What is a bacterial colony?
A visible mass of millions of bacterial cells
What does each individual colony represent?
The progeny of a single cell
Which characteristic is NOT used to describe bacterial colonies?
Genetic material
Why is colony morphology important in bacterial identification?
It is genetically determined and helps differentiate species
What is the significance of producing isolated colonies in bacterial identification?
It ensures the purity of the culture for accurate identification
Which of the following is a characteristic used to describe bacterial colonies?
Odor
What does the term 'pure culture' refer to in microbiology?
A culture containing only one species or strain of bacteria
What does the appearance of bacterial colonies depend on?
The species or strain of bacteria and substances they produce
What is the primary function of flagella in bacteria?
Motility
Which flagellar arrangement describes a single flagellum at one pole of the cell?
Monotrichous
What is the main challenge of using transmission electron microscopy to observe flagella?
It is costly and technically challenging
- What is Brownian motion?
Random movement of particles due to collisions with atoms or molecules
- What is the purpose of using a motility medium?
To confirm true motility
14. What is the concentration of agar used in a semi-solid motility medium?
0.5%
- Why is triphenyltetrazolium chloride (TTC) added to the motility medium?
To act as an electron acceptor and indicate bacterial presence
- What color does TTC turn when reduced by bacteria?
Red
What is the purpose of using a concave slide in a wet-mount preparation?
To observe motile organisms directly
- What is the term for a cell covered in flagella?
Peritrichous
- What is the term used to describe very small bacterial colonies?
Pinpoint
- Which tool is recommended for observing the general appearance of a typical colony?
Dissecting scope
- What characteristic describes the edge of a bacterial colony?
B) Margin
- How is the elevation of a bacterial colony observed?
B) From the side of the plate
23. What does it mean if a colony is described as opaque?
It blocks most of the light
24. What indicates that bacteria produce an intracellular pigment?
The colony becomes colored
- What is the term for colonies that take on the color of the straw-colored
media?
B) Nonpigmented
26. Why should the plate be placed in an inverted position during incubation?
D) To prevent condensation from dripping onto the colonies
27. What causes microbial colonies to be colored?
C) Both intracellular and extracellular pigments
28. What happens to the media if the organism produces an extracellular pigment?
B) The media becomes colored
29. Which of the following describes the different degrees of opacity in microbial colonies?
A) Transparent, translucent, opaque
30. Why is it preferable to mark the bottom of the Petri dish rather than the top?
B) To ensure the markings are not erased during incubation
31. Why must you flame the loop in between each set of streaks?
A) To sterilize the loop and prevent cross-contamination
32. What is the common method used to isolate organisms in microbiology?
B) Spread plate method
33. Why should you “drag” organisms from the previous streak section for only part of the streaking of the next section?
B) To create a dilution gradient and isolate individual colonies
34. What is the purpose of using a broth culture as inoculum in the
streak plate
method?
B) To ensure a uniform distribution of bacteria
35. What is the recommended incubation temperature for the streak plate method?
C) 37°C
36. Why is it important to use sterile technique when obtaining organisms from broth or solid medium?
B) To prevent contamination
37. What is the ideal characteristic of an antimicrobial drug?
A) It kills the harmful organism without damaging the host
- Why might the susceptibility of a pathogen to a specific antibiotic change during therapy?
B) Due to the development of antibiotic resistance
39. What was the purpose of the earliest methods of utilizing agar media in the 1940s?
B) To determine the minimum inhibitory concentration (MIC) of antimicrobial agents
40. What is the Kirby-Bauer method also known as?
B) Disk diffusion method
41. What does a clear zone around a disk in the Kirby-Bauer method indicate?
B) The absence of bacterial growth
42. What factors determine the size of the zone of inhibition in the Kirby-Bauer method?
B) The relative susceptibility of the microbe and the diffusion rate of the chemical
43. What are the possible results reported in the Kirby-Bauer method?
B) Sensitive, intermediate, or resistant
44. Why are antibiotics not effective against viruses?
B) Antibiotics target bacterial structures and functions, not viral ones
45. What type of radiation is ultraviolet radiation classified as?
B) Non-ionizing radiation
46. What type of damage does ultraviolet radiation cause to DNA?
B) Formation of pyrimidine dimers
47. Which nitrogenous bases are typically involved in the formation of pyrimidine dimers due to UV radiation?
D) Thymine and thymine
48. What is the wavelength range of UV-C radiation used in Ultraviolet Growth Inhibition (UVGI)?
A) 100 to 280 nm
49. What is the primary effect of UV-C radiation on bacteria?
B) It causes mutations or cell death
50. Why is UV-C radiation considered to have maximum germicidal effect?
C) It has the shortest wavelength and highest energy
51. What is the main application of Ultraviolet Growth Inhibition (UVGI)?
B) Sterilizing medical instruments and surfaces
52. What is a potential health risk of exposure to UV-C radiation for humans?
A) Increased risk of skin cancer
53. What is one way microorganisms adjust their environment to survive?
By changing the temperature or pH of the environment
54. What is a side effect of bacterial metabolism and infection?
Disease
55. What is the primary difference between Gram-positive and Gram-negative bacteria?
Gram-positive bacteria have a thick layer of peptidoglycan within their cell wall
56. What is the Enterotube II system specifically used for?
Identifying bacterial enzymes and fermentations
57. How do commercial rapid diagnostic kits, like the Enterotube II system, benefit laboratory technicians?
They save money, effort, and critical diagnostic time
58. Which growth pattern is characterized by bacteria floating on the top of the broth due to a waxy cell wall or gas vacuole?
. Pellicle
59. What can cause changes in the expected growth patterns of bacteria in broth?
Differences in incubation conditions such as time, temperature, pH, and nutrient composition
60. What is the term for the growth pattern where bacteria form clumps or aggregates throughout the broth?
. Flocculent
61. Which factor is NOT mentioned as potentially altering bacterial growth patterns in broth?
The type of Petri dish used
62. What is the significance of colony morphology in identifying unknown bacteria?
It helps differentiate between bacteria based on their growth patterns
63. What are the two purposes of the enzyme urease in bacteria?
Neutralizing acidic environments and providing nitrogen for protein synthesis
64. Which of the following is NOT a component of Rustigian and Stuart’s Urea broth?
. Dextrose
65. What color change indicates a urease-positive organism in the urea broth?
Pink to orange
66. What is the purpose of the Durham tube in the phenol red experiment?
To collect gases formed as by-products of sugar fermentation
67. What color change indicates acid production in the phenol red experiment?
Red to yellow or orange
68. What is the primary purpose of Fluid Thioglycollate (FTG) medium?
To determine whether a bacterium is an aerobe or an anaerobe
69. What role does resazurin play in the FTG medium?
It acts as an indicator of oxidation-reduction
70. Where in the FTG medium would you expect to find obligate anaerobes growing?
At the bottom of the tube
71. What is the function of catalase in bacteria?
To neutralize hydrogen peroxide by degrading it into water and oxygen
72. Which of the following bacteria are catalase positive?
Staphylococcal spp
73. What indicates a positive catalase test result?
Formation of bubbles
74. What is the role of cytochrome c oxidase in the electron transport chain (ETC)?
To donate electrons to oxygen to form water
75. Which reagent is used in the oxidase test to identify cytochrome c oxidase–positive organisms?
Tetramethyl-p-phenylene diamine
76. What color change indicates a positive result in the oxidase test?
Dark blue/purple
77. What enzyme do Proteus and Providencia species produce that removes the amine group from phenylalanine?
. Phenylalanine deaminase
78. What color change indicates a positive result for phenylalanine deaminase activity?
. Yellow to green
79. What is the purpose of the 12% ferric chloride (FeCl3) reagent in the phenylalanine deaminase test?
To react with keto-acids like phenylpyruvic acid to produce a green color
80. What is the role of lipase in bacteria?
To hydrolyze lipids into smaller subunits
81. What indicates lipolytic activity in a lipase-positive organism on tributyrin agar?
. A clearing or dark halo around the bacterial growth
82. Which of the following is NOT a component of the media used for testing lipolytic activity?
. Glucose
83. What does SIM stand for in the context of microbiological testing?
. Sulfur, indole, and motility
84. What is the purpose of sodium thiosulfate in SIM media?
To act as a sulfur source
85. Why is SIM medium considered a combination differential media?
It tests for multiple biochemical features specific to Enterobacteriaceae family members
86. What is the purpose of the MR-VP broth in glucose fermentation testing?
To test for the pathway used to ferment glucose
87. Which fermentation pathway is detected by the Voges-Proskauer test?
. Butanediol fermentation
88. What is the pH range at which methyl red changes color to indicate a positive result for mixed acid fermentation?
Below 4.5
89. Which of the following is NOT a product of the mixed acid fermentation pathway?
. 2,3-butanediol
90. What does the Voges-Proskauer test detect in glucose fermentation?
The production of acetoin and 2,3-butanediol
91. What is the sole carbon source in Simmon’s citrate medium?
. Sodium citrate
92. What color change indicates a positive result for citrate utilization in Simmon’s citrate medium?
Green to blue
93. What compound is formed in the medium as a result of citrate hydrolysis and subsequent reactions?
. Sodium carbonate
94. What is the purpose of cooling the gelatin medium to below 25°C after incubation?
To solidify the gelatin if it is still present
95. What indicates a positive result for gelatinase activity in the gelatin medium?
The medium remains liquid after cooling
96. What does the enzyme gelatinase hydrolyze gelatin into?
. Peptides and amino acids
97. What are the two glucose polymers that make up a molecule of starch
Amylose and amylopectin
98. What indicates a positive starch test when iodine is added to the medium?
A colorless (golden) halo around the bacterial growth
99. What is the role of the enzyme amylase in bacteria?
To hydrolyze starch into smaller molecules like dextrins, maltose, and glucose
100. How do nonmotile bacteria grow in the motility test medium?
They grow along the stab line
101. What color change occurs in the motility test medium when triphenyltetrazolium chloride (TTC) is reduced by bacterial metabolism?
Colorless to red
102. What is the primary by-product of sucrose fermentation by Streptococcus species in the oral cavity?
Dextran
103. What role does dextran play in the formation of dental caries?
. It forms a biofilm that helps retain organic acids on the tooth surface
104. Why is effective brushing and flossing important in preventing dental caries?
It removes plaque, which contains the biofilm and bacteria
105. What factors determine the specificity of normal microbial flora in different locations within the body?
Oxygen concentration, pH, moisture, and types of secretions
106. What indicates alpha hemolysis on blood agar plates (BAPs)?
A greening of the plate around the colony
107. Which type of agar plate is used for the isolation and differentiation of Staphylococci?
Mannitol salt agar plates
108. How are the four major classes of the phylum Protozoa distinguished?
By their locomotor or reproductive structures
109. What are the two primary forms of amoeba found in their host?
Trophozoites and cysts
- Where are trophozoites usually found in the host?
. In fresh diarrheal stools
111. Which characteristic is diagnostic for the trophozoite of E. histolytica?
Ingested red blood cells (RBCs)
112. How is the cyst of E. coli distinguished from that of E. histolytica?
. Presence of eight nuclei with short chromatoid bodies
113. Which organism does not form cysts and has a trophozoite with one or two nuclei arranged at opposite ends of the cell?
. D. fragilis
114. Which characteristic is unique to the trophozoite of C. mesnili?
. Bilaterally symmetrical with two sucking disks
115. How can the cyst of G. lamblia be described?
Lemon-shaped with a protrusion at the anterior end
116. Which organism is found only as a feeding trophozoite and has no cyst stage?
. T. hominis
117. What are the two large groups of helminths?
. Trematodes and nematodes
118. How are tapeworms (cestodes) different from flukes (trematodes)?
Tapeworms are segmented, while flukes are not segmented
119. What is a proglottid in the context of tapeworms?
. A segment containing male and female sexual organs
120. What are the three different organisms in the Fungus group mentioned in the text?
Mushrooms, molds, and yeasts
121. How are molds in the Fungi Imperfecti group identified?
By their method of spore formation
122. Which fungal group includes the common yeast used in bread baking and beer production?
Ascomycetes
123. What is the primary difference between fungal and plant cell walls?
Fungal cell walls are composed of chitin, while plant cell walls are composed of cellulose.
124. Which type of fungal spore is formed within a sac called a sporangium?
Sporangiospores
125. What role do vegetative hyphae play in molds?
They anchor the fungus and absorb nutrients
126. What is the primary function of hyphae in mycelial fungi?
To absorb food after decomposing it with enzymes
127. Which phylum of fungi is responsible for producing most mushrooms?
Basidiomycota
128. What is a notable feature of fungi compared to most bacteria?
. Fungi can reproduce both asexually and sexually
129. Why is the Zygomycota group no longer considered an official phylum by fungal taxonomists?
They are not an evolutionarily unified group
130. What type of symbiotic relationship do lichens represent?
Mutualistic
131. What is a key feature of ectomycorrhizal fungi?
They are found on the roots of conifers and other woody plants
132. What is a key difference between yeast fungi and mycelial fungi?
. Yeast fungi are unicellular, while mycelial fungi are multicellular.
133. Which mechanism is the most common for asexual reproduction in yeasts?
Budding
134. What role does S. cerevisiae play in human activities?
It is used in baking and alcoholic beverage production
135. What is the dormant, nonmotile stage in the life cycle of Protozoa called?
. Cyst
136. Which group of organisms includes mosquitoes, ticks, lice, bed bugs, and fleas?
Arthropods
137. What is the primary characteristic of algae that differentiates them from Protozoa?
Algae contain cellulose and pectin in their cell walls
138. What is the primary function of the pellicule in protozoa?
To protect the cell and assist in food ingestion
139. How are medically important Helminthes classified?
By their phyla: Platyhelminthes and Nematoda
140. What is a characteristic feature of flatworms in the phylum Platyhelminthes?
They absorb food directly across a nonliving covering called a cuticle
141. How do members of the Mastigophora move?
By using flagella
142. What is a characteristic feature of organisms classified as Ciliophora?
. They use cilia for movement and feeding.
143. Which organism is the agent of toxoplasmosis?
. Toxoplasma gondii
144. What is the primary characteristic of the Apicomplexa (Sporozoa)?
They have a complex life cycle and are all parasites
145. Which organism is observed in a blood smear from a patient with malaria?
. Plasmodium falciparum
146. What is the shape of the nucleus in Stentor?
Resembling a string of beads
147. What type of motility do members of Sarcodina (amoeba and related organisms) use?
Pseudopodia
148. Which organism is associated with the sexually transmitted disease trichomoniasis?
. Trichomonas vaginalis
149. What is the function of the contractile vacuoles in Paramecium?
Regulation of osmotic balance
150. Who discovered the ABO blood group system?
Karl Landsteiner
151. What antigens are present on the red blood cells of a person with type AB blood?
Both A and B antigens
152. Which blood type has antibodies against both A and B antigens in
their plasma?
A. Type A
Type O
153. What happens during a Type II cytotoxic reaction in an incompatible blood transfusion?
The recipient’s antibodies react with the donor’s RBC antigens
154. What is the Rh factor?
An antigen found on RBCs
155. What can happen if an Rh− mother becomes sensitized to Rh+ blood and conceives a second Rh+ child?
The mother’s antibodies may attack the child’s RBCs
156. What is hemolytic disease of the newborn (HDNB)?
A condition where the mother’s antibodies attack the child’s RBCs
157. Why are individuals with type O blood called “universal donors”?
They have neither A nor B antigens
158. Why are individuals with type AB blood called “universal recipients”?
They can receive blood from any donor without adverse reactions
159. What triggers the production of antibodies against Rh factor in an Rh− person?
Exposure to Rh+ blood