MCB 100 Exam 2

The ________ are the largest known group of archaea.

methanogens

In which of the following methods of prokaryotic reproduction does the parental cell remain intact after the reproduction event to continue the process?

budding

Which of the following is NOT a typical habitat for an extremophile?

the bottom of a swamp

What type of arrangement occurs when bacilli divide by snapping division?

Palisades and V-shapes

Submit

Endospores

may be produced when nutrients are scarce.

The most common form of reproduction among prokaryotes is (budding/binary fission/snapping division).

binary fission

A bacterial species with spherical cells that have random planes of cell division will form which of the following arrangements?

staphylococci

What are flexible, spiral-shaped bacteria called?

spirochetes

The majority of prokaryotes are capable of forming endospores.

false

Rhizobium is important agriculturally because it supplies __________ to plants such as peas and beans.

fixed nitrogen

Halophiles grow equally well in the presence or absence of high salt concentrations.

false

Which of the following is NOT a property of Lactobacilli?

They are members of the high G + C Gram-positive bacteria.

What type of arrangement forms when multiple planes of division occur randomly in cocci?

Staphylococci

Which of the following characteristics distinguish the archaea from the bacteria?

cell wall composition, cytoplasmic membrane lipids, and rRNA sequences

Which of the following is CORRECT about the prokaryotes known as deeply branching bacteria?

They are commonly found in acidic, anaerobic conditions.

In which of these ways do archaea differ from bacteria?

Archaea lack peptidoglycan in their cell walls.

Which of the following correctly describes the function of bacterial endospores?

Endospores are produced as resting stages of the bacterium that can survive inhospitable conditions.

Are Clostridium botulinum vegetative cells required to be present for foodborne botulism to occur?

No, foodborne botulism is caused by the botulinum toxin produced by the bacteria, not the bacteria themselves.

How are patients typically infected with listeriosis?

Contaminated food or drink

How might an infected patient transmit listeriosis to another human?

During pregnancy.

What is listeriolysin O?

An enzyme breaks the bacteria free from the phagosome.

The polymerization of actin filaments allows Listeria to form pseudopods extending from the host cell. How does this aid the bacteria during infection?

They are able to spread to neighboring cells sheltered from detection by the host immune system.

To diagnose meningitis due to Listeria infection, physicians will first examine a patient's ___.

cerebrospinal fluid

If ampicillin is the prescribed treatment for listeriosis, why might a physician instead prescribe trimethoprim-sulfamethoxazole?

Patients may be allergic to penicillins.

Which of the following habits will best prevent infection due to listerosis?

Avoid eating raw fruits and vegetables

Considering the fact that Pseudomonas aeruginosa has so many virulence factors, why is it not a more common source of infection in the general public, rather than only an opportunistic pathogen?

P. aeruginosa cannot penetrate the skin and mucous membranes or evade the body's other defenses.

Which of the following is an effective way to prevent many staphylococcal infections?

proper cleansing of wounds

Which virulence factor allows Staphylococcus aureus to escape fibrin clots to spread to new locations in the body?

Staphylokinase

What is the characteristic sign of pertussis?

Paroxysmal cough

How does streptokinase facilitate virulence of Streptococcus pyogenes?

By breaking down blood clots, facilitating the spread of S. pyogenes through infected and damaged tissues.

Mycobacterium tuberculosis is considered a(n) __________.

aerobe

One of the primary reasons the disease is able to evade the body's immunity is that it __________.

resists digestion by phagocytes

In approximately 10% of patients tubercles rupture and reactivate infection. This is known as _____ tuberculosis.

secondary

It is estimated that _____ of the world's population may be infected with tuberculosis.

33%

How do clinicians primarily screen for tuberculosis in patients?

Tuberculin skin test

Why does tuberculosis involve months of antibiotic treatment?

The bacteria grow very slowly.

What is the name of the vaccine given to prevent TB in countries where it is endemic?

BCG vaccine

What is the difference between the cell walls of Gram-positive bacteria and those of Gram-negative bacteria?

A Gram-positive bacterium has a thick layer of peptidoglycan and lacks an outer membrane.

What is the difference between Gram-positive bacteria and mycoplasmas?

Gram-positive bacteria have thick cell walls, while mycoplasmas lack cell walls.

What is the function of endospores?

Endospores are survival structures.

How does coagulase facilitate bacterial virulence?

Bacteria can hide in the protein clots that result from the action of coagulase.

Members of the Enterobactericeae produce siderophores. What function do siderophores perform?

They facilitate bacterial replication by obtaining iron from host cells.

Over 90% of urinary tract infections (UTIs) are caused by Escherichia coli strains. UTIs are 14 times more common in women than in men. Why do you think this is?

UTIs caused by E. coli are 14 times more common in women than in men because women have a shorter urethra than men and the proximity of the urethra to the anus is much closer in women.

MDR-TB strains are resistant to which drugs at a minimum?

Isoniazid and rifampin

Bacteria are grouped into two categories reflecting structural features of their cells. Bacteria are classified as Gram-positive or Gram-negative based on whether or not they retain the crystal violet dye used in the Gram stain procedure. Cell wall structure determines the ability to retain the dye, thus cell wall structure is the basis of categorization into Gram-positive (G+) and Gram-negative (G-).

Which of the following occurs only in Gram-negative bacteria?

Lipopolysaccharide

Various types of damage can lead to acute inflammation, including cuts and abrasions, heat, and microbial damage. Some microbes have structures which can trigger the acute inflammatory response when they invade tissues.

What structural characteristics common to Gram-negative bacteria may trigger the acute inflammatory response?

External polysaccharides

Lipid A

The ability to produce (hyaluronidase/lipase/proteases) enables Staphylococcus aureus to penetrate and spread through tissues.

hyaluronidase

Systemic infections with fungus are difficult to treat because fungi are metabolically similar to humans, so antifungal therapies are sometimes complicated by side effects.

True

What is the main advantage of fungistatic drugs over fungicidal drugs?

They are less toxic than fungicidal drugs.

Factors that contribute to difficulty in eliminating fungal infections via the body's defenses include

both resistance to phagocytosis and cell mediated immunity.

The "gold standard" of antifungal drugs is amphotericin B. What is its target?

It targets ergosterol in the fungal cell membrane.

What does it mean for a cell to be haploid?

The cell has only one set of chromosomes.

A dikaryon differs from a diploid cell in that the dikaryon _____.

has two separate nuclei

Which stage of sexual reproduction involves the fusion of hyphae tips from opposite mating types to produce cells with two separate nuclei?

the dikaryotic stage

Fungi exist as either unicellular yeasts or _____.

filamentous molds

A mushroom is an example of _____, which is the reproductive organ of a mold.

a fruiting body

If the hyphae of a fungus are septate, this means they _____.

have crosswalls separating the cells

Diploid cells undergo meiosis producing _____.

four haploid nuclei

Sexual reproduction often involves two haploid sex cells or gametes. A smaller, mobile, male gamete typically fuses with a larger, nonmobile, female gamete. Why are the sex cells of fungi called + and -, instead of male and female?

The haploid sex cells of fungi are virtually indistinguishable from one another.

A microbiologist is making agar plates in which to grow bacteria. She can get the agar from

red algae.

Some scientists want to study cellullar interactions in colonial organisms; they could use ___________ as a research organism.

colonial algae

Which of the following is multicellular, chemoheterotrophic, and has a cell wall?

Histoplasma

Unicellular, spherical fungi are called

yeasts

The cell membranes of fungi contain (cholesterol/ergosterol/fatty acid) which is a target of some antifungal treatments.

ergosterol

Which opportunistic fungus causes thrush?

Candida albicans

What antifungal drug is commonly used to treat systemic mycoses of pathogenic fungi?

amphotericin B

Fungi that cause disease only in people with poor immunity or disrupted microbiomes are called

opportunistic fungi.

What is the most common portal of infection for true fungal pathogens that cause systemic mycoses?

inhalation

Which opportunistic fungus is characterized by pseudohyphae?

Candida

Most fungi exist as (parasites/saprobes/autotrophs) and function as the major decomposers of organic material.

saprobes

In which part of the body would candidiasis present as curd-like?

vagina

What percent of people harbor Candida naturally in their body without showing any signs or symptoms?

40-80%

Which structure is characteristic of Candida?

pseudohyphae

In which population might we observe a higher incidence of thrush?

the elderly

Which of the following habits might best prevent infection with Candida?

Change wet diapers often.

Which of the following medications is typically used for superficial candidiasis in AIDS patients?

fluconazole

A _____ is a partnership between two fungal organisms and a photosynthetic partner, such as cyanobacteria or algae.

lichen

Which of the following statements about Candida is FALSE?

It is easily treated with topical antifungals in immunocompromised patients.

How are fungal and animal cytoplasmic membranes different from each other?

Fungal cytoplasmic membranes contain ergosterol, while animal cytoplasmic membranes contain cholesterol.

What is the difference between fungal spores and bacterial endospores?

Fungal spores are reproductive structures, while bacterial endospores are survival structures.

When viewed through a microscope, some fungi with branched hyphae look somewhat like plants. Why are fungi not plants?

They lack chloroplasts and therefore cannot perform photosynthesis.

What are dimorphic fungi?

Fungi that can exist in yeast form and mold form

Fungi reproduce only asexually.

False

Most viruses cannot be seen by light microscopy.

True

Why is there an influenza epidemic about every 10 years?

Antigenic shift causes major changes in the surface antigens of influenza A viruses.

Contact between a phage and its bacterial host occurs by _____.

a random collision

What portion of bacteriophage T4 enters E. coli?

Only the T4 genome enters the bacterial cell.

Once entry into the bacterial cell has been achieved, the next step in a lytic replication cycle is _____.

synthesis

During a lytic replication cycle, what action does a phage take to ensure that its host bacterium does NOT continue synthesizing cellular molecules?

Phage enzymes degrade the bacterial DNA.

In a lytic cycle of replication, release of phages involves _____.

the bacterial cell bursting open

A major difference between the lytic and lysogenic cycles of phage replication is that during the lysogenic phase _____.

the phage genome inserts itself into the host genome

What factor may induce a prophage to enter the lytic cycle?

UV light

During the lysogenic cycle, it is possible for integrated phage genes to change the characteristics of the host cell. This is known as _____.

lysogenic conversion

HIV attaches to T-cell and macrophages by means of an interaction between gp120 and a(n) (antibody/CD4/gp41) receptor.

CD4

How is latency of animal viruses different from lysogeny of phages?

Animal viruses are not induced or excised from the host's DNA.

In a plaque assay, a microbiologist counts 20 plaques on a plate. How many plaque-forming units can be assumed to have been present in the original bacterium-virus mixture on the plate if there was no dilution of the mixture prior to plating?

20

Lysogenic viral DNA which has integrated into the host genome is referred to as

a prophage.

Which of the following events might trigger induction of a temperate bacteriophage?

exposure to UV light

How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?

The host cell dies during the lytic stage.

What is the fate of the prophage during the lysogenic stage?

It is copied every time the host DNA replicates.