Microbiology Exam 2
How can auxotroph be studied in horizontal gene transfer?
Auxotrophs provide a great strategy to select and identify cells that have successfully taken up foreign genes introduced by horizontal gene transfer The growth of transformed cells on selective media indicates successful gene transfer and integration
Three types of penicillin, difference between Penicillin G and V
Natural penicillins: G and V (narrow spectrum, susceptible to penicillnase) i. G: requires injection ii. V: can be taken orally Semisynthetic penicillins Extended-spectrum penicillins
How bacterial viruses enter cells (bacteriophage)
Phage will not enter cell, instead viral DNA is injected into host cell
Inhibition of nucleic acid replication and transcription: Quinolones
Quinolones: antibacterial compounds that interfere with DNA gyrase Quinolones kill cell by breaking in DNA
Phenotype: definition, what it depends on
actual, expressed properties of an organism's characteristics Depends on genotype and environment Example: height, hair color
Genome
entire genetic information in a cell or virus Include its chromosomes and plasmids
Chromosome: definition, what does it contain, where is it found
structures containing DNA that physically carry hereditary information; chromosomes contain essential genes. Main genetic element of prokaryotes
Genomics
the sequencing and molecular characterization of genomes
Genetics
the study of heredity, include study of genes
Microbiome
collection of all microbes, such as bacteria, fungi, viruses, and their genes, that naturally live on our bodies and inside us. Shorter version: microbes+ genomes+ habitat they are found
Why are gram negative bacteria more resistant to penicillin or in general antibiotics? Outer membrane, few peptide, efflux pumps, enzymes
*In general, the lipopolysaccharide outer membrane of gram-negative bacteria forms a barrier that inhibits the entry of antibiotics + Additionally, gram-negative bacteria have fewer peptide cross-bridges, which makes it harder for antibiotics that target cell walls + Gram negative can also contain efflux pumps that actively expel antibiotics and the presence of enzymes like beta-lactamases that can break down antibiotics.
How does the attachment process contribute to virus-host specificity?
+ Attachment of virion to host cell is highly specific. + Requires specific cellular receptors on the surface of a susceptible host and its infecting virus + For example, HIV targets specific receptors : CD4 and CCR5
What are B-lactam antibiotics? What is the mode of action of B-lactam antibiotics? How does it work?
+ B-lactam antibiotics: Penicillin, Cephalosporins + Contain B- lactam ring + B-lactam antibiotics mode of action: Inhibition of Cell wall synthesis + Prevents the cross linking of peptidoglycan, interfering with cell wall construction (especially gram positive). Ultimately leads to cell lysis. Only affects actively growing cells.
What is a plaque-forming unit?
+ Each plaque corresponds to a single virus - Expressed as plaque forming unit
What is F pilus? Where is it typically found? Give an example. Why is it done?
+ F pilus or sex pilus: a bridge/channel formed during conjugation + Typically found on the surface of donor bacterial cells (F+ cells, Hfr cells) involved in conjugation + Ex: Found on F+ strains of Escherichia coli + Why: to transfer DNA during conjugation
What types of genes do plasmids carry in general? What do specific plasmids carry?
+ In general, plasmids carry non essential genes- genes not needed for survival of the bacteria. If plasma leaves cell, the bacteria will not die + Specific plasmids have specific genes. For example, conjugative and R plasmid have specific genes
Extended spectrum penicillins
+ New penicillins that were further modified to be effective to not only gram-positive, but to many gram-negative bacteria as well. Still not resistant to penicillinases Examples of some: Ampicillin, Amoxicillin
Difference between RNA- and RNA + virus: definition, examples
+ RNA+: genome can serve as mRNA directly for translation. Examples: Influenza, Corona virus, HIV + RNA- : requires transcription to create mRNA for protein synthesis
What is a viroid?
+ Short pieces of naked RNA, only 300 to 400 nucleotides long, with no protein coat (capsid) + Some viroids, called virusoids, are enclosed in a protein coat
Virus and Plasmid: Similarities, Differences
+ Similarities: rely on host cell to function + Differences: Viruses can exist outside of a cell, plasmids can not (must be protected inside of the cell) + Viruses: can contain RNA or DNA. Plasmid: contain DNA
Complex viruses: definition, example, structure, definition of capsid
+ Some viruses, particularly bacterial viruses, have complicated structures + Example of this is a bacteriophage + Contain icosahedral head (capsid), sheath, helical tail + Capsid: protein coat that surrounds and protects the genetic material of a virus.
Enveloped vs. non-enveloped viruses Shape of enveloped virus, what envelope is made up of, how is envelope obtained, non enveloped
+ The capsids of some viruses is covered by an envelope. + Enveloped viruses are roughly spherical + Envelope made up of: combination of lipids, proteins, and carbohydrates + A viral envelope is obtained by budding through a host cell's membrane Example: Coronavirus, HIV +Viruses whose capsids aren't covered by an envelope are known as nonenveloped viruses.
Provide an example of a latent viral infection (Cold sores)
+ The classic example of such a latent infection is the infection of the skin by Simplexvirus, which produces cold sores. This virus inhabits the host's nerve cells but causes no damage until it is activated by a stimulus such as fever or sunburn—hence the term fever blister.
HIV order of infection
+ The first cells to be infected are macrophages and dendritic cells. These cells are present in mucosal tissues which are the entry points. + In these cell types replication is inefficient but enough to start HIV spread to other cells. + Infected macrophages and dendritic cells are transported to the lymph nodes and other lymphatic organs where activated CD4 T cells are found. From there the infection spreads rapidly.
Inhibition of protein synthesis: Chloramphenicol
+ binds to 50S subunit and inhibits formation of peptide bond + Dangerous side effects: suppression of bone marrow activity. Affects formation of red blood cells
Why were semisynthetic penicillins made? Disadvantages of natural penicillins, definition of pencillnases, why were semisynthetic penicillins developed
+Disadvantages of natural penicillins: narrow spectrum susceptibility to penicillinases + Penicillinases: enzymes produced by many bacteria, most notably Staphylococcus species, that cleave the β-lactam ring of the penicillin molecule + Penicillnases are also called B-lactamases + A large number of semisynthetic penicillins have been developed in attempts to overcome this disadvantage of natural penicillins
Differentiate persistent viral infections from latent viral infections.
+Latent viral infection: virus remains in asymptomatic host cell for long periods without producing infection Examples: Cold sores, shingles + Persistent (or chronic) viral infection: Disease process occurs over a long period. Generally fatal + Different from latent because detectable infectious virus gradually build up over a long period, rather than appearing suddenly Examples: HIV and HPV
Injury to plasma: Polymyxin B Definition, how does it work? What can the lead to?
+bactericidal antibiotic effective against gram-negative bacteria +it acts by binding to the outer membrane of the cell wall. +Disruption can lead to the leakage of cellular contents and cell death
What disturbs the microbiome?
- Antibiotics - Hygiene hypothesis: early childhood exposure protects against allergies - C-sections - Diet changes
Growing bacteriophages in laboratory: plaque method how they can be grown, importance of solid media, steps
- Bacteriophages can be grown either in suspensions of bacteria in liquid media or in bacterial cultures on solid media. - The use of solid media makes it possible to use the plaque method to detect and count viruses. How it's done: 1. Pour mixture containing molten top agar, bacterial cells, and dilute phage suspension onto solidified nutrient agar plate 2. Let solidify 3. Incubate
Canine Parvovirus (CPV) pathogen presentation How long CPV incubates for, when infections occur, steps for spreading infection
- CPV incubates for 3-7 days between infection and onset of symptoms and needs help of rapidly dividing cells to cause disease - Most infections occur in spring/summer - Dogs can be asymptomatic and still spread infection Step 1: Virus attacks tonsils/lymph nodes in the throat and invades white blood cells. Spends 1-2 days replicating itself Step 2: Moves into blood stream and targets young immune cells in bone marrow and small intestine. Stops body from properly absorbing nutrients, preventing fluid loss into stool, and preventing bacteria from moving from gut into body in GI tract
Why is it useful to use cell culture for viral research? Definition, why is it important
- Cell cultures consist of cells grown in culture media in the laboratory. Used to cultivate animal viruses. - Provides a controlled environment for viral replication and propagation (growth); allows researchers to study viruses in a systematic manner. Additionally, reduces need for live animals or embryonated eggs which are most costly.
What RNA does HIV contain? What cells does HIV infect?
- Contains two identical + strands of RNA - Infects CD4 T cells (helper T cells)
Why causes an antibiotic to be broad or narrow?
- Gram-positive and gram-negative bacteria vary in their sensitivity to antibiotics - Specifically for gram-negative bacteria, there is a lipopolysaccharide outer layer of gram-negative bacteria and porins that form water-filled channels across this layer - Drugs that pass through the porin channels must be relatively small and preferably hydrophilic. Drugs that are lipophilic or especially large do not enter gram- negative bacteria readily.
Contrast Hfr, F+, F- cells
- Hfr cell (high frequency recombination) have F plasmids integrated with the chromosomal DNA. Hfr would transfer both the plasma and chromosomal DNA. Produces 1000 times as many recombinants than a normal F+ strain - With F+, only the F plasmid is transferred; the chromosomal DNA is not. - F- cells lack the F factor and can receive it from Hfr, F+ cells
What are some differences between semisynthetic penicillins and natural penicillins?
- Natural penicillin: produced by Penicillium mold - Semisynthetic penicillins: part of the penicillin is produced by the mold, and other part is added synthetically.
HIV Statistics, Originate, how it spreads
- New HIV infections have reduced by 40% since the peak in 1998 - AlD-related death have been reduced by 60% since 2004 - Originate - jumped from chimpanzees to humans in sub-Saharan Africa - Spread - body fluid containing the virus carries the particle to a mucosal membrane or blood stream of uninfected person -blood -semen -breast milk
Canine Parvovirus (CPV) pathogen presentation Deaths per year, age puppies are at risk, mortality rate
- Parvo is not a reportable disease, so no accurate numbers on how many cases and deaths each year - Puppies 6 months or younger are at most risk. Over 90% mortality rate if left untreated
How animal viruses enter cells
- Penetration through Endocytosis or Fusion: Once attached, animal viruses can enter the host cell in one of two main ways: 1. Endocytosis: host cell engulfs the virus by forming a vesicle around it. The virus is then transported into the cell where it can release its genetic material. If enveloped can undergo fusion: 2. Fusion: viral envelope fuses with the plasma membrane and releases the capsid into the cell's cytoplasm
Why are continuous cell lines of more practical use than primary cell lines for culturing viruses?
- Primary cell lines tend to die out after only a few generations. - When viruses are routinely grown in a laboratory, continuous cell lines are used. These are transformed (cancerous) cells that can be maintained through an indefinite number of generations.
Penicillinase-Resistant Penicillins (MRSA)
- Staphylococcal infections became resistant to penicillin due to a plasma-borne gene that produces an enzyme called β-lactamase - Antibiotics that were relatively resistant to this enzyme, such as the semisynthetic penicillin methicillin, were introduced, but resistance to them also soon appeared - Thus the organisms were termed methicillin- resistant Staphylococcus aureus (MRSA) - Resistance became so prevalent that methicillin has been discontinued in the United States
Cytopathic effects in cell culture
- Viruses infecting such a monolayer sometimes cause the cells of the monolayer to deteriorate as they multiply. - Structure changes that occur in host cells as a result of viral infection, often leading to cell damage or death.
Plaques: definition, what lawns can be, what it results from, what does it indicate
- clear zones that develop on lawns of host cells. Lawns can be bacterial or tissue culture - Each plaque results from infection by a single virus - Indicates presence of viral replication.
Competence: definition, results from, 2 ways it can be seen, what is used for second way
- recipient cells capable of taking up donor DNA and being transformed - Competence results from alterations in the cell wall that make it permeable to large DNA molecules - In naturally transformable bacteria, competence is regulated - In other strains, specific procedures are necessary to make cells competent - Electricity can be used to force cells to take up DNA (electroporation)
Plasmids definition, size, how can they move
- self-replicating (replicate separately from chromosomes) -gene-containing, double stranded, circular pieces of DNA -less than 5% the size of the bacterial chromosome - Plasmids can be can move from one chromosome to another or from one cell to another through conjugation
What did Alexander Fleming discover in 1928?
- the growth of Staphylococcus aureus was inhibited in the area surrounding the colony of a mold that had contaminated a Petri plate Mold was Identified as Penicillium notatum. Today is known as penicillium chrysogenum
Difference between conjugation, transformation, transduction
-Conjugation: genetic transfer that involves cell-to-cell contact (can be through sex pilus) - Transformation: genetic transfer in which bacterium takes up external piece of DNA floating in its environment. - Transduction: transfer of bacterial DNA from donor cell to recipient cell by a virus that infects bacteria (bacteriophage)
Transformation: definition, 2 ways it can be done, what is used for the second way
-genetic transfer in which bacterium takes up external piece of DNA floating in its environment. - Can be done naturally (highly regulated, multistep process) - However, in other strains, specific procedures are necessary to make cells competent for transformation. - Electricity can be used to force cells to take up DNA (electroporation)
Mechanism of Transformation (steps)
1. Recipient cell takes up donor DNA 2. Donor DNA aligns with complimentary bases 3. Recombination occurs between donor DNA and recipient DNA
What is an auxotroph?
1. A mutant microorganism with a nutritional requirement that is absent in the parent. Auxotrophic mutants will not grow unless the media contains one or more specific cellular building blocks Ex: an auxotroph may lack an enzyme needed to synthesize a particular amino acid and will therefore require that amino acid as a growth factor in its nutrient medium
Steps in transduction
1. A phage infects the donor bacterial cell. 2. Phage DNA and proteins are made, and the bacterial chromosome is broken into pieces. 3. Occasionally during phage assembly, pieces of bacterial DNA are packaged in a phage capsid. Then the donor cell lyses and releases phage particles containing bacterial DNA. 4. A phage carrying bacterial DNA infects a new host cell, the recipient cell. 5. Recombination can occur, producing a recombinant cell with a genotype different from both the donor and recipient cells.
What are the ways that researchers are working to discover new antibiotics?
1. AI screening: used an AI algorithm to screen thousands of antibacterial molecules in an attempt to predict new structural classes. Result of the AI screening: researchers were able to identify a new antibacterial compound which they named abaucin. 2. Looking in soil: Soil is filled with diverse microorganisms, including bacteria and fungi, which produce a wide array of natural compounds, some of which may have antibiotic properties
What is the HIV replication cycle? (7 stages)
1. Binding: virion binding to CD4 and chemokine receptor 2. Fusion: HIV membrane fuses with cell membrane; entry of viral genome into cytoplasm 3. Reverse transcription: transcribes DNA from RNA template, synthesis of proviral DNA 4. Integration: integration of provirus into cell genome 5. Replication: cytokine activation, transcription of HIV genome, transport of spliced and unspliced RNAs to cytoplasm 6. Assembly: synthesis of HIV proteins and assembly of virion core structure 7. Budding: expression of gp120/gp41 on cell surface, budding of mature virion
Conjugative plasmid
1. Conjugative plasmids: carries genes for sex pili and for the transfer of the plasmid to another cell. Conjugal transfer is controlled by tra genes on plasmid
What is the minimum inhibitory concentration (MIC)? What is used? How is it determined?
1. Definition: smallest amount of an agent needed to inhibit growth of a microorganism Varies with the organism used, inoculum size, temp, pH, etc. 2. A microdilution or microtiter plate is used for testing for minimal inhibitory concentration (MIC) of antibiotics. 3. Determined through preparation of serial dilutions. After incubation, tubes are observed for bacterial growth
Why is HIV so hard to cure?
1. HIV mutates rapidly Antibodies produced become obsolete (no longer can be used) 2. HIV hides inside infected cells in a latent state 3. HIV kills important cells of the immune system (CD4 Helper T cells)
Difference between broad-spectrum and narrow-spectrum antibiotics Specific example for each
1. Narrow- spectrum antibiotics: antibiotics that affect a narrow range of different microbial types. Either Gram + OR Gram - Ex: Penicillin G (natural penicillin) affects mostly gram-positive bacteria 2. Broad-spectrum antibiotics: antibiotics that affect a broad range of microbial types. Both Gram + AND Gram - bacteria Ex: Quinolones can affect both gram-positive and gram-negative bacteria
What enzymes are important to HIV and what do they do?
1. Reverse transcriptase: transcribes RNA into double-stranded DNA. Needed for HIV to infect CD4 cells. 2. Protease: cleaving lengthy viral precursor proteins into smaller structural proteins 3. Integrase: viral DNA becomes integrated with the host's DNA
How is vertical transfer different from horizontal transfer?
1. Vertical gene transfer (cell division): genes are passed from an organism to its offspring (across numerous generations) Plants and animals transmit their genes by vertical transmission 2. Horizontal gene transfer: transfer of genes between two organisms in the same generation. Done in bacteria Three types of horizontal gene transfer: conjugation, transformation, and transduction. Non cell division
Compare conjugation between the following pairs: F+ to F- , F+ to Hfr Hfr to F-. Contrast Hfr, F+, F- and cells?
1. When an F factor (a plasmid) is transferred from a donor (F +) to a recipient (F - ), the F - cell is converted to an F+ cell. 2. In some cells carrying F factors, the factor integrates into the chromosome, converting the F+ cell to an Hfr cell (high frequency of recombination) 3. When an Hfr donor passes a portion of its chromosome into an F - recipient, a recombinant F - cell results. Remains F- because it did not receive a complete F factor during conjugation
What is a semisynthetic antibiotic?
A natural antibiotic that has been chemically modified in the laboratory to enhance efficacy
Functions of plasmids (3)
Antibiotic resistance, toxin resistance, virulence factors (Example of virulence factors: tetanus neurotoxin, heat-labile enterotoxin, and staphylococcal enterotoxin D.)
What are the major modes of action of the major antimicrobial targets? Please give an example of one antibiotic from each category.
Antimicrobial drugs target certain essential functions of the microbe Mechanisms of action include: 1. Inhibition of cell wall synthesis: Penicillin, Cephalosporins, 2. Inhibition of protein synthesis: Chloramphenicol, 3. Inhibition of nucleic acid replication and transcription: Quinolones 4. Injury to plasma: Polymyxin B 5. Inhibition of essential metabolite synthesis: Sulfanilamide
How are B-lactam antibiotics inactivated by bacteria?
Bacteria can break down B- lactam antibiotics using special enzymes called B-lactamases, which render the antibiotics ineffective.
Why are anti-viral drugs so difficult to design?
Because viruses replicate within the host's cells, very often using the genetic and metabolic mechanisms of the host's own cells, it's relatively difficult to target the virus without damaging the host's cellular machinery.
Growing animal viruses in laboratory: normal vs transformed cells
By using cell cultures Steps 1. Tissues are treated with enzymes to separate cells 2. Cells are suspended in culture medium 3. Normal cells (primary cells): grow in a monolayer across glass or plastic container Transformed cells (continuous cell cultures): do not grow in monolayer
What is the mutation that makes people resistant to HIV infection?
CCR5 Δ32 Mutation + Some people are born with a mutation that prevents CCR5 from appearing on cells, making them resistant to HIV + CCR5 co-receptor: door that allows HIV entrance into the cell. HIV must bind to it to enter + Some experimental gene therapy approaches aim to mimic this mutation in AIDS patients
What are three main ways that we can categorize viruses?
Coating 1. Enveloped 2. Non enveloped Genes 1. DNA 2. RNA Host 1. Plant, Animal, Phage
Functions of microbiome
Digestion, vitamin production, pathogen protection, metabolic rate, immune regulation, odor, behavior
What kinds of enzymes can be found within the virions of general and specific viruses?
For RNA- and RNA + viruses RNA dependent RNA polymerase: synthesizes a complementary RNA + strand from an RNA - template For DNA virus DNA- dependent DNA polymerase: synthesizes DNA strand during DNA synthesis For retro viruses Reverse transcriptase (an RNA-dependent DNA polymerase): transcribes RNA into double-stranded DNA For specific viruses - HIV (retrovirus) has reverse transcriptase but also: Integrase: integrate its viral DNA into the DNA of the host CD4 cell Protease: cleaves lengthy viral precursor proteins into smaller structural proteins
Describe Griffith's experiment Pt. 1
Frederick Griffith in England in 1928: demonstrated genetic transformation while working with two strains of Streptococcus pneumoniae. One, a virulent strain, has a polysaccharide capsule that prevents phagocytosis. The bacteria grow and cause pneumonia. The other, an avirulent strain, lacks the capsule and does not cause disease. Griffith was interested in determining whether injections of heat-killed bacteria of the encapsulated strain could be used to vaccinate mice against pneumonia.
What are the targets/inhibitors of HAART? Definition, Inhibitors
HAART: highly active antiretroviral treatment. Consists of administering drug combinations Entry and fusion inhibitors, reverse transcriptase inhibitors, integrase inhibitors, protease inhibitors
In Karl Klose's TED talk, what did he call the three methods of horizontal transfer? And the three mechanisms of antibiotic resistance? Here is the link again, in case you still need to watch it: Karl Klose - Rise of the Superbug (11 min.) https://www.youtube.com/watch?v=ikZQPB45Zbw
Horizontal transfer: sharing antibiotic resistant genes 1. Funeral grab (transformation): Bacteria #1 died and released genes into surroundings, Bacteria #2 will pick up some of these genes and possess Bacteria #1 attributes 2. Viral Pass (transduction): Virus will infect Bacteria #1 and pick on some of its genes and then inject these genes into Bacteria #2 3. Sex pass (conjugation): Bacteria #1 builds a bridge to Bacteria #2 through which genes are passed Mechanisms of antibiotic resistance 1. Up-chuck: antibiotic target something specific inside bacterial cell but as soon as antibiotic gets inside, the bacteria barfs it back up. Ex: resistance to tetracycline 2. Stealth mode: antibiotic targets something specific inside bacterial cell but bacteria changes target just enough for antibiotic not to recognize it. Ex: resistance to streptomycin 3. Ballistic missile defense: bacteria makes type of weapon that goes out and finds antibiotic before antibiotic can find target Ex: technique used to be resistant to penicillin
Why must some types of virus contain enzymes in the virion in order for mRNA to be produced?
Host cells lack certain enzymes such as RNA-dependent RNA-polymerases, so virus must bring those enzymes in order to facilitate production and replication
Canine Parvovirus (CPV) pathogen presentation: Symptoms
Lethargy, inappetence, high fever, vomiting, diarrhea (hemorrhagic and nonhemorrhagic), abdominal pain
Microbi-OME vs micro-biOME
Microbi- OME: collection of genomes of microbes from a communitu Micro-BIOME: collection of microbes
What are the mechanisms that bacteria use to become resistant to antibiotics?
Organism lacks structure the antibiotic inhibits Organism is impermeable to antibiotic Organism can inactivate the antibiotic Organism may modify the target of the antibiotic Organism may develop a resistant biochemical pathway Organism may be able to pump out the antibiotic (efflux)
R plasmids (R factor): definition, what are they classified under, what do they contain
R plasmids: (resistance plasmids, R factor), group of plasmids that grants resistance to antibiotics and other growth inhibitors. Many are conjugative R plasmids contain: 1. Resistance transfer factor (RTF): contains genes for plasmid replication and conjugation (tra genes) 2. R- determinant: contains resistance genes that codes for the production of enzymes that inactivate certain drugs or toxic substances
What are the attributes of an ideal antibiotic?
Solubility in body fluids Selective Toxicity More toxic to microbes than to the host Toxicity is not easily altered through interactions Nonallergenic Stability Resistance is not easily acquired Long shelf-life Reasonable cost
Influences on gut microbiome composition (8) What birth mode is best?
Stress, exercise, environment, birth mode, diet, pet ownership, genetics, medication It's believed that vaginal birth is best for infant's microbiome compared to c section
Inhibition of essential metabolite synthesis
Sulfanilamide: analog of PABA (nucleic acid precursor) Blocks the synthesis of folic acid
How did the virus overcome that resistance?
The CCR5 Δ32 Mutation does not protect against all HIV. - Some strains of HIV can use alternative co-receptors for cell entry, such as CXCR4, which is not affected by the CCR5 mutation
What is the relationship between horizontal transfer and antibiotic resistance?
The harmless bacteria (normal microbiota) that are resistant to antibiotics can then pass this gene to harmful bacteria (pathogens) that do not yet have antibiotic resistance. Thus, horizontal gene transfer allows bacteria to indirectly become resistant to antibiotics
Transduction: definition, two types
Transduction: transfer of bacterial DNA from donor cell to recipient cell by a virus that infects bacteria (bacteriophage) - Generalized transduction, any bacterial genes can be transferred - Specialized transduction: only certain bacterial genes are transferred
Differentiate a virus from a bacterium.
Viruses 1. Contains intracellular parasite. 2. Can pass through bacteriological filters. 3. Sensitive to Interferon 4. Possess DNA or RNA 5. Contains a protein coat Typical Bacteria 1. Contains plasma membrane 2. Divides by binary fission 3. Possess both DNA and RNA 4. ATP generating metabolism 5. Contains ribosomes 6. Sensitive to antibiotics
Canine Parvovirus (CPV) pathogen presentation What is CPV? What is PVE? How does PVE spread?
What is CPV? - CPV is a small, non-enveloped, single-stranded DNA virus of the Parvoviridae family affecting dogs and other Canidae species - CPV Type 2 causes Canine Parvovirus Enteritis (PVE) - It is NOT a zoonotic virus What is PVE? - A highly contagious and potentially life threatening viral disease that causes extreme GI symptoms in puppies - Spreads via direct contact with infected dogs, feces, and vomit or through contaminated fomites - Global epidemic, leading cause of death in dogs worldwide
Bacteriophage Viral Multiplication (Lytic Cycle)
a. Bacteriophage 1. Attachment: Tail fibers attach to cell wall proteins 2. Entry: viral DNA is injected into host cell 3. Uncoating: not required 4. Biosynthesis: occurs in cytoplasm 5. Chronic infection: lysogeny (viral genome integrates with host genome, remains dormant) 6. Release: host cell is lysed, new virions are released
Griffith Experiment results demonstrating genetic transformation
a. Living encapsulated bacteria injected→ multiple colonies of encapsulated bacteria isolated → dead mouse b. Living nonencapsulated bacteria injected→ few colonies of nonencapsulated bacteria → healthy mouse c. Heat-killed encapsulated bacteria injected→ no colonies of encapsulated bacteria isolated → healthy mouse d. Combination of living nonencapsulated bacteria and heat-killed encapsulated bacteria injected→ multiple colonies of encapsulated bacteria → dead mouse Analysis: Somehow, the live nonencapsulated bacteria were transformed by the heat-killed (dead) encapsulated bacteria so that they acquired the ability to form capsules and therefore cause disease.
Bacteriostatic (antimicrobial agent)
an agent that inhibits bacterial growth
Bacteriocidal (antimicrobial agent)
an agent that kills
Animal Virus Viral Multiplication
b. Animal viruses: 1. Attachment sites are plasma membrane proteins and glycoproteins 2. Entry: capsid enters by receptor mediated endocytosis or fusion 3. Uncoating: enzymatic removal of capsid proteins 4. Biosynthesis occurs in nucleus (DNA viruses) or cytoplasm (RNA viruses) 5. Chronic infection: latency; slow viral infections; cancer 6. Release: enveloped viruses bud out, nonenveloped viruses rupture plasma membrane
Bacteriolytic (antimicrobial agent)
cells are killed and destroyed
How does the disc diffusion assay work? Goal of assay, what is zone inhibition, steps
determines susceptibility of an organism based upon the zone of inhibition of the organism Zone of inhibition: clear area where bacterial growth is inhibited by antibiotic How does it work: 1. Inoculate plate with a liquid culture of a test organism 2. Discs containing antimicrobial agents are placed on surface 3. Incubate for 24-28 hr 4. Test organism shows susceptibility to some agents, indicated by inhibition of bacterial growth of discs (zones of inhibition)
Genotype
genetic makeup—all its DNA—the information that codes for all the particular characteristics of the organism
Why does a virus need a host cell?
must be grown in living cells in order to replicate and reproduce
Gene
segments of DNA that code for functional products (except in some viruses, in which they are made of RNA)
Genetic code
set of rules that determine how a nucleotide sequence is converted into the amino acid sequence of a protein
Transponsons
small segments of DNA that can move (be "transposed") from one region of a DNA molecule to another.
What is selective toxicity?
the ability of a chemical to kill pathogenic microorganisms without adversely affecting (damaging) the host
Conjugation: definition, how its facilitated, donor and recipient
transfer of genetic material (usually plasmids) from one bacteria cell to another Cell-to-cell contact Typically facilitated by F pilus or sex pilus Donor cell: contains conjugative plasmid Recipient cell: does not contain plasmid
