Exam 1 Study Guide (Lecture 1 -5) Flashcards
Define microbes
living things ordinarily too small to be seen without magnification, there are cellular and noncellular microorganisms.
Acellular microorganisms: Viruses and prions
Cellular microorganisms: Bacteria, Archaea, Fungi, Plants, Protozoa, and Helminths
Define cells
An autonomous self-replicating unit that may exist as a functional independent unit of life or a sub-unit in a multi-cellular organism.
Define organisms
A living thing that has an organized structure, can react to stimuli, reproduce, grow, adapt, and maintain homeostasis.
Why should we study microbes?
- To advance human life and shape civilizations
- To understand them to treat infectious diseases
Benefits of microbes?
-Gut health
-Ocean microbes produce majority of earth’s oxygen
-Can study them to create antibiotics and medications
-Wine/beer
Who is Antonie van Leeuwenhoek?
Father of Protozoology and Bacteriology. Observed the first microbe.
Self-taught scientist inspired by Hook.
Robert Hooke and the discovery of cells
In 1665 Hooke discover the first cell with a primitive microscope he designed
What is cell theory?
All living things are composed of cells and comes from cells
What is spontaneous generation?
Living organisms arise from nonliving matter due to “vital force”
What is biogenesis?
Living organisms arise from preexisting life.
“beginning with life”
What is abiogenesis?
Embraced spontaneous generation
“beginning in absence of life
What were the four questions of the Golden Age of Microbiology?
- What causes fermentation?
- Is spontaneous generation of microbial life possible?
- What causes diseases?
- How can we prevent diseases?
What is the scientific method?
Observation (identify a problem)
-> hypothesis (ask questions to develop a prediction)
-> experiment (test the hypothesis)
-> data collection/ analysis (record and analyze experiment results)
-> reject/accept/modify hypothesis (draw conclusions based on data and hypothesis)
->theory or law
What is Pasteur’s experiments? (set up, purpose, results, conclusions, critics)
Set up: Used a swan neck flask filled with beef and plant extract, and boiled it
Purpose: To prove whether Biogenesis or Spontaneous Generation was accurated
Results: Dust formed at the neck of the open swan flask and no bacteria grew on the liquid, so he modified the experiment to reject Spontaneous Generation, and swirled the liquid with the dust to later see microbes growing in the water.
Conclusions: Proved Biogenesis, that microbes are present in the air, and the living organisms arise from preexisting life.
Critics:
What are Koch’s four postulates?
- The suspected pathogenic organism should be present in all cases of the disease and absent from health animals
- The suspected organism should be grown in pure culture.
- Cells from a pure culture of the suspected organism should cause disease in a healthy animal.
- The organism should be re-insulated and shown to be the same as the original.
How can microbes be classified?
Microbes can be classified as prokaryotic or eukaryotic.
Prokayrotic microbes are Eubacteria and Archaea that have no nucleus.
Eukaryotic microbes have a nucleus and are classified as Protist, Plant, Fungi, and Animal (Helminths).
What are the main characteristics of Prokaryotes?
- No nucleus
- 1-cell organisms/ uni-cellular
- Rigid walls that confer cell shape
- Cytoplasmic membrane is comprised from a phospholipid bilayer
- Bacteria and Archaea
- Chromosome is found in an area of the cytoplasm called the nucleoids
What are the main characteristics of helminths?
- Eukaryote (has nucleus)
- Multicellular animals (macro-organisms) 3. Parasitic flat worms and round worms
- Microscopic stages in life cycles
What are the main characteristics of fungi?
- Eukaryotic
- Membrane-bound nucleus
- Multi-cellular or unicellular
- Obtain food from other organisms (decomposers)
- Possess cell walls
- Composed of molds (multicellular, have hyphae, reproduce sexually and asexual spores)
- Composed of yeasts (unicellular, reproduce asexually by budding, some produce sexual spores)
What are the main characteristics of protozoa?
- Single-celled Eukaryote
- Most free living (need water to survive)
- Capable of locomotion by: pseudopodia, cilia, and flagella
- Most reproduce asexually
What are the main characteristics of algae?
- Unicellular or multicellular eukaryote
- Photosynthetic
- Simple reproductive structures
- Categorized based on: pigmentation, storage of products, and composition of cell wall
What are the main characteristics of viruses?
- Acellular (not cells)
- Consists of DNA or RNA core (never both)
- Has a protein coat
- Only replicates inside a living host.
- Bacteriophages can be rises that attack bacteria
What are the five I’s in order?
- Inoculation
- Incubation
- Isolation
- Inspection
- Identification
What is the process of inoculation?
When a sample is placed into a container of growth medium. Medium can be solid or liquid or a live animal such as a a chicken embryo.
- culture: to grow microorganisms
-medium: nutrients for the growth of microbes
-inoculum: a small sample of microbes
-inoculation: the introduction of an inoculum into media to culture/ grow
-clinical specimens are obtained from body fluids, discharges, anatomical sites, or diseased tissue
What is the process of incubation?
Creates the proper growth conditions with respect to temperature and gas requirements.
-atmospheric gases such as oxygen or carbon dioxide may be required for the growth of certain microbes
-during the incubation period, the microbe multiplies and produces growth that is observable macroscopically
What is the process of isolation?
Re-inoculate to separate species.
Once the cultures have grown, they may need to be re-inoculated (and incubated) in such a way that separate species are obtained.
What is the process of inspection?
The colonies on agar or the broth cultures are observed macroscopically and microscopically, possibly with the aid of staining.
New plate/tube, observe colonies
What is the process of identification?
Identity of isolated microbe is usually determined on a species level.
Genus and species
Discuss three physical states of media and when each is used?
- Solid - plate, slant, agar deep
- Semisolid - “low density jello”
- Liquid - for broth
Compare and contrast selective and differential media and give an example of each.
Selective Media
-Contains one or more agents that inhibit the growth of a certain microbe or microbes:
-important in the primary isolation of a specific type of microorganism from a sample containing dozens of different species
-Speed up isolation by suppressing unwanted background organisms and favoring the growth of the desired ones
Differential Media
-Allow multiple types of organisms to grow but display visible differences in how they grow:
-Variations in colony size or color
-Media color changes
-Production of gas bubbles
-Variations often come from chemicals in the media with which microbes react
Compare and contrast selective and differential media and give an example of each.
Selective Media contains on or more agents that inhibit the growth of a certain microbe or microbes.
Differential Media allow multiple types of organisms to grow but display visible differences in how they grow. While selective media focuses on primary isolation of a specific type of organisms by suppressing unwanted background organisms, differential media can also place focus on specific type of bacteria by focusing on displaying visible differences in how they grow. It is a form of isolation that allows the bacteria to standout apart from other variations.
Example: MacConkey agar suppresses the growth of some organisms while producing a visual distinction between the ones that do grow.
Dyes are used as differential agents because many are pH indicators that changed color in response to the production of an acid or a base.
Provide brief definitions for defined media and complex media
Defined Media:
- composition is precisely chemically defined
-Contains pure organic and inorganic compounds that vary little from one source to another
-Molecular content specified by means of an exact formula
Complex Media:
-One or more components is not chemically defined
-Contains extracts of animals, plants, or yeasts
-Blood, serum, meat extracts or infusions, milk, yeast extract, soybean digests, and peptone
What is the use of agar in culture media?
A complex polysaccharide that is solid at room temperature and liquefies at 100 C, it is flexible and moldable, and it is not a digestible nutrient for most microorganisms
Describe the 3 methods to isolate bacteria on plates
Streak Method: on solid media, use a loop to dip into bacteria for a sample and do a streak in one corner of the plate, sterilize loop in fire, touch the first bacteria line, and streak the second line, sterilize loop again, and repeat these steps until fourth line is created.
Pour Method: On liquified solid medium, use loop to get bacteria sample and put in water or broth, get concentration from this then dilute it into the second tube, do previous steps into third tube, pour into a plate (for each solution in tubes), use solid agar that you liquefy, pour agar liquid into plates, media forms for bacteria to grow.
Spread Method: On solid media, add an amount of bacteria in liquid onto plate, use a “hockey stick” and anchor in center of plate, turn plate 360 degrees a couple of times, incubate, and find colonies.
How do you calculate the total magnification when viewing specimens under specific microscope lenses?
total magnification is
objective lens x ocular lens
ex:
objective lens (10x) x 10x low power objective= 100x magnification
10x x 40x high dry objective= 400x magnification
10x x 100 oil immersion objective= 1000x magnification
Explain the pathway of light through the compound light microscope
The light begins from the light sources, goes through the condenser, then shine onto the specimen/sample located on top of the stage, light then travels through the objective lens giving a real image, the real image will then be projected through the tube through the ocular lens and perceived by the human eye or onto a camera.
light source -> condenser -> sample -> objective lens -> tube -> ocular lens -> eye or camera
Which parts of the microscope allow adjustment of light through the specimen?
Iris diaphragm and Condenser
List and describe three elements of good microscopy?
- Resolution: aka resolving power is the capacity of an optical system to distinguish two adjacent objects or points from one another.
- Magnification: occurs in two phases through the real image formed by the objective lens and the virtual image formed when the image is projected up through the microscope body to the plane of the eyepiece, the ocular lens forms the second image
- Contrast: the degree of bending that light undergoes as it passes from one medium to another; refractive index; the higher the difference in the refractive indexes (the more bending of light) the sharper the contrast registered
Differentiate between the principles of light microscopy and the principles of electron microscopy
Light Microscopy: forms image when light is transmitted through the specimen; the specimen being denser and more opaque than its surroundings absorb some of this light, and the rest of the light is transmitted directly up through the ocular lens
Electron Microscopy: transmits electrons, 3D view, electrons deflect and electron pattern is displayed on screen
Give examples of simple, differential, and special stains
Simple Stains: Crystal violet stain
Differential Stains: Gram Stain
Special Stains: Capsular Stain
What are the basic characteristics of prokaryotes?
-Single celled organisms
-No nucleus
-Have a cell wall
-Lack complex membrane bound organelles
-Have ribosomes
What are the habitats of prokaryotes?
Diverse habitats and can live in extreme conditions:
- Antarctic glaciers, thermal hot springs
-Colons of animals
-Distilled water
-Disinfectant solutions, basalt rocks
Known estimated number of prokaryotic species?
200 species
What are the main characteristics of bacteria vs. archaea?
Archaea
-membrane lipids with branched hydrocarbons
-Methionine is the initiator amino acid for protein synthesis
-Lack peptidoglycan in the cell wall
-Growth not inhibited by streptomycin and chloramphenicol
-Histones are associated with DNA
-Contains several types of RNA polymerase
Bacteria and Archaea:
-Chromosomes are circular
-Lacks nuclear envelopes
-Lacks membrane bound organelles
What are the prokaryotic external cell structures?
Prokaryotic external appendages:
1. Flagella
2. Fimbriae
3. Pili
What is the function of the flagella?
This external prokaryotic appendage facilitates movement (motility) and can rotate 360 degrees. It can tumble by clockwise rotation and it can run by counterclockwise rotation.
It has 4 types:
1. Monotrichous (one pole)
2. Amphitrichous (both poles)
3. Lophotrichou (multiple from one pole)
4. Petrichous (all over)
What is the function of the fimbriae?
This external prokaryotic appendage has non motile extensions, and can adhere to other bacteria, hosts, and substances. Required for formation of biofilms (dental plaque).
What is the function of the pili?
This external prokaryotic appendage has non motile extensions. Join 2 bacteria and mediate the DNA transfer between cells (conjugation)
What is the function of the prokaryotic cell wall?
Composed of peptidoglycan (polysaccharides) it provides structures and shape from osmotic forces, helps cells attach to other cells, helps eludes antimicrobial drugs
What is the function of the prokaryotic cell membrane?
The phospholipid bilayer (fluid mosaic) controls the passage of substances in and out of the cell
What is the function of the prokaryotic ribosomes?
This is the site for protein synthesis floating in the cytoplasm.
What is the function of the prokaryotic nuceloid?
Area containing DNA
What are the function of plasmids in prokaryotes?
Extra chromosomal DNA capable of replicating independently
What are the methods or reproduction for prokaryotes?
Binary Fission: a sexual reproduction by a separation of the body into new bodies. The organism duplicates its genetic material and then divides into two new parts.
Snapping Division: two daughter cells remain attached by the outer layer of the cell wall. DNA replication and binary fission has already occurred.
Reproductive Structures: Nucleoid replicates, new nucleoid moves into the bud, resulting in budding and new cell.
What are the shapes of prokaryotes?
Coccus - round
Coccobacillus - round and long
Bacillus - rod
Vibrio - long and thicker on one end
Spirillum and Spirochete - spiral
Pleomorphic - irregular shapes
What are the prokaryotic arrangements?
Bacilli arrangement (rods)
Cocci arrangement (round)
What are the formation, positions, and purpose of endospores?
Endospore Formation: vegetative cycle then sporulation cycle
Endospore Positions: central spore, subterminal spore, terminal spore, and terminal spore w/ swollen sporangium
Endospore Purpose: Help defense against unfavorable conditions, such as heat radiation and lethal chemicals. They are viable for tens to thousands of years; stable resting stages. ex: Anthrax
What are the types of archaea and major characteristics?
The two types of archaea:
-Extremophiles:
-Thermophiles - heat tolerant
- Halophiles - salt tolerant
-Methanogens: carbon dioxide to methane
377 known species
No known association with human diseases
What are lipoteichoic acids?
Anchors peptidoglycan to cell membrane in prokaryotes
What are the four eukaryotic kingdoms?
- Kingdom Protista
- Kingdom Plantae
- Kingdom Fungi
- Kingdom Animalia
What are the eukaryotic kingdom protista characteristics and classifications?
Characteristics:
- Most are unicellular (except kelp) can aggregate
-Aquatic or moist areas
-Some with cell wall
-Some with photosynthetic ability
-Most are motile (flagella, cilia, pseudopods)
-Autotrophic or heterotrophic
-Reproduce mostly asexually
-Some are parasites and cause diseases in humans
-Foundation of food chain
Classifications:
-Based on their method of motility: Sarcodina (pseudopods), Ciliophora (cilia), Mastigophora (flagella), and Sporozoa (gliding motility)
Examples: Algae (photosynthetic protists), Protozoa (Predator or parasitic) and Slime Molds (saprophytic protists)
What are the eukaryotic kingdom plantae characteristics and classifications?
Characteristics:
-Multicellular
-Cell wall, vacuole
-Photosynthetic ability, chlorophyll
-Mostly non-motile (can’t move)
-Autotrophic (can generate their own nutrients from photosynthetic ability)
-Reproduce sexually (flowering plants) or asexually
-Some contain substances that can be poisonous to humans
Classifications:
-Nonvascular Bryophytes, Vascular Seedless Plants and Vascular Seed Plants
Examples:
Ferns, mosses, flowers
What are the eukaryotic kingdom fungi characteristics and classifications?
Characteristics:
-Most are multicellular
-Moist areas
-Cell wall composed of chitin
-Nonmotile
-Chemoheterotrophic, no chlorophyll, instead they absorb nutrients via adsorption
-Reproduce asexually or sexually
-Nuclear envelope not dissolved during cell division
-30% cause diseases in plants and animals (food poisoning, parasitic infection, allergies in humans)
Classifications:
Basidiomycota, Ascomycota and Zygomycota
Examples:
Bread molds, Sac Fungi , Club Fungi: Spoil fruits, pickles, jams, jellies
What are the eukaryotic kingdom animalia characteristics and classifications?
Characteristics:
-Multicellular
-No cell wall (glycocalyx)
-No photosynthetic ability
-Mostly motile
-Heterotrophic (feed on others)
-Reproduce sexually or asexually
-Small numbers can cause health issues in humans
Classifications:
Platyhelminthes and Nematoda
Examples:
Flatworms, roundworms
What are the eukaryotic external cell structures?
External structure:
-Appendages: Flagella and Cilia
-Glycocalyx
-Slimes
What is the function of the eukaryotic flagella?
The external appendage, flagella, is:
-present in protists, animal cells, some plant sex cells/plant sperm
-Generally found at one pole of cell
-Do not rotate, but undulate rhythmically
What is the function of the eukaryotic cilia?
The external appendage, cilia, is:
-Present in protists and animal cells
-Coordinated beating propels cells through their environment
-Also used to move substances past the surface of the cell
What is the function of the eukaryotic glycocalcyx?
The external cell structure, glycocalyx is:
-present in animal cells only, not in all eukaryotic cells
-Helps animal cells adhere to each other
-Strengthens cell surface
-Provides protection against dehydration
-Functions in cell-to-cell recognition and communication
What is the function of the eukaryotic slimes?
need to work on this
What makes up the boundaries of the eukaryotic cell?
The cell wall and cytoplasmic membrane.
What is the function of the eukaryotic cell wall?
Eukaryotic cell wall
- not in animal cells
-all have cellulose in fungi, algae, and plants (no glycocalyx)
What is the function of the eukaryotic cytoplasmic membrane?
Eukaryotic cytoplasmic membrane:
-Fluid mosaic of phospholipids and proteins
-Contains steroid lipids to help maintain fluidity
-Controls movement into and out of cell (use diffusion, facilitated diffusion, osmosis, and active transport
-Vesicular transport (endocytosis and exocytosis
What is this type of vesicular transport in eukaryotic cells that import substances?
Endocytosis is the process.
What is this type of vesicular transport in eukaryotic cells that exports substances?
Exocytosis
What are the internal eukaryotic cell structures?
- Cytoplasm
- Nucleus
- Organelles
- Ribosomes
- Cytoskeleton
Where is the site of DNA replication and transcription in the eukaryotic cell? (DNA ->mRNA)
The nucleus
What is the phospholipid bilayer that contains nuclear pores in a eukaryotic cell?
Nuclear envelope
Where is the site of ribosomal RNA synthesis in the eukaryotic cell?
Nucleolus
What is the function of the chromosomes in a eukaryotic cell?
need to find answer
What is the liquid portion in a eukaryotic cell?
Nucleoplasm
What are all the organelles in a eukaryotic cell?
- Endoplasmic Reticulum - Ribosomes
- Golgi Apparatus - Lysosomes
- Mitochondria
- Chloroplasts
What is the function of the endoplasmic reticulum - ribosomes do in the eukaryotic cell?
- Biosynthetic factory
- Protein modification
- Transport
What is the function of the Gogli Apparatus in the eukaryotic cell?
- Shipping center
- Modifies products of the endoplasmic reticulum
- Manufactures certain macromolecules
- Receives, sorts, and packages materials into transport vesicles to export and traffic within cell
What is the function of the mitochondria in in the eukaryotic cell?
- Powerhouse of the cell
- Produce energy, ATP
- Carry out reactions where oxygen is used to break down food
- Aerobic respiration
What is the function of the chloroplasts in the eukaryotic cell?
- Used by algae and plants for photosynthesis
- Contain 780S ribosomes and circular DNA
Where is the site for protein synthesis in eukaryotic cells?
Ribosomes
What is the function of the ribosomes in a eukaryotic cell?
- sites for protein synthesis
What is the function of the cytoskeleton in a eukaryotic cell?
- provides basic shape for the cell
- anchor organelles
- cytoplasmic streaming and movement of organelles
- Cell contraction
- Movement during endocytosis / exocytosis
- Amoeboid action (pseudopodia)
What are all the type of reproductive mechanisms in eukaryotes?
- Mitosis
- Meiosis
- Binary Fission
- Budding
- Schizogony
- Sporulation
- Conjugation
What is the endosymbiotic theory?
This is the theory that eukaryotes formed from phagocytosis of small aerobic prokaryotes.
- Lost ability to exist independent
- Retained portion of DNA, ribosomes, and cytoplasmic membranes
- Larger cell became dependent on for aerobic ATP production
- Aerobic prokaryotes evolved into mitochondria
- Photosynthetic bacteria evolved into chloroplasts
What is mitosis?
The division into 2 equal nuclei
1 diploid cell to 2 diploid cells
Only in somatic cells (body cells)
What is meiosis?
Chromatids are separated, genome is halved at the end of the process
1 diploid cell to 4 halpoud cells
Only in sex cells (pre-sperm, pre-egg cells)
What is binary fission?
Asexual process
Occurs in Amoeba and Paramecium
Nuclear and cytoplasmic division occur
What is budding?`
Asexual
Creating clones
Nuclear and cytoplasmic
Happens in unicellular (yeast) or multicellular (hydra, corals) eukaryotes
What is schizogony?
Asexual
Multiple divisions of nucleus without division of cytoplasm
Reduced cell size
Parasitic protozoa (ex Malaria)
What is conjugation
Sexual
Happens in paramecium and Zygomycota
Nuclear and cytoplasmic division
What are characteristics of the protozoa: archezoa?
No mitochondria
Multiple flagella
Giardia lamblia (small intestine infection)
Trichomona vaginalis (no cyst stage) (STF, irritation, itching)
Chilomastix (nonpathogens, gastrointestinal tract)
What are characteristics of the protozoa: rhizopoda?
Move by pseudopds
Entamoeba (some are animal intestinal parasites)
Acanthamoeba (rare eye, skin, brain infections)
Full grown Amoeba usually divide by binary fission; sometimes they do multiple fission, only occurs once it secretes a cyst wall
What are characteristics of the protozoa: Apciomplexa?
Nonmotile
Intracellular parasites
Complex life cycles
Plasmodium (malaria)
Babesia (Lyme disease)
Cryptosporidium (crypto, diarrhea)
Cyclospora (cyclosporiasis, diarrhea)
What are characteristics of the protozoa: Ciliophora aka Cilates?
Move by cilia
Complex cells
Paramecium
Balantidium coli is the only human parasite (balantidiasis)
What are characteristics of the protozoa: Euglenozoa?
Move by flagella
Photoautotrophs
Euglenoids
Chemoheterotrophs
Naegleria
Flagellated and amoeboid forms, meningoencephalitis
Trypanosoma
Leishmania
What is the protozoan life cycle?
Only two stages:
1. trophozoite (feeding, motile, and replication)
2. Cysts (passed in feces, resistant, infective)
Algae: chlorophyta vs phaeophyta vs rhodophyta vs bacillariophyta
Chlorophyta: Green algae, cellulose cell walls, unicellular or multicellular
Phaeophyta: Brown algae, multicellular, stores carbohydrates
Rhodophyta: Red algae, cellulose cell walls, multicellular, harvester for agar and carrageenan.
Bacillariophyta: Microalgae, pectin and silica cell walls, unicellular, store oils
What type of algae is Green algae, cellulose cell walls, unicellular or multicellular
Chlorophyta
What is brown algae, multicellular, stores carbohydrates ?
Phaeophyta
What is red algae, cellulose cell walls, multicellular, harvester for agar and carrageenan.
Rhodophyta
What is microalgae, pectin and silica cell walls, unicellular, store oils?
Bacillariophyta
What are the characteristics of protists dinoflagellates?
Cellulose in plasma membrane
Unicellular
Chlorophyll a and c, carotene, xanthines
Store starch
Some are symbionts in marine animals
Neurotoxins cause paralytic shellfish poisoning
What are the characteristics of protists Oomycota?
Water molds
Cellulose cell walls
Multicellular
Chemoheterotophic
Produce zoospores
Decomposers and plant parasites
What are the characteristics of protists slime molds?
Cellular slime molds
-Resemble amoebas, ingest bacteria by phagocytosis
-Cells aggregate into stalked fruiting body
-Some cells become spores
Plasmodial slime molds
-Multinucleated large cells
-Cytoplasm separates into stalked sporangia
-Nuclei undergo meiosis and form uninucleate haploid spores
Fungi: zygomycota vs ascomycota vs basidiomycota
Zygomycota: bread mold, conjugation fungi, soil and decaying plant materials, produce sporangiospores.
Ascomycota: Sac fungi, penicillium
Basidiomycota: club fungi, filamentous except yeast, septate
Economic effects of fungi and mycoses
Fungi:
Sacharamyces:
Positive effect: bread, wine, beer; Negative effect: food spoilage
Trichoderma: Positive effect: cellulose used for juices and fabric
Taxomyces: Positive Effect: Taxol production
Mycoses: Affects deep within the body, beneath the skin, affect the hair and skin, localized areas. Opportunistic mycoses caused by normal microbiota or fungo that are harmless.
Helminths: trematodes vs cestodes vs nematodes
Trematodes (flukes): type of flatworm thrive in mammals, birds, amphibians, reptiles and fish.
Cestodes (tapeworm): intestinal worms with complex life cycles involving multiple hosts, transmitted to people
Nematodes (roundworms): small organisms that can live in the human intestinal for a long time. They can be harmful, found in dogs and can be transmitted to people.
Arthropods, vectors for diseases
Animal vectors for disease that carry and transmit microscopic pathogens. Such as insects: lice, fleas and mosquitos or Archnida:mites and ticks.
Lichen: formation, make up, types
A plant like organism that grows on solid surfaces, such as rocks or trees and is made up of fungus and an algae or cyanobacterium.
Eaten by many animals.
They do not have roots, leaves or stems yet they grow on soil rocks and leaves.
Know the brief history of virology
First learned in late 1800s with TMD - tobacco mosaic disease, they found the plant sap was infectious
1935 TMV (tobacco mosaic virus) was isolated and purified
1982 when coiled the term “virus” means poison in latin
How can we identify viral infection on plants or in tissue-cultured cells?
Cytopathic effects
Look at cell’s features
What are three ways to grow viruses?
Viruses must be grown in living cells
In the lab can use a lawn of bacteria and bacteriophages form plaques on them; Bacteriophages are viruses that infect bacteria
Tissue culture techniques were developed
Continuous cell lines may be maintained indefinitely
How are viruses classified (based on viral components)?
Genome composition: RNA or DNA
dsDNA (double stranded)
ssDNA (single stranded)
dsRNA
ssRNA
Look to see presence of envelope
-Is the capsid surrounded by a phospholipid bilayer derived from the hosts plasma membrane?
-Enveloped vs uneveloped?
Capsid: made up of capsomeres (proteins) differentiated by symmetry
-Helical viruses
Capsomeres arranged in a tube, nucleic acid inside
Polyhedral viruses
-Lcosahedral (20 faces, 12 corners)
Complex viruses
-Capsid + tail + tail fibers + pins +faceplate
How are viruses named?
The disease they cause
Poliovirus, mumps virus, measles virus
The river near place of isolation
Ebola virus
Viruses that infect bacteria
Are called bacteriophages
Letters and numbers are used for names
Ex: T4
Be able to distinguish: enveloped vs. unenveloped viruses, different types of capsids.
A viral envelope is the outermost layer of many viruses. It protects the genetic material in their life cycle when traveling between hosts
Non-enveloped viruses are more resistant to extreme pH, heat, dryness, and simple disinfectants.
Examples include norovirus, enterovirus and rhinovirus.
Understand the range of hosts for viruses. What determines this range?
Determined by specific receptors on the host cell surface
Due to specialized receptors on host cells
Viruses have specific hosts
Plant
Animal
Bacteria
Know lytic and lysogenic cycles of bacteriophages.
Lytic cycle:
Phage causes lysis and death of host cell
Lysogenic cycle:
Prophage DNA incorporated in host DNA (temperate changes)
Know the life cycles of different animal viruses. How are they different from the life cycle of bacteriophages?
Differences of Animal Viruses Viral Life Cycle:
Presence of envelope around some viruses
Eukaryotic nature of animal cells
Lack of cell wall in animal cells
Viral Life Cycle of Animal Viruses
Adsorption/ attachment: virus attaches to cell membrane
Chemical attraction
Animal viruses do not have tails or fibers
Have glycoprotein spikes or other attachment molecules that mediate attachment
Penetration: by endocytosis or fusion (viral nucleic acid enters host cell)
Bind to receptors on cytoplasmic membrane
Phagocytosis (type of endocytosis)
Opening of vesicle and uncoating
Uncoating: by viral or host enzymes (release viral nucleic acids from viral capsid into host cell)
Replication/Biosynthesis: Production of nucleic acid and capsid proteins assemble
Assembly: Nucleic acid and capsid proteins assemble (maturation)
Release: By budding (enveloped viruses) or rupture
Know the life cycles of DNA, RNA, and retroviruses. How are they different from each other?
DNA viruses
Assembly in nucleus
RNA viruses
Develop solely in cytoplasm
Number of viruses produced and released depends on
Type of virus
Size of virus
Initial health of host cell
Enveloped viruses cause persistent infections (budding for release)
Naked/ un-enveloped viruses released by exocytosis or may cause lysis and death of host cell
What is the latency of viruses?
Some viruses can remain dormant
May exist for years with no viral activity, signs, or symptoms
Some latent viruses do not become incorporated into host chromosome
When provirus is incorporated into host DNA, condition is permanent; becomes permanent physical part of host’s chromosome
How can oncogenic viruses cause cancer?
Some carry copies of oncogenes (form cancers) as part of their genomes
Some stimulate oncogenes already present in host
Some interfere with tumor repression when they insert into host’s repressor gene
What are the causes of cytopathic effects by viruses?
Host cell DNA, RNA and protein synthesis has been stopped by virus
Fusion of the plasma membranes of many cells (Herpes viruses)
Inclusion bodies in host cytoplasm
Rabies = Negri bodies (viral particles)
Toxic effect of capsid proteins
Mumps virus and influenza virus
Host Chromosomal Disruptions
Herpes Virus
Transformation of cells into malignant (cancerous) cells
What are 3 types of viral infections? Describe.
Acute Viral Infections
Rapid onset, short duration
Influenza
Latent Viral Infections
Virus remains dormant and is later induced into activity
HSV1- cold sores
Varicella-zoster virus - shingles
Chronic/ Persistent Viral Infections
Long duration, generally fatal
HCV - hepatitis C
Measles virus - subacute sclerosing panencephalitis
What methods can be used to identify viral infections?
Cytopathic effects
Serological tests
Detect antibodies against virus ina patient
Use antibodies to identify viruses in neutralization tests, viral hemagglutination, and Western blot
Nucleic acids
PCR: Polymerase chain reaction
RT-aPCR test for COVID-19
What are prions?
Infectious proteins
Proteinaceous infectious particles
Cause transmissible spongiform encephalopathies (TSEs)
Who discovered prions and linked it to scrapie?
American Neurobiologist, Stanley Pruisiner, in 1982
List the known prion diseases/TSEs.
Scrapie (goats, sheep)
Bovine spongiform (mad cow disease)
Feline spongiform (mad cat disease)
Creutzfeldt-Jakob disease (CJD)
Fatal familial insomnia
Gerstmann-Straussler-Scheinker disease (GSS)
Kuru, “laughing death”
Why are prion diseases dangerous? Treatment?
ALL FATAL neurological degeneration,
Deposition of fibrils in brain
& loss of brain matter
Slow progression (years to symptoms)
Large vacuoles form in brain
Treatment
No specific treatment
No vaccines
What are the general characteristics of prion diseases?
Prion PrPs are resistant to digestion by proteases
Antimicrobials are no effective for Prions
Cannot be destroyed by cooking or normal sterilization
Requires incineration (high temperature than normal autoclaving method)
How can we prevent getting and spreading prion diseases?
Rely on infection control measures
Incineration
Describe the pathogenicity of prion diseases
Infectious prions survive acid digestion
Penetrate gut mucosa
Amplified in dendritic cells in lymphatic tissues
Spread to spleen
Spread to CNS (central nervous system) via sympathetic nerves in spinal cord
PrPc to prion PrP SC
What are the clinical features of prion disease?
Relatively late in life
Rapidly progressive dementia
Behavioral disturbances
Ataxia (can’t control body)
Death within one year (once diagnosis)
No effect of antimicrobials
How can we diagnose prion diseases?
Brain tissue post-mortem
ELISA
Western Blotting
Nasal brushing procedure
