PHD - Nature of Bacteria (May) Flashcards by Nicolas Dawson

Explain why transduction is necessary for the virulence of Corynebacterium diphtheriae?

It’s toxin is in a bacteriophage that has to infect the organism for it to become virulent

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True or False: Flagellin is non-immunogenic.

False

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Which protion of lipopolysaccharide is endotoxic?

Lipid A

The lipopolysaccharide is unique to gram negative bacteria. It is made up of a core polysaccharide, an O-antigen, and a lipid A (endotoxin).

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Once the F factor is integrated into the genome of the host cell, it is called, what?

High frequency recombination (HFR)

The F factor is a set of genes within the chromosome of the bacterial cell that has the capacity to integrate into the chromosome

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What is the component of spores that makes them highly resistant to heat?

Dipicolinic acid

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What is the factor that determines whether or not a cell can form a sex pillus?

What TYPE of secretion is this?

F factor (F+)

Type IV secretion

The F-factor allows the bacterium to produce a sex pillus so that it can pass its genes to another bacteria.

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True or false: almost all of the resistance genes are on transposons.

True

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In Gram positive bacteria, what are the two structures analogous to lipopolysaccharide in gram negative bacteria?

Lipoteichoic acid

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Differentiate between peritrichous, monotrichous, and polar flagella.

Peritrichous - multiple flagella on a single bacterium
Monotrichous - only one flagellum
Polar - small bundle of flagella located at one or both ends of the cell

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Which antibiotic prevents the attachment of the 50s ribosomal subunit?

Clindamycin and chloramphenicol

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Replicative transposons, in addition to a transposase gene, must have what gene?

Resolve Gene

Resolve gene encodes for resolvase, an enzyme that brings both ends of the transposon together so it can be cleaved.

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What are aerotolerant bacteria?

Bacteria that can tikerate oxygen, but only for short periods of time.

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Basic transposition relies on what enzyme for movement throughout the genome?

Transposase

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What is the purpose of the bacterial capsule?

Slimy coating made up of sugar molecules that:

Prevents engulfment of bacteria by phagocytes
Prevents immune cells from recognizing bacterial cell surface antigen

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What do transposases bind to on the DNA sequence?

Inverted repeats on each side of the transposon

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What does Bacitracin block? How?

Bactoprenol

Bacitracin inhibits dephosphorylation of bactoprenol, a molecule responsible for moving peptidoglycan subunits out of the cytoplasm and into the periplasmic space of gram positive bacteria.

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How many moles of ATP are produced in bacteria during the Embden-Meyerhof pathway? What about the Entner-Doudoroff pathway?

Embden-Meyerhoff (glycolysis) makes 2 ATP

Entner-Doudoroff makes 1 ATP

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What antibiotic is used in block proteoglycan to prevent the elongation of D-alanines?

Cycloserine

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What is the alternative to the Embden-Meyerhof pathway in bacteria? What are the end products?

Entner-Doudoroff Pathway

End products: glyceraldehyde-3-phosphate, 1 ATP, pyruvate

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In what part of the cell is ATP generated for bacteria?

Cytoplasm

Proton gradient between cytosol and periplasmic space stimulates ATPase

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Bacterial RNA polymerase is targeted by what antibiotic?

Rifampin

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What are microaerophilic bacteria?

Bacteria that need oxygen to grow, but only need about 5% O₂

Grow with increasing CO₂ levels

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Explain the mechanism of action of penicillin.

Prevents cross-peptidation during peptidoglycan synthesis

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True or False: sporulation is the bacterium’s method to avoid the death phase.

True

Spores are heat resistant, UV resistant, and anti-bacterial resistant

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Which class, gram positive or negative, have two cell membranes?

Gram Negative

What are lysozymes and which class of bacteria are they ineffective against?

Lysozymes are enzymes that cleave beta-1,4-glycosidic linkages, which are common in bacterial cell walls. These are ineffective against archaea

During the lysogenic pathway of viral transduction, what prevents the prophage from expressing its virulence within the cell?

Protein repressor expressed by the virulent genome shuts off all virulence functions of the bacteriophage Viral DNA is integrated in the host genome and is repressed until viral DNA has been replicated and phage assembly has taken place

What is a prophage?

A DNA sequence from a bacteriophage that has integrated itself into the bacterial genome.

What is the protein that makes up the flagellum?

Flagellin

What are the two ways in which viral transduction of bacteria can occur?

1. Lytic Pathway 1. Viral DNA hijacks cell machinery to assemble viral progeny that then burst out of the cell to infect other cells 2. Lysogenic Pathway 1. Viral DNA is integrated into bacterial genome and replicated silently Lysogenic pathway can become the lytic pathway when the repressor protein is degraded

What induces sporulation?

A sign or threat to life: heat, cold, low nutrients, dessication

What process do anaerobic bacteria use to bypass their lack of O₂ and Fe³⁺ to act as a molecular acceptor?

Fermentation Organic compounds act as both electron donors and acceptors. Uses pyruvate to form ethanol.

Rifampin targets what enzyme in the bacterial cell?

RNA polymerase

Explain how a non-virulent bacterium mixed with heat-killed virulent bacteria can lead to infection induction within a host.

Bacterial Transformation Dead virulent bacterial DNA enters the genome of the non-virulent strain and transforms it into deadly pathogens

What is the critical component of sporulation that allows a bacterium to become quiescent?

Dessication

What type of transposon has the capacity to change position within a chromosome or plasmid?

Replicative Transposon

True or False: Archaea lack peptidoglycan walls.

True. Remember that lysozymes, enzymes that break down bacterial cell walls, do not work on archaea. This is because they don't have cell walls.

Differentiate between flagella and common pili.

* Flagella - used for locomotion, made up of flagellin * Pili - used for adhering to surfaces and other bacteria, made up of pililin

Explain why Staphylococcus aureus is unique in its structural integrity.

It forms a pentaglycine cross-linkage in which integrity is maintained

What enzyme is found in aerotolerant bacteria, which protects them from O2-derived free radicals?

Superoxide Dismutase

Bacteria need iron for survival. The body has 10^-18 M and bacteria need 10^-5 or 10^-6 M. How do they overcome this low [Fe] in the host?

Siderophores Molecules with high affinity for Fe. They steal iron from host cells.

Which class of bacteria do not have superoxide dismutase or catalase for protection against O2-derived free radicals?

Obligate anaerobes

What is the most critical element in establishing genetic variation in bacteria, which can lead to antibiotic resistance?

Basic homologous recombination

In the stages of bacterial growth, what is the term used to describe optical density?

Turbidity

What is the function of cycloserine?

Inhibits the formation of peptidoglycan by blocking D-alanine elongation

What is the function of the antibiotics, clindamycin and chloramphenicol?

Prevents the attachment of the 50S subunit onto mRNA

Differentiate between generalized transduction and specialized transduction.

* Generalized - transfer of any bacterial DNA * Specialized - limited to specific DNA sites

How can gram negative cells have similar protection as gram positive cells?

Gram negative bacteria have an outer cell membrane, which allows exchange of products and gives protection. Gram negative cells also have lipopolysaccharide for protection.

True or False: Hfr conjugation can lead to antibiotic resistance and formation of virulence factors.

True. Hfr can contain pathogenicity islands, virulence, factors, and genes to increase survival as well as antibiotic resistance genes.

What are the four types of mutations in bacterial genetic makeup?

1. Replacement - transition or transversions 2. Deletion 3. Insertion 4. Inversion

What gene must be in an insertion sequence for it to be effective?

Transposase

To what is teichoic acid anchored to? What about lipoteichoic acid? These are found in gram positive or gram negative bacteria?

Teichoic acids are anchored to peptidoglycan. Lipoteichoic acids are anchored to the cell membrane. Found in Gram positive bacteria

What is the primary component which determines whether or not a bacterium is going to be gram positive or gram negative?

The size of the peptidoglycan layer Gram positive - thick peptidoglycan Gram negative - thin peptidoglycan

What are the mandatory receptors and replication sites of Hfr which allow conjugation to occur?

* Pilus receptor - binding site for pilus to initiate conjugation or facilitate adhesion to host cell * OmpA (outer membrane protein A) - facilitate bacterial adhesion and invasion * Plasmid Replication site * Restriction

What are the two types of genetic replacements?

1. Transition - purine to purine, etc. 2. Transversion - pyrimidine to purine, etc.

What metalic element is essential in all bacteria?

Iron

What is the mechanism of action of tetracycline? Streptomycin?

Bind the 30S ribosomal subunit and prevent translation of bacterial RNA

What class of bacteria have superoxide dismutase and catalase?

Aerobic Any bacteria that uses oxygen needs these two enzymes to be able to deal with free radicals formed.

What is the basis of the structural integrity of peptidoglycan walls?

Cross-linking of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) sugars between a D-alanine and an L-lysine

In transformation of bacteria, what must be done to DNA in order for it to be recognized as, "self?"

Methylation of specific bases If DNA from other source is not homologous, it will be digested by endonucleases before it can be integrated in the host genome. Having certain bases tagged makes the cell think that this foreign DNA is part of the cell, giving it time to integrate.

What form of iron is used as an energy source in bacteria? Which form is used as a terminal electron acceptor?

Energy source: Fe²⁺ Terminal electron acceptor: Fe³⁺

The antibiotic vanomycin blocks what? How?

Vancomycin interupts peptidoglycan synthesis through the blocking of bactoprenol transportation of peptidoglycan

What are the three stages of bacterial culture growth?

1. Exponential Growth 2. Stationary State 3. Death

What are two examples of bacteria that can undergo sporulation?

Bacillus and Clostridium

What are the elements of an insertion sequence?

1. 2 direct repeats 2. 2 inverted repeats 3. Transposition genes

In bacterial aerobic respiration, the TCA cycle yields high amounts of what organic product? These products are used for what?

NADH and FADH₂ Used for establishing a proton gradient to fuel the electron transport chain

What antibiotics block 30s from binding to mRNA?

Streptomycin and tetracycline

Pathogenicity islands in bacteria are transferred to other genes through what process?

Conjugation from Hfr bacteria to normal bacteria

True or false: a flagellum is ATP-driven.

False. Flagellum is driven by proton motive force.

True or false: antibiotic resistance is very common in an insertion sequence or a transposon.

True

Which drug prevents peptidoglycan crosslinking, or cross-peptidation?

Penicillin

What element can be used to prevent the expression of Diphtheria toxin? Why?

Iron Iron interacts with the repressor protein to inhibit expression of the toxin gene

True or false: conjugation occurs in Gram negative bacteria only.

False

What is the most common method of horizontal gene transfer?

Conjugation

What are the three classes of horizontal gene transfer?

1. Conjugation 2. Transduction 3. Transformation