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Microbiology 211 Quiz Questions, Final study
guide micro 2025 LATEST EXAM
If the anticodon is UAU, the following amino acid will be attached to this tRNA.
Isoleucine
Which of the following does apply to sigma?
a. enhances binding of RNA polymerase to promoter
Which part of DNA is continuously elongated during DNA synthesis?
b. leading strand
Carbapenam resistant Enterobacteriaceae (CRE) include strains of E. coli and Klebsiella which are responsible for a 50% mortalilty rate in infected individuals, and are most commonly acquired in a hospital environment.
True
Which one of the following statements is true?
e. DNA and RNA are composed of nucleotides
Which of the following is true about RNA Polymerase?
a. polymerizes ribonucleotides in a 5' to 3' direction during RNA synthesis.
Bacterium X is inoculated into TSB broth containing 0,3,8,12, or 15% NaCl. Following incubation, growth occurred in all tubes except for the 12% and the 15%. One drop of culture was taken from the 12% TSB broth and added to another TSB broth containing no NaCl. After incubation, no growth was found in this tube. One can conclude that NaCl is bacteriocidal for Bacterium X.
True
The diversity of the human GI microbiome decreases in many ICU patients
True
RNA polymerase would make what RNA sequence from the DNA sequence below? Read from left to right on the appropriate strand. 5'-TTGGCAA-3' 3'-AACCGTT-5'
a. 5'-UUGGCAA-3'
True/False In bacteria, gyrase acts to release the resulting positive supercoiling tension from the replication fork as it proceeds and gyrase is inhibited by ciprofloxacin
True
Which of the following is a positive test for the enzyme catalase?
c. Production of bubbles when the organism is added to hydrogen peroxide.
Which one of the following statements is true?
c. DNA and RNA sugar phosphate backbones contain phosphodiester bonds
Which one of the following DOES NOT apply to exponential ( logarithmic) growth?
c. Rate of increase in cell numbers is constant
True- False Thermophilic bacteria grow best at high temperatures because their cell membrane fluidity is optimal for transport of nutrients due to a predominance of saturated fatty acids.
True
The citrate test tests for:
a. ability to use citrate as a sole carbon and energy source
If you inoculate bacterium X into molten thioglycollate agar and the next day notice growth only at the bottom of the media, your organism is a(an):
c. obligate anaerobe
T/F Triclosan resistant bacteria may also be resistant to antibiotics such as tetracycline.
True
When following bacterial growth with a spectrophotometer, (complete the sentence)
c. as cell numbers increase, cell mass increases, light transmittance decreases due to increased light scattering and Absorbancy increases.
Before the discovery of antibiotics, AgNO3 drops were placed in the eyes of newborns who have passed through the birth canal to:
d. prevent blindness
Which one of the following is true of sterilization?
c. Autoclaving requires steam at high pressure ( 15lbs/in2.)
The function of the iodine in the Gram Stain is:
b. To act as a mordant and complex with crystal violet
Resolving power d= 0.5 um/2 NA. True/False. If the numerical aperture for the objective lense is 0.25, you WILL be able to see a bacterium that is 1 um in size. (Note: you need to calculate d)
True
Which one of the following characterizes the cell membrane? Read carefully.
a. Phospholipid bilayer, semi-permeable, hydrophilic and hydrophobic regions, contains proteins
Which of the following describes palisading?
c. Rod shaped cells aligned in a V shape or stacked next to each other
Given the resolving power at a given magnification is 0.4 um. True- False: You will be able to see two cocci (each 1 um wide)that are 0.2 um apart as two cocci.
False
Mannitol salts media has a high salt concentration. Staphylococcus is able to grow in the presence of the high salt but most other bacteria cannot grow. It also has mannitol ( as well as other nutrients that allow growth) and a pH indicator in the medium called phenol red. Staphylococcus species that can grow on mannitol produce acid that diffuses into the media changing the media to an acid range and the phenol red in the medium turns yellow. Staphylococcus species that cannot grow on mannitol but use the other nutrients do not produce acid and the phenol red in the medium stays pink. You would describe this media as
c. Selective and differential
Which one of the following statements IS true? Read carefully. Each sentence combines three concepts. (Note that resolving power d= wavelength/2 numerical aperture. Consider numerical aperture to be a constant)
c. As the wavelength decreases, resolving power decreases and magnification of an object by the objective lens forms a real image.
Which of the following do all organisms have?
d. Cytoplasmic (cell) Membrane
Which of the following can you tell from a simple stain? There is only one correct answer.
d. Cell shape
10 - 8 x 10-2=
a. 10- 10
MSDS stands for:
c. Material Safety Data Sheet
Which of the following is the strongest chemical bond in an aqueous solution?
- covalent bond
Which one of the following statements is true? Read carefully.
The condenser lens focuses light on the object( specimen) and the ocular lens magnifies the image of the specimen created by the objective lens.
Which of the following is used to place an organism into a specific Domain?
b. nucleotide sequence of ribosomal RNA( rRNA)
Which one of the following statements DOES NOT apply to Listeria monocytogenes?
A. Is primarily localized in the soil and rarely found in other habitats.
The microscope is said to be parfocal if:
- the object is still in focus switching from one objective lens to another.
You streak out a culture of Chromobacterium on a nutrient agar plate. When you look at the plate the next day you see that the colonies of Chromobacterium produce a purple pigment that diffuses through the media. Which of the following can you tell about the organism from this observation?
a. The organism produces a purple water soluble pigment.
In which one of the following types of microscopy does only scattered light enter the objective lens?
A. Darkfield
mutualism
both organisms benefit from the interrelationship
parasitism
one organism benefits (the parasite) while the other (the host) is weakened, sickened, or damaged
pathogen
microbe that usually produces the disease
opportunistic pathogen
causes disease most often if host defenses are compromised or impaired
compromised host
amount required to kill 50% of the population
as the LD50 increases
the toxicity decreases.
etiology
study of the cause of a disease
reservoir
source of disease- living and nonliving
carrier
asymptomatic human source of infection
zoonoses
diseases that are naturally spread from usual animal host to humans- often via vectors
Where on the body is lactic acid very predominant?
In mucous membranes in the oral cavity (throat and mouth) and in the vagina during child bearing years
Why do dental cavities occur more frequently in individuals who consume more sucrose as a sweetener compared to glucose?
Sucrose is converted to leven by lactic acid bacteria. Levan is a polysaccharide and is deposited outside of the bacterial cells as a slime layer and allows bacteria to stick to teeth and also serve as an instrument part of biofilm. Glucose and fructose will not produce levan or dextran.
Explain the appearance of gum drop colonies that form on TSA sucrose swabbed with bacteria from the human mouth and throat.
The gum droplets are due to the large amounts of polysaccharides excreted to the outside of the cell. Streptococcus salivarius and Streptococcus.
True/False? Recent research suggests a correlation between the type of intestinal flora and obesity.
True
Give two examples as to why breast feeding is advocated by the medical community.
Diarrheal disease is 3-4 times more likely in infants that are fed formula rather than breast milk. Human breast milk contains certain oligosaccharides that encourage the growth of Bifidobacterium, which prevents colonization by potential pathogens.
What are contributions of normal flora that play a role in human health?
- GI bacteria produce essential vitamins.
- Bacteria aid in digestion of food.
- Gut flora is altered with pregnancy.
- GI microflora play a role in a functional immune system and protect us from harmful bacteria (pathogens).
What is a biofilm?
Any group of microorganisms in which cells stick to eachother on a surface.
What is the infectious dose?
minimum # of cells needed to cause a disease
What are the steps to infection?
- Attachment to a specific receptor bacteria ---> fimbriae virus ---> proteins
- Invasion = get inside the host cytotoxins --> destroy the cell membrane/structure enzymes -->make cell membrane permeable
- Colonization/Reproduction= needed to reach infectious dose
- Disease
How do the bacteria attach to host cells?
Bacteria attach via the fimbriae, capsule, or slime layer.
Describe the steps in phagocytosis
- chemotaxis to microbe
- adherence of microbe to white blood cell
- formation of phagosome
- formation of phagosome with lysosome to form phagolysosome
- digestion of ingested microbe by enzymes
- expulsion of debris (wasted materials)
How does a phagosome differ from a phagolysosome
phagosome is an ingested particle phagolysosome is an ingested particle + a lysosome
How do pathogens survive intracellularly?
Lipid A- found in LPS of gram negative bacteria only
are endotoxins secreted outside of the cell membrane?
no
are endotoxins inactivated by heat?
no
can endotoxins be converted into toxoids?
no
what is the chemical composition of an exotoxin?
protein
are exotoxins secreted outside of the cell?
yes
are exotoxins inactivated by heat?
yes
can exotoxins be converted into toxoids?
yes
describe the AB type exotoxin
made of an A protein and a B protein stuck together.
- B always binds to cell and stimulates the cell to perform phagocytosis. A- damages host in some way
how does the AB exotoxin enter the human cell and cause damage? provide examples
- enters the human cell, and A and B dissociate from eachother.
- A disrupts some cell function EXAMPLES vibrio cholera toxin- massive H2O loss from intestinal cells, corynebacterium diptheriae- disrupts protein synthesis in respiratory cells E.coli 0157 (shigella) toxins causes diarrhea
What determines if an antigen is very immunogenic?
as size increases, antigenicity increases. as heterogenity increases, antigenicity increases. LARGER ANTIGEN= STRONGER IMMUNE RESPONSE.
define exogenous antigen
"nonself". antigen on the microbe antigen is foreign to the host but is found on the foreign invaders membrane.
define endogenous antigen
"nonself" host cell infected by a foreign invader and the host cell places the nonself antigens on the membrane to tell the immune system that its infected and ready to die
define auto-antigen
not foreign antigens; normally found on the outside of cells.
type of lymphocytes in humoral response
B lymphocytes
type of lymphocytes in cell mediated response
T lymphocytes
antibody production in humoral response?
yes
antibody production in cell mediated response?
no
do infected human cells get killed in humoral response?
no
do infected human cells get killed in cell mediated response?
yes
what type of antigen is recognized in humoral response?
exogenous antigen
what type of antigen is recognized in cell mediated response?
endogenous
what is an antibody?
True/False- Humans can recognize billions of exogenous and endogenous prior to an initial exposure.
True
Define BCR and TCR
BCR= B cell receptor TCR= T cell receptor
Where do B cells and T cells originate?
both originate in bone marrow.
Where do B cells and T cells mature?
B cells mature in the bone marrow. T cells mature in the thymus.
define colonial selection
B or T cell rapidly cloned when selected for by an antigen. then memory cells are produced, to prepare for faster response in the future.
define colonial deletion
- kills B cells that would attack our own antigens (forbidden clones)
True/False- Neutrophils have receptors in their cell membrane for the FC portion of an antibody.
True
what is the memory response?
where you have made memory T cytotoxic cells (inactive) and antibodies in response to antigens.
describe the first response of humoral immunity
- antigen interacts with t-helper cells
- T helper 2 cell binds with & activate b cells
- activated b cell differentiate into plasma & memory cell 4.B cells synthesize & secrete IgM
- plasma cells die quickly
- memory cells have identical BCR
- memory cells don't produce Ab during first exposure
describe the second response of humoral immunity
of Ab increases quickly due to exposure to exogenous Ag
- During 2nd exposure, antigen memory cells are activated
- memory cells differentiate into plasma cells and replicate quickly
- plasma cells reproduce antibodies
- 2nd exposure MUCH QUICKEr
describe the first response of the cell mediated immunity
1.Tc cell recognizes endogenous AgY via TCR 2.Clonal selection: AgY interacts with T-helper 1 cells
- Activated Tc cells proliferate and synthesize a TCR identical to that of the TCR that interacted with AgY
- The TCR will bind to endogenous AgY in infected cell membrane
- Perforin-granzyme pathway
- Tc cells are short lived
Describe the second response of cell mediated immunity
- 2nd exposure activates memory t-cytotoxic cells- have very high proliferation rate
- the TCR will bind to the endogenous AgY and kill cell
- 2nd exposure MUCH QUICKER
what role do T-helper cells play in the humoral and cell mediated immune response?
- Th1 stimulates cell mediated
- Th2 stimulates humoral response
how do cytotoxic t cells kill infected/cancer cells?
can bind to infected cell with a virus or bacterium (attaches then secrets perforin or granzyme which destroys/digests the cell
What does perforin do?
perforin will poke holes in the membrane
what does granzyme do?
granzyme will be added to tell cell to lyse
Why does HIV infect T-helper cells but not cytotoxic cells?
T helper cells have CD4. T cytotoxic cells have CD8. Host cell receptor for HIV is the CD4/C55 complex.
Explain how HIV infection leads to one becoming immune-compromised.
Explain how Rh- mom carrying an Rh+ fetus during her first pregnancy, protects her second Rh+ fetus from hemolytic anemia (erythroblastosis) during the second pregnancy.
during birth, blood transfer can occur from baby to mother, mothers immune system will make antibodies to the Rh+ antigen. second pregnancy may produce an Rh+ fetus, and rhogam will protect the baby
define immunization
increase resistance to disease by stimulation of immune system or passive transfer
vaccine
pathogen or antigen which induces protective immunity
serotype
distinct variation of bacteria or virus (type A or B)
toxoid
non toxic but immunologically similar toxin
conjugate vaccine
immunization created by joining an antigen to a protein molecule
anti-toxin
antibody that counteracts a toxin
auto-antibody
autobody manufactured by the immune system that is directed against one or more of the individuals own proteins
auto-immune disease
arise from an abnormal immune response of the body against substances and tissues normally present in the body
anti-venin
antitoxin against the venom of snakes, spiders, or venomous object
antiseptic
antimicrobial substance applied to living tissue/skin to reduce possibility of infection
antibiotic
medication that kills bacteria or inhibits bacterial growth
antibody
immunoglobulin
antigen
substance that causes your immune system to create antibodies against it
list an advantage and a disadvantage to a live attenuated pathogen
advantages: avirulent (can't cause disease), can replicate in host, fewer boosters, long lasting disadvantages: side effects, contamination, can revert back to virulent, can't give to pregnant people
list advantage and disadvantage to a inactivated vaccine
advantage: cannot revert disadvantage: weak, can't replicate, needs boosters, exogenous antigen, not as strong as live attenuated, can cross placenta
list advantage and disadvantage to a purified vaccine
advantage: removes side effects from whole pathogen disadvantage: can't replicate, needs boosters, secondary response
list advantages and disadvantages to a toxoid vaccine
advantage: fairly strong pathogen because its a protein disadvantage: modified purified Ag, needs boosters, still weak, only humoral response
genetically engineered vaccine
takes the gene coding for the infectious protein and puts it into a plasmid
Which is the most antigenic type of vaccine?
Live attenuated pathogen- produces strong humoral response, constantly replicating. if infects host cells, strong cell mediated response long lasting protection
5 characteristics of the "ideal vaccine"
- low side effects
- protection against wild type
- stimulates humoral and cell mediated immunity
if the vaccine is not extremely immunogenic, or doesn't build up a strong memory response, then several exposure may be needed.
define the DTaP vaccine
has diptheria toxoid, tetanus toxoid, and acellular pertussis (whooping cough), purified antigen
describe DBT vaccine
DPT has diptheria, tetanus, and acellular pertussis toxoid, but once caused a fever up to 105-106 degrees which led to mental disability for life.
how does hemolytic anemia differ from hemolytic uremia?
hemolytic anemia=red blood cells are lysed hemolytic uremia= E. coli 0157 causes bleeding of the kidneys.
name two autoimmune disorders in humans
(when the body makes antibodies to itself)
- Rheumatoid Arthritis
- Lupus
- Diabetes Type 1
True/False. Someone received all three shots of the gardisal vaccine. Following the primary response to the vaccine, she can be assured that she is protected from cervical cancer associated with HPV.
False
Why is infant botulism an infection while adult botulism is an intoxication?
In adult botulism, the bacterial cell is not present but the toxin is, resulting in an intoxication. Infants do not have the normal gut flora built up so they receive the entire microbe, resulting in an infection.
humoral, cell mediated, or both? production of Ab
humoral
activation of T-cytotoxic cells?
cell mediated
T-helper cells required?
both cell mediated and humoral
memory response?
both cell mediated and humoral
exogenous Ag?
humoral
endogenous Ag?
cell mediated
perforin/granyzme role?
cell mediated
CD4 receptor?
both cell mediated and humoral
specificity towards pathogen?
humoral
is there an effective vaccine for staphylococcus aureus?
no
Neisseria gonorrhea vaccine?
no
corynebacterium diptheriae vaccine?
yes
hemophilus influenzae vaccine?
yes- HIB conjugate vaccine
streptococcus pneumoniae vaccine?
yes
Neisseria meningitidis vaccine?
yes
bortadella pertussis vaccine?
