lipid bilayer)(lipid bilayer)
ProteinProteinCoatCoat
ProteinProteinCoatCoat
CoreCoreProteinsProteins
CoreCoreProteinsProteins
ReverseReverseTranscriptaseTranscriptase
ReverseReverseTranscriptaseTranscriptase
Genetic MaterialGenetic Material2 RNA molecules2 RNA moleculesGenetic MaterialGenetic Material2 RNA molecules2 RNA molecules
ReceptorReceptorReceptorReceptor
HIVHIVHIVHIV
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Cross section of the virus that Cross section of the virus that causes AIDScauses AIDS
Inside is genetic material surrounded by a Inside is genetic material surrounded by a protein coat and molecules of reverse protein coat and molecules of reverse transcriptase, an enzyme that catalyzes the transcriptase, an enzyme that catalyzes the transcription of DNA from the viral RNA template transcription of DNA from the viral RNA template after the virus enters the host cell. after the virus enters the host cell.
HIV is among those that also have an outer HIV is among those that also have an outer envelope that is formed from the host cell’s envelope that is formed from the host cell’s plasma membrane. Spikes made of glycoprotein plasma membrane. Spikes made of glycoprotein (protein and carbohydrate) project from the (protein and carbohydrate) project from the envelope and help the virus attach to its host envelope and help the virus attach to its host cell. cell.
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Herpes VirusHerpes Virus
Herpes VirusesHerpes Viruses
EnvelopeEnvelope(lipid bilayer)(lipid bilayer)
EnvelopeEnvelope(lipid bilayer)(lipid bilayer)
ProteinProteinCoatCoat
ProteinProteinCoatCoat
Viral DNA inViral DNA inprotein coatprotein coatViral DNA inViral DNA inprotein coatprotein coat
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How Viruses Replicate: Herpes How Viruses Replicate: Herpes
(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
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How Viruses Replicate: HerpesHow Viruses Replicate: Herpes
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
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Herpes VirusHerpes Virus Viruses such as the herpes virus can remain Viruses such as the herpes virus can remain
hidden in the cell for a long time without hidden in the cell for a long time without reproducing.reproducing.• Ex. Herpes virus that causes cold soresEx. Herpes virus that causes cold sores
No symptoms appear until something causes the No symptoms appear until something causes the virus to be active, virus to be active, • such as a fever or sunburn.such as a fever or sunburn.
As long as the virus does not reproduce, there As long as the virus does not reproduce, there are no symptoms.are no symptoms.
When the virus reproduces again, the cold sores When the virus reproduces again, the cold sores reappear.reappear.
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VirusesViruses Diseases caused by viruses are hard to Diseases caused by viruses are hard to
treat or cure.treat or cure. There are no known drugs to destroy There are no known drugs to destroy
viruses, although some may be effective in viruses, although some may be effective in temporarily treating them.temporarily treating them.
The white blood cells of the Immune The white blood cells of the Immune System may surround a destroy a virus.System may surround a destroy a virus.
Antibodies may help destroy viruses.Antibodies may help destroy viruses.• Antibodies only act on one specific kind of Antibodies only act on one specific kind of
virus.virus.
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VirusesViruses VaccinesVaccines
• Harmless substances made from weakened Harmless substances made from weakened or dead virusesor dead viruses
• Stimulate the immune system to create Stimulate the immune system to create defenses (antibodies) against the actual defenses (antibodies) against the actual pathogenpathogen
• Can prevent certain viral illnessesCan prevent certain viral illnesses Examples: chicken pox, flu, measles, Examples: chicken pox, flu, measles,
mumps, rubella, hepatitismumps, rubella, hepatitis
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Prokaryotes:Prokaryotes:
Archaea & BacteriaArchaea & Bacteria
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The Tree of LifeThe Tree of Life
All living things All living things classified in three classified in three domains:domains:
• BacteriaBacteria• ArchaeaArchaea• EukaryaEukarya
All living things All living things classified in three classified in three domains:domains:
• BacteriaBacteria• ArchaeaArchaea• EukaryaEukarya
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Amazing Living ThingsAmazing Living Things Microbes indispensable to life: Microbes indispensable to life: Produce much of Earth’s:Produce much of Earth’s:
OxygenOxygen DecompositionDecomposition Over half of Earth’s biomassOver half of Earth’s biomass
More bacterial cells than human cells in More bacterial cells than human cells in your body!your body!
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ProkaryotesProkaryotes Prokaryotes have:Prokaryotes have:
• Circular DNA, RNA, ribosomes, cytoplasm, Circular DNA, RNA, ribosomes, cytoplasm, plasma membraneplasma membrane
• Most prokaryotes have a cell wall, a capsule Most prokaryotes have a cell wall, a capsule (around the cell wall) and a flagellum (around the cell wall) and a flagellum
Prokaryotes Prokaryotes don’tdon’t have: have:• Organelles such as nucleus, chloroplasts, Organelles such as nucleus, chloroplasts,
mitochondria.mitochondria.
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Generalized ProkaryoteGeneralized Prokaryote
CapsuleCapsule
Cell WallCell WallPlasmaPlasmaMembraneMembrane
CytosolCytosol
Nucleoid DNANucleoid DNA
FlagellumFlagellum
Plasmid DNAPlasmid DNA
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Prokaryotic DNAProkaryotic DNA
The area that contains the genetic material The area that contains the genetic material is referred to as the is referred to as the nucleoidnucleoid. .
The genes are usually in one continuous The genes are usually in one continuous circular loop of DNA.circular loop of DNA.
There may be other small circles of DNA There may be other small circles of DNA outside the nulceoid called outside the nulceoid called plasmidsplasmids..
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Bacteria/ArchaeaBacteria/Archaea Habitats (name a place, and they live Habitats (name a place, and they live
there!)there!)• They are specialistsThey are specialists
human skin, mouth, respiratory tract, large human skin, mouth, respiratory tract, large intestine, urogenital tract, etc.intestine, urogenital tract, etc.
salty Dead Seasalty Dead Sea extreme pHextreme pH archea in deep sea vents: 90-106archea in deep sea vents: 90-106o o CC
• Aerobes and anaerobesAerobes and anaerobes
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Some Prokaryotes Thrive in Extreme Some Prokaryotes Thrive in Extreme ConditionsConditions
Cyanobacteria in Yellowstone Cyanobacteria in Yellowstone Hot SpringsHot Springs
Cyanobacteria in Yellowstone Cyanobacteria in Yellowstone Hot SpringsHot Springs
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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 stomachsstomachs
Halophiles - survive concentrated salt Halophiles - survive concentrated salt environmentenvironment
Thermoacidophiles - thrive in hot, acidic Thermoacidophiles - thrive in hot, acidic environmentenvironment
Generally in EXTREME environmentsGenerally in EXTREME environments
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BacteriaBacteria
Evolve RapidlyEvolve Rapidly Most of the time are asexualMost of the time are asexual
Classified by shape, locomotion, pigments, Classified by shape, locomotion, pigments, nutrients, nutrients, coloniescolonies
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BacteriaBacteria
Shape:Shape:• Cocci - roundCocci - round
• Bacilli - rodBacilli - rod
• Spirilla - spiralsSpirilla - spirals
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Three Common Bacterial ShapesThree Common Bacterial Shapes
(a)(a)(a)(a) (b)(b)(b)(b)
(c)(c)(c)(c)
coccicoccicoccicocci
spirillusspirillusspirillusspirillus
bacillusbacillusbacillusbacillus
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The Prokaryote FlagellumThe Prokaryote Flagellum
BacteriumBacteriumBacteriumBacterium
FlagellaFlagellaFlagellaFlagella
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BacteriaBacteria
ReproductionReproduction
Reproduction is asexual, by simple Reproduction is asexual, by simple splitting (binary fission)splitting (binary fission)
Daughter cells are genetic clones of Daughter cells are genetic clones of the parent cellthe parent cell
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Binary FissionBinary Fission
DNADNADNADNA
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Bacteria - ReproductionBacteria - Reproduction
Binary fission:Binary fission:
• Very fast, up to once every 20 minutesVery fast, up to once every 20 minutes
• One bacterium-> 10One bacterium-> 102121 in 24 hours. in 24 hours.
ConjugationConjugation: (sexual reproduction): (sexual reproduction)
• Used only occasionally.Used only occasionally.
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Bacteria – Sexual ReproductionBacteria – Sexual Reproduction
Conjugation:Conjugation:• Genetic variation through pili (structures Genetic variation through pili (structures
similar to flagella) and plasmid DNAsimilar to flagella) and plasmid DNA• DNA is exchanged between bacterial DNA is exchanged between bacterial
cellscells• Occurs through a special large, hollow Occurs through a special large, hollow
piluspilus• One bacterium acts as a donor, One bacterium acts as a donor,
transferring DNA to the recipient.transferring DNA to the recipient.
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ConjugationConjugation
Sex PilusSex PilusSex PilusSex Pilus
DonorDonorDonorDonor
RecipientRecipientRecipientRecipient
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Benefits of BacteriaBenefits of Bacteria
Symbiosis (mutualism) Symbiosis (mutualism) • Ruminants’ digestive tractsRuminants’ digestive tracts• Nitrogen fixing in soil, nodules on certain Nitrogen fixing in soil, nodules on certain
legumeslegumes• Bacteria on/in the human body: intestines and Bacteria on/in the human body: intestines and
vitamin K and B12vitamin K and B12 Biodegradation - oilBiodegradation - oil Food production - cheese, yogurt, Food production - cheese, yogurt,
sauerkrautsauerkraut DecomposersDecomposers
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Our Relationship With BacteriaOur Relationship With Bacteria
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Bacterial PathogensBacterial Pathogens Some cause disease = Some cause disease = pathogenicpathogenic In humans:In humans:
• Strep throatStrep throat• Toxins - tetanus, botulismToxins - tetanus, botulism• Pneumonia Pneumonia • "Flesh-eating" bacteria"Flesh-eating" bacteria• PlaguePlague• TuberculosisTuberculosis• Cholera Cholera • Lyme diseaseLyme disease
ANTIBIOTICS= anti bacterial!!!ANTIBIOTICS= anti bacterial!!!
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The Causes of Tooth DecayThe Causes of Tooth Decay
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Transmission of Bacterial Transmission of Bacterial PathogensPathogens
AirborneAirborne Water Water FoodFood Direct (skin contact, blood, and other Direct (skin contact, blood, and other
body fluids)body fluids) Insect vectors and other hosts such Insect vectors and other hosts such
as deer tick (Lyme) or mosquito.as deer tick (Lyme) or mosquito.
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Germ Theory of DiseaseGerm Theory of Disease
Theory that microorganisms are the Theory that microorganisms are the cause of disease. cause of disease.
1859 – Louis Pasteur 1859 – Louis Pasteur • Credited with the idea that human Credited with the idea that human
diseases were caused by bacteria and diseases were caused by bacteria and viruses (germ theory)viruses (germ theory)
• Very important discovery in the field of Very important discovery in the field of medicinemedicine
• Also created vaccinations to prevent Also created vaccinations to prevent diseasedisease
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Infectious DiseasesInfectious Diseases
Average age of death, in first world Average age of death, in first world countries, jumped 30+ years in last countries, jumped 30+ years in last century due to antibiotics, and enhanced century due to antibiotics, and enhanced hygiene and nutrition.hygiene and nutrition.
Antibiotic-resistant infections on the rise in Antibiotic-resistant infections on the rise in hospitals in the U.S.hospitals in the U.S.• This is due to bacterial evolution in response This is due to bacterial evolution in response
to widespread use of antibiotics!to widespread use of antibiotics!