Exam 1 - (CH 1) Bacterial Cell Structure, Physiology, Metabolism, and Genetics Textbook Review Questions

Question 1

Dimorphic fungi characteristically grow in this phase at 37°C.
A. Filamentous
B. Yeast
C. Syncytial
D. Mycelial

Answer 1

B. Yeast

Question 2

A virus that infects and possibly destroys bacterial cells is called a(n)
A. virion.
B. biovar.
C. bacteriophage.
D. archaebacteria.

Answer 2

C. bacteriophage.

Question 3

A unique gram-positive bacteria cell wall component that is anchored to the peptidoglycan layer is called
A. teichoic acid.
B. lipoteichoic acid.
C. N-acetyl-d-glucosamine.
D. endotoxin.

Answer 3

A. teichoic acid.

Question 4

This portion of the lipopolysaccharide layer is responsible for producing fever and shock conditions in patients infected with gram-negative bacteria.
A. Periplasmic space
B. O-specific polysaccharide
C. N-Acetyl-d-muramic acid
D. Lipid A

Answer 4

D. Lipid A

Question 5

Which cytoplasmic structure is the site for rRNA synthesis?
A. Histone
B. Rough endoplasmic reticulum
C. Golgi apparatus
D. Nucleolus

Answer 5

D. Nucleolus

Question 6

Which of the following describes a fusiform shape?

A. Tapered, with pointed ends
B. Curved
C. Swollen, with rounded ends
D. Helical

Answer 6

A. Tapered, with pointed ends

Question 7

Fifty percent of the dry weight of bacteria are composed of this essential element for bacterial growth.
A. Nitrogen
B. Carbon
C. ATP
D. Potassium

Answer 7

B. Carbon

Question 8

Media containing additives that inhibit the growth of some bacteria but allow other to grow are called
A. nutrient.
B. selective.
C. differential.
D. transport.

Answer 8

B. selective.

Question 9

Cells that take up naked DNA are referred to as
A. competent.
B. clones.
C. homologous.
D. transduced.

Answer 9

A. competent.

Question 10

The transfer of genetic material from a donor bacterial strain to a recipient strain is called
A. lysogeny.
B. transformation.
C. transduction.
D. conjugation.

Answer 10

D. conjugation.

Question 11

Explain the reason why the laboratory scientist in the Case in Point should repeat the Gram stain procedure on the exudate.

Case in Point
A 4-year-old girl presents with symptoms of redness, burning, and light sensitivity in both eyes. She also complained of her eyelids sticking together because of exudative discharge. A Gram stain of the conjunctival exudates (product of acute inflammation with white blood cells and fluid) showed gram-positive intracellular and extracellular, faint-staining, coccobacillary bacteria. The organisms appeared to have small, clear, nonstaining “halos” surrounding each cell. This clear area was noted to be between the stained organism and the amorphous (no definite form; shapeless) background material. The Gram stain of the quality control organisms Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) revealed gram-positive reactions for both organisms.

Answer 11

The Gram stain needs to be repeated because the E. coli quality control slide gave a false gram-positive reaction. Because of this quality control result, the smear made from the clinical sample could not be accurately interpreted.

Question 12

What might have occurred to make the Gram stain results invalid?

Case in Point
A 4-year-old girl presents with symptoms of redness, burning, and light sensitivity in both eyes. She also complained of her eyelids sticking together because of exudative discharge. A Gram stain of the conjunctival exudates (product of acute inflammation with white blood cells and fluid) showed gram-positive intracellular and extracellular, faint-staining, coccobacillary bacteria. The organisms appeared to have small, clear, nonstaining “halos” surrounding each cell. This clear area was noted to be between the stained organism and the amorphous (no definite form; shapeless) background material. The Gram stain of the quality control organisms Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) revealed gram-positive reactions for both organisms.

Answer 12

The most likely cause of the false gram-positive result for E. coli was insufficient decolorization time. Crystal violet, the primary stain, was not removed from the bacterial cells.

Question 13

Differentiate the role of pili from the role of flagella.

Answer 13

Pili, made up of pilin protein, aid in bacterial attachment to solid surfaces such as mucous membranes. Flagella, consisting of flagellin protein, are responsible for motility.

Question 14

What is the role of the capsule in the pathogenesis of infectious diseases?

Answer 14

Capsules help microorganisms resist phagocytosis. Phagocytic cells are less able to bind to the capsular polysaccharide than they are to surface proteins. In addition, capsules hide antigens on the surface of bacteria, preventing them from interacting with antibodies produced by an animal in response to an infection.

Question 15

Why is lipopolysaccharide (LPS) a significant outer-membrane structure in gram-negative bacteria?

Answer 15

LPS is also known as endotoxin. This molecule is toxic to animals, inducing nonspecific effects such as fever, inflammation, hypotension, and shock. LPS contains three regions: an antigenic O– specific polysaccharide, a core polysaccharide, and an inner lipid A. The lipid A moiety is responsible for producing fever and shock conditions in patients infected with gram-negative bacteria.

Question 16

A bacterium that grows only on plates incubated in the absence of oxygen would be categorized as a( n):

a. Aerotolerant anaerobe.
b. Facultative anaerobe.
c. Obligate anaerobe.
d. Obligate aerobe.

Answer 16

c. Obligate anaerobe.

Question 17

Fimbriae present on the outer surface of bacteria are used for:

a. Adherence to surfaces.
b. Antimicrobial resistance.
c. Sexual reproduction.
d. Bacterial motility.

Answer 17

a. Adherence to surfaces.

Question 18

All of the following are characteristic of fermentation except:

a. It begins with the breakdown of pyruvic acid.
b. It follows glycolysis and produces reduced nicotinamide adenine dinucleotide (NADH).
c. It produces acids, alcohols, and gases.
d. It can occur in the presence of oxygen.

Answer 18

b. It follows glycolysis and produces reduced nicotinamide adenine dinucleotide (NADH).

Question 19

Why are older bacterial cells more easily decolorized than cells from younger colonies?

Answer 19

Older bacterial cells are decolorized more easily than younger cells, because as cells age their cell walls become “leaky” and allow molecules to pass more readily out of the cell. In the Gram stain, the crystal violet– iodine complex is more readily lost during the decolorization step.

Question 20

Why are spore-forming organisms more resistant than non– spore-forming species?

Answer 20

Bacterial spores have a thick protein coat that makes them highly resistant to chemical agents, temperature changes, dehydration, ultraviolet and gamma radiation, and desiccation. They are also metabolically inactive and can therefore survive periods of starvation.

Question 21

Explain the three ways in which genetic material can be transferred from one bacterium to another.

Answer 21

The three ways in which genetic material may be transferred from one bacterium to another are transformation, transduction, and conjugation. Transformation is the uptake and incorporation of naked or free DNA into a bacterial cell. Transduction is the transfer of bacterial genes by a bacteriophage from one cell to another. Conjugation is the transfer of genetic material from a donor bacterial strain to a recipient strain. Conjugation requires close contact between the two cells.

Question 22

For the following DNA, write the complementary sequence. Include labeling the 3′ and 5′ end. 3′ TTACGGACAAC 5′: ________________.

Answer 22

3′ TTACGGACAAC 5′
5′ AATGCCTGTTG 3′

Question 23

In RNA, thymine is replaced by ________________.

Answer 23

Uracil

Question 24

In bacteriophage, how does lysogeny differ from the lytic cycle?

Answer 24

During lysogeny, phage DNA is inserted into the bacterial genome, but virus particles are not produced. When the bacterial cell replicates, the viral genome is copied along with the bacterial chromosome. During the lytic cycle, bacteriophages are produced until the bacterial cell dies and is lysed.

Question 25

Points to Remember

Answer 25

■ Many microorganisms inhabit our environment, most are nonpathogenic.
■ Prokaryotes, such as bacteria, do not have membrane-enclosed nuclei and organelles.
■ Eukaryotes differ from prokaryotes in that they have membrane-enclosed nuclei and organelles.
■ Viruses cannot be seen under an ordinary light microscope, although their cytopathic effects on cell lines are visible. They are obligate parasites, and antibiotics are ineffective for treatment of viral infections. Viruses have DNA or RNA, but rarely both, in contrast to prokaryotes and eukaryotes.
■ A major way bacteria are classified in the diagnostic microbiology laboratory is by the Gram stain reaction. Whether an organism is gram-positive (blue or purple) or gram-negative (pink or red) is an important first step in identifying bacteria and in determining appropriate antimicrobial therapy.
■ Bacterial spores are formed as a result of harsh environments. They are a means of survival, not reproduction.
■ The LPS contained in the outer membrane of gram-negative bacteria consists of three regions: an antigenic O– specific polysaccharide, a corepolysaccharide, and an inner lipid A (also called endotoxin). The lipid A moiety is responsible for producing fever and shock conditions in patients infected with gram-negative bacteria.
■ Bacteria utilize two biochemical pathways, fermentation and respiration, to catabolize carbohydrates to produce energy