Microbiology Chapter 16
Arrange these events in the replication cycle of the E. coli phage lambda according to the order in which they occur.
1) Lambda phage DNA integrates 2) Deintegration event, which includes some bacterial genes 3) Replication of viral DNA with incorprated host genes 4) Infection of new cell with defective virus. 5) Bacterial genes become stably incorporated into a recipient cell's chromosome
How many types of DNA excision repair systems have been characterized?
2
Vancomycin-resistant Staphylococcus aureus (VRSA) was first isolated from a Michigan patient in what year?
2002
Inherent resistance to antibiotics could be due to which one of these?
A particular structural feature of the bacterial cell
Infectious disease processes induced by bacterial or fungal toxins in the _______ is termed septicemia.
Blood
A chemical agent that causes cancer is specifically called a(n) ________.
Carcinogen
In simplified terms, when a microorganism establishes a site on or within a host allowing replication, _________ has occurred.
Colonization
A bacteria cell that is able to take up DNA and be transformed is said to be __________.
Competent
The major conclusion of Hayes' 1952 experiments, which demonstrated the existence of F+ and F- stains, was that gene transfer by _________.
Conjugation is unidirectional
During which phase of the infectious disease process do the signs and symptoms begin to disappear?
Convalescence
Plasmids that can exist either independently or integrated into the host chromosome are called __________.
Episomes
Microbial pathogens that only grow and replicate outside of a host cell are typically called ________ pathogens.
Extracellular
A mutation that leads to a wild type organism mutating to a mutant form is called a(n) ________ mutation.
Forward
The major mechanism by which bacteria and archaea evolve (acquire novel genes) is __________.
Horizontal gene transfer
In one example of a relationship between two organisms, a(n) ________ is a larger organism that supports the survival and growth of a smaller organism.
Host
During the illness period of an infectious disease process, hot _______ responses are typically triggered.
Immune
Mutations that result from exposure to a physical or chemical agent (mutagen) are known as ______ mutations.
Induced
A(n) __________ is the natural environmental location in which the pathogen normally resides.
Reservoir
A second mutation that occurs at a different site from the first mutation, which returns the mutant back to the wild-type phenotype, is a(n) _________ mutation.
Reverse
An allele is most likely to persist in a population if it confers a survival advantage under _________ pressure.
Selective
When a microorganism is restricted to infecting only a particular cell or tissue type, this is known as a(n) __________.
Tropism
Match each protein or enzyme involved in the SOS response with it major function.
- DinB: Also called DNA polymerase IV; synthesize DNA across lesions - LexA: A key transcriptional repressor; its destruction initiates the SOS response - RecA: Binds to damaged DNA, initiating recombinational repai and coprotease activity - SfiA: Protein that blocks cell division - UmuCD: Also called DNA polymerase V; synthesizes DNA across lesions
Hfr stains of bacteria are so named because they undergo a _________ (high/low) frequency of ________.
- High - Recombination
Arrange these steps involved with Bernard Davis' U-tube experiment that proved direct cell contact is required for bacterial conjugation according to the order in which they were performed.
1) U-tube filled with growth medium 2) Each side of U-tube inoculated with a different E. coli auxotroph 3) Medium pumped back and forth through filter, incubation 4) Plate E. coli on minimal medium 5) Note absence of colonies, indicating lack of gene transfer
The type of antibiotic resistance that is due to a change in the genome of a bacterium that converts it from a sensitive cell to a resistant cell is called _________ resistance.
Acquired
In ________ transmission, a pathogen is often sneezed or coughed into the air and suspended in dust, droplet nuclei, or larger respiratory droplets.
Airborne
Septic shock is the net negative effect of _________.
Indirect stimulation of macrophages and other host systems leading to fever and coagulation disruptions
A high LD50 value means _______.
Very large numbers of microorganisms are required to kill an infected organism.
A low ID50 value means _________.
Very small numbers of microorganisms are required to induce an infectious disease state.
Which of the following is a general class of molecules that enables a microorganism to cause host cell or tissue damage?
Virulence factors
Bacteriophages that lyse their host cells soon after infection are called __________ bacteriophages.
Virulent
An infectious disease that is transmitted from an animal to a human is termed a(n) __________.
Zoonosis
Select the three mechanisms by which pathogens can actively penetrate host mucous membranes and epithelial tissue.
- Secretion of enzymes that attack extracellular matrix and basement membranes - Secretion of enzymes that degrade the glycocalyx of cells - Disruption of host cell surface via microbe-secreted substances
Select any mechanism that is a source of horizontal gene transfer in bacteria.
- Transformation - Transduction - Conjugation
The ________ test uses several "tester" strains of Salmonella to determine whether a particular substance is a mutagen.
Ames
Which of the following terms best describe the presence of viable bacteria in the bloodstream?
Bacteremia
Damaged or unnatural bases are removed by DNA glycosylases during which type of DNA repair?
Base excision repiar
A(n) _________ is a complex heterogeneous community formed by microbes usually within their natural environment but the have also been found "stuck" to medical plastics such as catheters and heart stints.
Biofilm
In bacteria, conjugation refers to the transfer of DNA by _________.
Cell-to-cell contact
During DNA replication, the ability of DNA polymerase to detect and correct errors before the next nucleotide is added is called DNA __________.
Proofreading
Match each example of a chemical mutagen with the type of DNA damage it can cause.
- 5-bromouracil: Base analogue that causes mismatching - Acridine orange: Intercalating agent - Hydroxylamine: Hydroxylase cytosine - Nitrogen mustard: Alkylating agent - Nitrous oxide: Deaminates bases
The diagram illustrates the genetic changes that result from different types of mutation. Match the letter of each illustrated type of mutation with the appropriate name.
- A: Silent mutation - B: Missense mutation - C: Nonsense mutation - D: Frameshift mutation
Match each mycotoxin with its best description.
- Aflatoxin: Approximately 18 different types; affect the liver, extremely carcinogenic, mutagenic, and immunosuppressive. - Ergots: Alkaloids with varying physiological effects, including hallucinations. One alkaloid in the group is lysergic acid, or LSD. - Stachybotry trichothecene mycotoxins: Induce inflammation; potent inhibitors of DNA, RNA, nad protein synthesis; disrupt surfactant , phospholipids in the lungs, and may lead to pathological changes in tissue.
Select three general effects of aflatoxins.
- Carcinogenic - Immunosuppressive - Mutagenic
Match each component of the mismatch repair system of E. coli with its function.
- DNA ligase: Connects the newly synthesized DNA with the old DNA - DNA polymerase: Replaces nucelotides that were excised - MutH: Removes DNA around a mismatch - MutS: Scans newly replicated DNA for mismatches
Which two of these scenarios would be likely to trigger an SOS response?
- DNA synthesis has stopped. - "Regular" DNA repair mechanisms are unable to fix DNA.
Which statements correctly describe missense mutations?
- Effects range from no change to complete loss of normal gene function. - They involve a single base substitution that changes a codon for one amino acid into another.
Select three typical systemic effects of lipid A on host organisms from the following list.
- Weakness - Fever - Shock
The time period between a pathogen enters a host and the development of symptoms is called the _______ period and it will vary from disease to disease.
Incubation
_______ is the ability of a microorganism to establish a discrete focal point of infection, which is often sufficient to induce a disease state.
Infectivity
Transposases are enzymes that recognize the ends of a(n) _________.
Insertion sequence
The lambda phage of E. coli is a temperate bacteriophage, meaning that it
Inserts its genome into the chromosome of its host
Which of the following descriptions best matches vector-borne transmission?
Lyme disease contracted through a bite from a tick.
The general term for inheritable changes in DNA sequence is ________.
Mutations
Match each mechanism of bacterial resistance to antibiotics with the best description.
- Alteration of target: Terminal D-alanine in peptidoglycan changes to D-lactate - Alternate pathways: Use of performed folic acid rather than synthesis - Drug inactivation: Hydrolysis of beta-lactam ring by beta-lactamase - Efflux pumps: Antiport mechanism where protons enter cell as drug levels
Which of these are types of chemical mutagens?
- Base analogs - DNA-modifying agents - Intercalating agents
Select all examples of common vehicles that could be referred to as fomites.
- Bedding - Drinking vessels - Surgical instruments
Which of these are correct statements about nonsense mutations?
- By definition, they always produce stop codons - Effects range from mild to complete loss of normal gene function - They cause the early termination of translation
A successful pathogen will utilize virulence factors, for example, to ________ and/or _________.
- Evade host immune defenses - Out-compete host cell for nutrients
Regarding airborne transmission of infections, which of the following are characteristics of droplets (not droplet nuclei)?
- Fall to the ground and other surfaces after remaining in the air for only a short distance from their point of origin. - Form when saliva and mucus are placed under force - 5 micrometers or more in diameter
Match each fate of donor DNA taken up by a bacterial cell with the most likely outcome.
- Integration of donor DNA with recipient DNA: Recombinant genome replicates, forming a population of stable recombinants - Donor DNA is a plasmid: Donor DNA replicates independently, forming a population of stable recombinants - Donor DNA remains in cytoplasm and is unable to replicate: As cell replicates, donor DNA is eventually lost - Host restriction occurs: Donor DNA is degraded
Which of these features are common to a majority of transposable elements?
- Inverted repeats - Gene recombinase (e.g., transposase)
Select all correct statements regarding site-specific recombination.
- It occurs at specific target sites in DNA molecules. - It is used by transposable elements - It is used by some viruses - It is catalyzed by recombinases
Which of these are synonyms for genetic elements that can move into and out of genomes?
- Jumping genes - Mobile genetic elements - Transposable elements
Which of the following are examples of infectious diseases spread by arthropod vectors?
- Lyme disease - Plague - Malaria
Which of these are specific components of the mismatch DNA repair system of E. coli?
- MutH - MutS - DNA polymerase - DNA ligase
Which of the following are properties of endotoxins?
- Only weakly immunogenic (not a strong stimulator of immune responses) - Heat stable - A component of the microbe itself; not secreted - Characterized as component of Gram-negative cell wall outer membrane
Identify which three of the following are required for a microorganism to survive within a host.
- Protection from harmful elements - A suitable environment for growth and replication. - A source of nutrients
Select all correct statements regarding homologous recombination.
- Similar or identical DNA strands are broken and reunited - RecA protein is involved - It is the most common mechanism of DNA recombination
Which of these descriptions apply to auxotrophs?
- They are unable to grow on medium lacking a particular molecule, where the wild-type strain could grow. - They are biochemical mutants - They have conditional phenotype
Which of these two most common techniques used to make bacteria artificially competent in the laboratory?
- Treatment with calcium chloride - Electrical shock
Arrange these events of generalized transduction according to the order in which they occur.
1) A bacteriophage infects the cell. 2) Bacterial DNA is partially degraded. 3) Fragments of bacterial DNA are mistakenly packaged 4) A generalized transducing particle injects DNA into another cells. 5) Double-stranded DNA is incorporated into the chromosome of the recipient cell.
Arrange these steps in rolling-circle replication according to the order in which they occur.
1) One strand of circular DNA is nicked 2) 3'-hydroxyl end of DNA is lengthened 3) Complementary DNA strand is synthesized 4) DNA may move using a type IV secretion system for transfer to another cell
Arrange these selected steps in the Ames test for mutagenic chemicals according to the order in which they are performed.
1) Test substance and a small amount of histidine are mixed in molten agar 2) Bacteria are added to plates 3) Plates are incubated for two to three days 4) Visible colonies are counted 5) Number of colonies are compared to controls with no test substance
Rank these steps in Hfr conjugation according to the order in which they occur.
1) The integrated F factor is nicked at its oriT site. 2) Part of the F factor begins to move into the recipient cell. 3) Part of the donor cell's chromosome is transferred. 4) Transfer stops; usually before entire F factor is transferred.
A bacterium that has been infected by a temperate bacteriophage, and is therefore carrying a prophage is known as a(n) ___________.
Lysogen
The general term for toxins produced by fungi is _________.
Mycotoxin
Point mutations that result in a new stop codon are specifically called _________ mutations.
Nonsense
The type of DNA repair that requires UvrABC endonuclease, DNA polymerase I, and DNA ligase is __________.
Nucleotide excision repair
An organism that infects a host when it gets out of its typical niche (normal location in the body) is a(n) ________.
Opportunistic pathogen
Which of the following terms best matches a large segment (10-200 kilobases) of bacterial chromosomal and plasmid DNA that encodes virulence factors?
Pathogenicity island
Repair thymine dimers by a process involving visible light is called
Photoreactivation
In relation to infectious agents, the skin, respiratory system, gastrointestinal tract, urogenital system, and conjuctiva of the eye are all examples of _______.
Portals of entry through which infectious agents may gain access to host tissues
The genome of a temperate bacteriophage that has been inserted into a bacterial genome is called a(n) __________.
Prophage
The wild-type of a bacterium that is a chemoorganotroph able to grow on a minimal medium containing only salts and a carbon source is known as a(n) __________.
Prototroph
Plasmids that carry genes for resistance to one or more antibiotics are called _________ plasmids.
R
The organisms produced when nucleic acids are rearranged or combined to produce a new genotype are most commonly called _______.
Recombinants
Damage to DNA in which both bases of a pair are missing or damaged, or where there is a gap opposite a lesion, is usually repaired by a process called ________ repair.
Recombination
Point mutations that change the nucleotide sequence of a codon but do not change the amino acid encoded by that codon are specifically called ___________ mutations.
Silent
A disease ________ is a set of signs and symptoms that are characteristic of the disease.
Syndrome
Which of the following is the best definition for pathogenicity?
The ability of an organism to cause disease.
Horizontal gene transfer is defined as
The transfer of genes from one independent, mature organism to another
Which one of the following best describes the prodomal stage of an infectious disease?
There is an onset of signs and symptoms, but they are not yet specific enough for disease diagnosis.
Which of the following items describes a substance that alters the normal metabolism of host cells with overall negative effects on the host organism?
Toxin
The horizontal transfer of bacterial genes by bacteriophages is called ________.
Transduction
The process of taking up DNA from the surroundings, and maintenance of the DNA in a heritable form, is called ________.
Transformation
Specific DNA segments that can repeatedly insert into one or more sites or into one or more genomes are called the __________ elements.
Transposable
The enzyme that recognizes inverted repeats, and cuts DNA to remove a mobile genetic element is _______.
Transposase
A(n) _________ is an organism that facilitates the spread of disease from one host to another. Examples include mosquitoes, ticks, and fleas (among others).
Vector
Another term for the transfer of genes from parents to progeny is _______.
Vertical gene transfer
