Micriobio Exam 2

Please place the steps for animal virus replication in the correct sequence.

1. Virus attaches to receptors on the host cell cytoplasmic membrane. 2. Virus enters the host cell by fusion or endocytosis 3. Viral genome is uncoated. 4. Structural and catalytic viral genes are expressed 5. Multiple copies of the viral genome are synthesized 6. New viral particles assemble and mature. 7. New viral particles assemble and mature.

Look at the figure below, which shows fragments of DNA, cut by restriction endonucleases and separated by size on a gel. Which DNA samples are likely to be from the same bacterial strain?

2, 3, and 4

Explain the difference between a biotype and a serotype.

A biotype is the biochemical profile of a particular microorganism, while the serotype is the difference in its surface structures/antigens that will lead to separate immune responses from an organism (characterized by presence of different antibodies in the individual's serum).

Which of the following statements is/are TRUE?

A change in genotype can change the phenotype. An auxotroph has a different genotype than a prototroph. An auxotroph has a different phenotype than a prototroph.

Which of the following is required for prion replication?

Abnormal prion protein

Why is it virtually impossible to stamp out a disease caused by a zoonotic virus?

All of the above are correct.

Fungi are important because of their ability to

All of the above.

Prions

All of the above.

Fungi that are important for fermentation of fruits

All of the choices are correct.

Serological methods

All of the choices are correct.

Transposons

All of the choices are correct.

Which technique(s) is/are used to help identify and classify bacteria?

All of the choices are correct.

The three domain classification scheme uses

Archaea, Bacteria, Eucarya.

The reference for taxonomic descriptions of bacteria is

Bergey's Manual of Systematic Bacteriology.

Which of the following descriptions fits a chronic viral infection?

Characterized by continuous production of low levels of viral particles, potentially even in the absence of active symptoms of disease. The organism is usually still highly infectious during this time.

Identify all the fungi that are considered medically important from the choices below.

Cryptococcus neoformans Candida albicans Aspergillus species that produce aflatoxins

Organize the following taxonomic categories from the most inclusive to the least inclusive.

Domain Kingdom Phylum Class Order Family Genus Species

Please use the dichotomous key below to identify a bacterium with the following characteristics: stains pink in the Gram stain, produces no color when exposed to oxidase substrate, and produces both acid and gas when inoculated in lactose broth.

E. coli or other coliform

All mutagens are carcinogens but not all carcinogens are mutagens.

False

Label the following structures seen during the different states of fungal growth.

From Left to Right: Spore, Hypha, Mycelium

Which of the following statements about the economic impact of fungi is FALSE?

Fungi commonly cause serious human diseases that lead to loss of work hours.

Explain why HIV becomes resistant so quickly when a single drug is used therapeutically.

HIV utilizes reverse transcriptase to make a cDNA version of its RNA genome. This polymerase is "'sloppy," with a high rate of error and lack of a proofreading capability. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance.

Why are viroids resistant to nucleases?

Having a circular RNA "genome," they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA)

Is it as effective to take two antibiotics sequentially for an infection as it is to take them simultaneously, so long as the total length of time of the treatment is the same?

It depends. Provided that the majority of the infectious agent is killed off by the first drug, the likelihood that the few that are left would not also be killed by the second drug is low. However, simultaneous treatment should be more effective at eliminating all the microbes in the shortest time possible, and with the least probability of selection for multiple drug resistance mutations.

Two bacterial genes are transduced simultaneously. What does this suggest about their proximity to each other within the original host genome?

It's highly likely that the two genes are located next to each other in the original host cell chromosome. Since transduction relies on either mispackaging of bits of host cell DNA into non-functional virus units, or improper excision of lysogenic phage DNA from a host cell chromosome (carrying parts of the host cell DNA with it), the genes must lie close to each other to be transduced into a new cell simultaneously.

The series of steps used to connect an organism to a disease are known as

Koch's postulates.

Which of the following describes a latent viral infection?

Long periods of time with essentially zero viral replication, punctuated by outbreaks of active replication and disease manifestation. Infected individuals are largely non-infectious between outbreak periods.

Intracellular Gram-negative diplococci found in a urethral sample from a male is indicative of

Neisseria gonorrhea.

Place the helminth characteristics in the appropriate column.

Nematodes: cylindrical tapered body, roundworms, an example is pinworms, digestive tract including mouth and anus Cestodes: Flat ribbon-shaped bodies, tapeworms, lack digestive system absorb nutrients, immediate host include cattle and pigs, a tapeworm is an example Trematodes: flat leaf-shaped bodies, flukes, one opening for intake of nutrients one opening for exit of waste, an example is schistosomes

Please label the parts of a typical enveloped virus particle.

One in row by itself: Nucleoplasid From top to bottom: Spikes, matrix protein, nucleic acid, capsid, envelope

Match the type of protozoan with its identifying characteristic. Refer to figure 12.12 for assistance.

Parabasalids: Flagellated protists lacking mitochondria and living within a host organism. Includes Trichomonas vaginalis, causative agent of trich (a sexually transmitted infection). Diplomonads: Flagellated protists lacking mitochondria and living in anaerobic conditions. Includes Giardia lamblia, a common cause of diarrhea. Heteroloboseans: Prostists with an amoeboid form that can also form flagellated cells. Includes Naegleria fowleri, a brain-eating organism Apicomplexans: Parasites with an apical complex for penetrating host cell cytoplasmic membranes. Includes Plasmodium species, that cause malaria Kinetoplastids: Characterized by a complex mass of DNA in their mitochondrion. Includes Trypanosoma species, which cause sleeping sickness and Chagas' disease. Loboseans: Protists with an amoeboid shape that move by means of pseudopodia. Includes Entamoeba histolytica, which may cause dysentery

Distinguish between genotype and phenotype.

Phenotype: The organanism's observable characteristics. For example, presence of a flagellum. Genotype: The genetic makeup of the organism - in other words, the DNA sequence

Match the taxonomic principles with their definitions.

Phylogeny: Evolutionary relatedness of organisms Classification: The process of arranging organisms into similar or related groups for study Identification: The process of characterizing an isolate to determine the group to which it belongs Nomenclature: The system of assigning names to organisms.

One of the greatest causes of human deaths through time has been due to

Plasmodium spp.

The chemical nature of exotoxins is that of a

Protien

Which of the following microbes is an economically important fungus, which is also known as baker's yeast?

Saccharomyces cerevisiae

Match five methods used to characterize different strains of prokaryotes with their descriptions.

Serological Typing: This type of testing relies on the use of specific antibodies to detect unique antigens on the microbe. Phage Typing: This type of testing relies on the use of specific bacteriophages to detect a particular microbe strain. Molecular Typing: This type of testing relies on detecting specific differences in the microbe's DNA or DNA patterns Biochemical Typing: This type of testing relies on unique metabolic activities of the microbe. Antibiograms: This type of testing relies on antibiotic susceptibility patterns generated by specific microbes

Please classify the following as either a sign or a symptom.

Sign: Fever, Swelling, Rash, Pus Formation Symptom: Pain, Nausea, Malaise, Headache

Which of the following descriptions fits the definition of a viroid?

Single-stranded RNA molecules forming a closed ring

The basic taxonomic unit in the classification scheme of plants and animals is

Species

Gram-positive encapsulated diplococci found in sputum is indicative of

Streptococcus pneumoniae.

Why is it that abnormal forms of prion self-proteins can accumulate over time in the central nervous system, leading to disease?

The abnormal forms are resistant to normal cellular protease degradation

A number of viruses often include a similar set of symptoms when they cause an infectious disease state (fever, headache, fatigue, runny nose). Why would they all cause the same symptoms if they're different viruses?

The symptoms are associated with the immune system's response, NOT the molecules from the pathogens themselves. Our responses against viruses are fairly similar, regardless of virus type, so the symptoms are similar.

Which of the following statements about aflatoxins are TRUE?

They are produced by Aspergillus species. They can be found in peanuts and grains. They are possible carcinogens.

Check all the TRUE statements about fungi that ferment fruit.

They are yeasts. They are facultative anaerobes. They grow in acidic conditions. They secrete enzymes to degrade organic compounds.

Fungi are found in nearly every habitat on Earth, from environments that are very hot to very cold and even in lakes with high salt concentrations ... fungi are nearly everywhere.

True

Penicillin is an antibiotic that is produced naturally by certain fungi.

True

Plasmids often carry the information for antibiotic resistance.

True

Size and shape may allow one to differentiate between a bacterium, fungus, or protozoan.

True

The host range of a virus depends on the presence of host receptor molecules.

True

Transposons can potentially inactivate bacterial genes by "jumping" into them.

True

Transposons may leave a cell by incorporating themselves into a plasmid.

True

Please choose the statement that best describes the role of viral surface proteins or spikes.

Viral spikes provide means of attachment to host cell surface.

Very often clinically relevant information may be obtained by examining

a wet mount AND the size and shape of the organism.

Diseases of short duration frequently followed by long-term immunity are referred to as

acute infections.

A selective growth medium

allows only certain bacteria to grow.

In conjugation the donor cell is recognized by the presence of

an F plasmid

Prions are

an infectious protein.

Competent cells

are able to take up naked DNA, occur naturally, AND can be created in the laboratory.

Mycobacterium tuberculosis is one of the few species of bacteria that

are acid fast.

Influenza viruses bud from the host cell. Based on this information, the viruses most likely

are enveloped

The Ames test is useful as a rapid screening test to identify those compounds that

are mutagens

Nematodes

are roundworms AND are found in the gastrointestinal tract or the blood.

In addition to lysis, animal viruses may exit the host cell by

budding

The protein coat of a virus

called a capsid, protects the nucleic acid, AND is involved in the recognition of host cell receptors by non-enveloped viruses.

All fungi have ______ in their cell walls.

chitin

APITM, EnterotubeTM, and VitekTM are all

commercially available methods used to identify bacteria.

The transfer of vancomycin resistance from Enterococcus faecalis to Staphylococcus aureus is thought to have involved

conjugation AND transposons

Gene transfer that requires cell-to-cell contact is

conjugation.

Viruses are commonly referred to by their _________ name

disease AND species

Tapeworms

do not have a digestive system AND may be transmitted by eating undercooked meat.

E. coli 0157:H7

does not ferment sorbitol AND produces a toxin

When an enveloped virus adsorbs to the host cell with its protein spikes, the virions are taken into the cell by the process of

endocytosis

The viral envelope closely resembles the

eukaryotic cellular membrane.

In conjugation, transformation, or transduction, the recipient bacteria is most likely to accept donor DNA

from the same species of bacteria.

Cells infected with animal viruses lyse because

functions necessary for cell survival are not carried out and the cell dies

Bacteria that have properties of both the donor and recipient cells are the result of

genetic recombination.

Prokaryotic cell mutations can be observed very quickly because the prokaryotic chromosome is

haploid

Among the easiest of the mutations to isolate are those which

involve haploid chromosomes AND involve antibiotic resistance.

Replica plating

is useful for identifying auxotrophs AND uses media on which the mutant will not grow but the parental cell type will.

Consider the figure of a virus infected cell. By directing the host cell to synthesize fake MHC class I molecules, the virus is

making sure its host is not destroyed by TC cells or NK cells

Various strains of E. coli

may cause disease AND may be harmless.

Outside of living cells, viruses are

metabolically inert.

Fungi are classified according to their

method of sexual reproduction.

The terms yeast, mold, and mushrooms refers to fungal

morphology.

The source of variation among microorganisms that were once identical is

mutation.

Fungal diseases are generally referred to as

mycoses

A disease-causing microorganism or virus is referred to as a(n)

pathogen.

An infection in which the virus is continually present in the body is referred to as

persistent.

The characteristics displayed by an organism in any given environment is its

phenotype

Viroids cause disease in

plants.

Bacteria may survive phagocytosis by

preventing fusion of the lysosome with the phagosome AND lysing the phagosome

The causative agent of malaria is what type of microbe?

protozoan

Bacteria that resist killing by complement proteins are termed

serum resistant

The terms helical, icosahedral, and complex refer to

shapes of viruses.

The diploid character of eukaryotic cells may mask the appearance of a mutation since

the matching chromosome may carry the dominant gene

Direct selection involves inoculating cells onto growth media on which

the mutant but not the parental cell type will grow

Strain differences are helpful in

tracing the source of outbreaks of disease.

Retroviruses are unique in that they

use RNA as a template to make DNA

Media that changes color as a result of the biochemical activity of growing bacteria

usually contain a pH indicator in the media.