MCB 100 MIDTERM 2 QUESTIONS & ANSWERS
Diphtheria toxin is _______ that _______ resulting in __________
a. a pore=forming toxin | inserts into membranes | cell lysis
b. an AB-type neurotoxin | inhibits neurotransmission | flaccid paralysis
c. a superantigen | stimulates immune cells | massive inflammation
d. an AB-type toxin | ADP-ribosylates EF2 | stopping protein synthesis
e. a membrane lipid A-like endotoxin | stimulates inflammation | toxic shock - Answers -
d. an AB-type toxin | ADP-ribosylates EF2 | stopping protein synthesis
A-B toxins are very modular and in nature can swap parts of their genes to make
chimeric toxins with new hybrid properties. Suppose you have identified a new hybrid
AB toxin. The A Part resembles diphtheria toxin (DT), while the B Part resembles
botulinum toxin (BoNT). What would injection of a hybrid toxin, DT-BoNT, into an animal
do to its nerve cells?
a. Cause cell lysis
b. Cause paralysis
c. Cause tissue swelling
d. Kill the cells
E. Nothing - Answers -d. Kill the cells
Diphtheria Toxin (DT) - Answers -
Botulinum Toxin (BoNT) - Answers -
"Universal Tree of Life" - Answers -Based on sequence comparisons of ribosomal small
subunit 16S rRNA genes
- Present in prokaryotes
- Do not encode proteins, encode ribosomal RNA (essential for protein making, have to
be highly conserved)
- Any mutation will greatly change the ribosome and will make it traceable
What are the three different domains of life? - Answers -Bacteria, Archaea, and
Eukarya
What is the basis for assigning organisms into the three different domains of life
(Bacteria, Archaea, and Eukarya)?
a. DNA structure and location
b. Presence of flagella
c. Method of reproduction
d. rRNA gene sequences
e. Type of staining used to see them - Answers -d. rRNA gene sequences
Central Dogma - Answers -DNA ---> RNA ---> Protein
, - DNA to DNA: Replication
- DNA to RNA: Transcription
- RNA to Protein: Translation
Typical Prokaryote Structure - Answers -- Flagellum: senses environment and is used
to direct the bacteria
- Capsule; protective layer against environment
- Cell Wall
- Outer membrane: peptidoglycan
- Inner membrane: around cytoplasm
- Cytoplasm: everything inside the plasma membrane (Ribosome, plasmid, nucleoid,
inclusion)
- Nucleoid: DNA
- Not in a compartment, spread inside the cytoplasm
- Transcription + translation occur in cytoplasm
- Plasmid: might contain non-chromosomal DNA
Sporulation - Answers -Bacteria: survival mechanism; convert into a spore as a period
of hibernation until conditions change (e.g more nutrients)
- Not done by all bacteria, but most can (esp. environmental)
Fungus: reproductive spores; part of sexual cycle
Microbial Biofilm - Answers -Advantages:
- Decreased diffusion of oxygen creates a new micro-niche
- Enhanced resource trafficking between cells
- Increased resistance to antibiotics
- Increased communication between cells
Disadvantages:
- Increased predation by amoeba and other Eukaryotic microbes
- Cells clustered in one place = easier for predators
When does a biofilm usually begin to form? - Answers -Formation begins when free-
floating cells attached to a surface and each other
- Attach using a polysaccharide coating (sugar, sticky)
- The biofilm composition is diffuse and can be washed away
Which of the following statements about biofilm is TRUE?
a. In biofilms there is often metabolic cooperation between bacteria
b. In biofilms all the bacteria are living, but those that die are released into the medium
c. In a single-species biofilm, the interior environment is uniform throughout
d. The environment of the biofilm matrix is not conductive to uptake if colored dyes
e. Bacteria in biofilms cannot continue to grow at low nutrient concentrations - Answers
-a. In biofilms there is often metabolic cooperation between bacteria
Diphtheria toxin is _______ that _______ resulting in __________
a. a pore=forming toxin | inserts into membranes | cell lysis
b. an AB-type neurotoxin | inhibits neurotransmission | flaccid paralysis
c. a superantigen | stimulates immune cells | massive inflammation
d. an AB-type toxin | ADP-ribosylates EF2 | stopping protein synthesis
e. a membrane lipid A-like endotoxin | stimulates inflammation | toxic shock - Answers -
d. an AB-type toxin | ADP-ribosylates EF2 | stopping protein synthesis
A-B toxins are very modular and in nature can swap parts of their genes to make
chimeric toxins with new hybrid properties. Suppose you have identified a new hybrid
AB toxin. The A Part resembles diphtheria toxin (DT), while the B Part resembles
botulinum toxin (BoNT). What would injection of a hybrid toxin, DT-BoNT, into an animal
do to its nerve cells?
a. Cause cell lysis
b. Cause paralysis
c. Cause tissue swelling
d. Kill the cells
E. Nothing - Answers -d. Kill the cells
Diphtheria Toxin (DT) - Answers -
Botulinum Toxin (BoNT) - Answers -
"Universal Tree of Life" - Answers -Based on sequence comparisons of ribosomal small
subunit 16S rRNA genes
- Present in prokaryotes
- Do not encode proteins, encode ribosomal RNA (essential for protein making, have to
be highly conserved)
- Any mutation will greatly change the ribosome and will make it traceable
What are the three different domains of life? - Answers -Bacteria, Archaea, and
Eukarya
What is the basis for assigning organisms into the three different domains of life
(Bacteria, Archaea, and Eukarya)?
a. DNA structure and location
b. Presence of flagella
c. Method of reproduction
d. rRNA gene sequences
e. Type of staining used to see them - Answers -d. rRNA gene sequences
Central Dogma - Answers -DNA ---> RNA ---> Protein
, - DNA to DNA: Replication
- DNA to RNA: Transcription
- RNA to Protein: Translation
Typical Prokaryote Structure - Answers -- Flagellum: senses environment and is used
to direct the bacteria
- Capsule; protective layer against environment
- Cell Wall
- Outer membrane: peptidoglycan
- Inner membrane: around cytoplasm
- Cytoplasm: everything inside the plasma membrane (Ribosome, plasmid, nucleoid,
inclusion)
- Nucleoid: DNA
- Not in a compartment, spread inside the cytoplasm
- Transcription + translation occur in cytoplasm
- Plasmid: might contain non-chromosomal DNA
Sporulation - Answers -Bacteria: survival mechanism; convert into a spore as a period
of hibernation until conditions change (e.g more nutrients)
- Not done by all bacteria, but most can (esp. environmental)
Fungus: reproductive spores; part of sexual cycle
Microbial Biofilm - Answers -Advantages:
- Decreased diffusion of oxygen creates a new micro-niche
- Enhanced resource trafficking between cells
- Increased resistance to antibiotics
- Increased communication between cells
Disadvantages:
- Increased predation by amoeba and other Eukaryotic microbes
- Cells clustered in one place = easier for predators
When does a biofilm usually begin to form? - Answers -Formation begins when free-
floating cells attached to a surface and each other
- Attach using a polysaccharide coating (sugar, sticky)
- The biofilm composition is diffuse and can be washed away
Which of the following statements about biofilm is TRUE?
a. In biofilms there is often metabolic cooperation between bacteria
b. In biofilms all the bacteria are living, but those that die are released into the medium
c. In a single-species biofilm, the interior environment is uniform throughout
d. The environment of the biofilm matrix is not conductive to uptake if colored dyes
e. Bacteria in biofilms cannot continue to grow at low nutrient concentrations - Answers
-a. In biofilms there is often metabolic cooperation between bacteria
