Microbiology Exam 2

Methanobrevibacter oralis is an example of which type of organism?

an archaean that takes advantage of the conditions caused by periodontal disease to grow; may or may not affect disease progression

A toga is which of the following?

an outer membrane found in a taxon within the deeply branching bacteria

Which best describes Crenarchaeota?

aquatic archaea abundant in oceans

Which best describes the class Halobacteria?

archaeans that require highly saline environments

Where is the pellicle found within a protozoan?

beneath the cell membrane

Arthropods typically serve as which mechanism of transmission for viruses?

biological vector

Reverse transcriptase is used to generate which nucleic acid from RNA?

cDNA

The organelle in protists that regulates osmolarity is known as which of the following?

contractile vacuole

Which of the following is not a structure used for locomotion by protists?

contractile vacuoles

A lichen results from the mutualistic relationship between fungi and which of the following?

cyanobacteria or algae

Fungi have an important role in nutrient cycling as which of the following?

decomposers

Viruses can be visualized using which method?

electron microscope

Which of the following best describes zooplankton?

eukaryotes that are nonphotosynthetic and motile

Cytoprocts are specialized structures that carry out which cellular process?

exocytosis

The excision of the viral genome from the host chromosome is known as which of the following?

induction

Microbial ecology is defined as the study of which of the following?

interactions between microbial populations and their environment

Which effect does tomato planta macho viroids have on the crop?

loss of chlorophyll

Which unit of length best describes the average size of a virion?

nm

Protozoa are best described as being:

nonphotosynthetic unicellular microorganisms

Transmissible spongiform encephalopathies, such as Creutzfeldt-Jakob disease, are caused by which of the following?

prion

In the lysogenic cycle of bacteriophages, the integrated phage genome is known as which of the following?

prophage

In retroviruses, the integrated phage genome is known as which of the following?

provirus

Rhodospirillum, a genus capable of fixing nitrogen, is a type of which of the following?

purple nonsulfur bacteria

The source of agar, which is typically used in the microbiology laboratory, is which of the following?

red algae

Which of the following is a novel enzyme found in retroviruses?

reverse transcriptase

Chicken pox can reemerge as which disease?

shingles

Which mechanism of horizontal gene transfer relies on the use of viruses?

transduction

The Baltimore Classification system describes viruses according to which characteristic?

viral genome

An acellular entity composed of a small circular RNA molecule without a capsid and capable of replicating its genome is known as which of the following?

viroid

Approximately what percentage of prokaryotes are thought to be pathogens?

<1%

Which of the following is the host-cell receptor that recognizes human immunodeficiency virus (HIV)?

CD4

A zoonosis can only be transmitted from animals to humans.

False

All protozoans can reproduce sexually and asexually.

False

Although Archaea cannot be classified as gram positive or gram negative, all Bacteria can be classified into one of these two categories.

False

Amoeba spp. use cilia as a means of locomotion.

False

Any virus can infect any host cell. (T/F)

False

Which method cannot be used to detect virus in a patient's serum?

Growth in a pure culture

It is an infectious cellular pathogen.Which of the following is not a property of a virus?

It is an infectious cellular pathogen.

Which scientist first discovered prions?

Stanley Prusiner

Apicomplexans are parasitic protists.

True

Most plant viruses do not kill their host.

True

Mycoplasmas are bacteria that lack cell walls.

True

Phototrophic bacteria may have carotenoids, which are the red and orange pigments also used as accessory pigments by plants.

True

African sleeping sickness is caused by which pathogen?

Trypanosoma bruceii

Cestodes are often transmitted via which of the following?

undercooked meats

What unique molecules are found in the cell wall and membrane of fungi, and serve as targets for antifungal agents? (Study question)

Animals have cholesterol in their cell membranes, while fungal cell membranes have different sterols called ergosterols. Ergosterols are often exploited as targets for antifungal agents.

Which of the following is the correct classification for the methanogens?

Archaea

How do archaea differ from bacteria?

Archaea have ether linkages in their cell membranes.

Which of the following bacterial genera is microaerophilic?

Campylobacter

Which fungus is common in the microbiota of a healthy individual?

Candida albicans

How did chloroplasts in eukaryotes arise? (Study question)

Chloroplasts in some lineages appear to have resulted from secondary endosymbiosis, in which another cell engulfed a green or red algal cell that already had a primary chloroplast within it. The engulfing cell destroyed everything except the chloroplast and possibly the cell membrane of its original cell, leaving three or four membranes around the chloroplast.

Two species of bacteria live in near each other and use similar food resources. Which type of biological interaction does this describe?

Competitive interaction

Which of the following is a phylum in Domain Archaea?

Crenarchaeotae

Describe three cytopathic effects of viruses on eukaryotic cells.

Cytopathic effects (CPEs) are distinct observable cell abnormalities due to viral infection. CPEs can include loss of adherence to the surface of the container, changes in cell shape from flat to round, and shrinkage of the nucleus.

One of the earliest truly multicellular green algae is Volvox.

False

Prion diseases cannot be transmitted from one generation to the next.

False

Spirochetes are generally easy to culture in the laboratory.

False

The bacterial species found associated with the human body are very similar from one individual to another.

False

The deeply branching bacteria contain species that have evolved most recently.

False

The feeding and growth portion of a protozoan's life cycle is known as the cyst stage.

False

The green algae that are most closely related to land plants are known as the Chlorophyta.

False

The hemagglutinin assay can only identify infectious virus particles.

False

There is a cure for transmissible spongiform encephalopathies.

False

Which of the following statements is incorrect?

Fungi can be autotrophic or heterotrophic.

The most common bacterial genus found in plaque on teeth is which of the following?

Fusobacterium

Which best describes Halobacterium salinarum?

It is one of the oldest archaea.

When there was an outbreak of mad cow disease (bovine spongiform encephalopathy) in 2003, everyone was concerned about eating certain beef products but not about eating steak. Why?

Mad cow disease is a form of transmissible spongiform encephalopathy primarily affecting cattle. It can be transmitted to humans by consumption of contaminated cattle products. Prions are known to cause various forms of transmissible spongiform encephalopathy (TSE) in human and animals. The accumulation of rogue proteins causes the brain tissue to become sponge- like, killing brain cells and forming holes in the tissue, leading to brain damage, loss of motor coordination, and dementia.

What is the role of Bacteroides in the human gut and what are the effects of antibiotic use on them?

Most Bacteroides are mutualistic. They benefit from nutrients they find in the gut, and humans benefit from their ability to prevent pathogens from colonizing the large intestine. Populations of Bacteroides are reduced in the gut when a patient takes antibiotics. The gut becomes a more favorable environment for pathogenic bacteria and fungi, which can cause secondary infections.

Which of the following cannot be classified as either gram positive or gram negative on the basis of the Gram staining protocol?

Mycoplasma

Which organism is best known as the "brain-eating amoeba"?

Naegleria fowleri

(−)ssRNA is transcribed into (+)ssRNA using which of the following?

RNA polymerase encoded by the virus

What is the difference between viroids and virusoids?

The big difference between viroids and virusoids is that virusoids cannot cause disease without a helper virus, while viroids can infect by themselves. Also, virusoids cause distinct disease from their helper virus, though typically do not affect helper virus replication.

Briefly describe the difference between the lytic and lysogenic cycles.

The difference between lysogenic and lytic cycles is that, in lysogenic cycles, the spread of the viral DNA occurs through the usual prokaryotic reproduction, whereas a lytic cycle is more immediate in that it results in many copies of the virus being created very quickly and the cell is destroyed.

A bacteriophage infects a host cell and the genome integrates itself into the host chromosome. Sometime later, the phage is excised along with a short piece of DNA adjacent to the insertion point. Both the phage DNA and the host DNA are packaged into the same capsid. The bacteriophage then infects a new cell, delivering both phage and bacterial DNA. Which process is being described in this scenario?

The lysogenic cycle, reactivating as the lytic cycle, followed by specialized transduction

Lichens attach to a surface using which structure?

Rhizines

RT-PCR relies on an enzyme encoded by retroviruses.

True

Saprozoic fungi feed on dead organisms by ingesting small soluble food particles.

True

Satellite RNAs can encode for protein.

True

The class Bacilli includes both rod-shaped and spherical bacterial species.

True

What are the four phyla of fungi that are important causes of human mycoses? (Study question)

Zygomycota, Ascomycota, Basidiomycota, and Microsporidia

Pseudopod formation requires which cytoskeletal component?

actin filaments

The human microbiome consists of which of the following?

all microbes present on or in the body

Which is the best example of a population?

all the microbes of a single species living in a particular area

Compare and contrast bacteriophages and animal viruses. In what ways are they the same and in what ways are they different?

Bacteriophages have a lytic or lysogenic cycle. Bacteriophages inject DNA into the host cell, whereas animal viruses enter by endocytosis or membrane fusion. Animal viruses can undergo latency, similar to lysogeny for a bacteriophage. During attachment, bacteriophages have protein on tails that attach to cell walls, while animal viruses have spikes, capsids, or envelope proteins that attach to cell membranes. The site of synthesis for bacteriophages is in the cytoplasm, while animal viruses have RNA viruses that are synthesized in the cytoplasm and most DNA viruses are synthesized in the nucleus.

Which of the following is a parasitic ciliate?

Balantidium coli

Most mushrooms and puffballs are members of which fungal phylum?

Basidiomycota

The liquid portion of blood that does not contain clotting factors is known as which of the following?

Serum

Define the term "tissue tropism."

Tendency of most viruses to infect only certain tissue types within a host.

From where were HeLa cells first isolated? Why are they used in virology?

The HeLa cell line was originally cultivated from tumor cells obtained from Henrietta Lacks, a patient who died of cervical cancer in 1951. Prior to the discovery of HeLa cells, scientists were not able to establish tissue cultures with any reliability or stability. More than six decades later, this cell line is still alive and being used for medical research.

What is the most potent natural carcinogen known and what organism produces it? (Study question)

The most potent natural carcinogen is aflatoxin and the fungus Aspergillus flavus produces it.

You are a nurse and you suspect that you may have been exposed to a particular virus. You and your health care provider decide to perform a hemagglutinin assay. A sample of your serum is taken and added to a sample of virus. Next, the virus and serum sample are added to erythrocytes. Upon examination, you do not see any agglutination occurring. Which can you conclude from these results?

The test result suggests you may have been exposed to the virus, and your serum contains antibodies against the virus

Describe how Trypanosoma brucei, which causes the disease known as African sleeping sickness, is transmitted to the host. (Study question)

These tropical diseases are spread by insect bites by tsetse flies. In African sleeping sickness, T. brucei colonizes the blood and the brain after being transmitted.

How do cyanobacteria obtain energy? (Study Question)

They commonly obtain their energy through oxygenic photosynthesis.

Which of the following correctly describes the metabolism of methanogens?

They produce CH4.

Which best describes the metabolic activities of purple sulfur bacteria?

They use light energy to oxidize hydrogen sulfide, producing sulfur and sulfuric acid.

(+)ssRNA can be directly used in translation at the ribosome.

True

All the bacteria classified within the genus Bacillus are capable of forming endospores.

True

Conidia are asexual fungal spores produced by members of the Ascomycota.

True