Exam 3 Segment Playposit Questions: Bacterial Pathogens

Why are bacterial toxins well-known among virulence factors?

They can be easily purified from bacterial supernatant

What is the role of horizontal gene transfer (HGT) in the evolution and spread of toxin-producing bacteria

it allows rapid spread of toxin genes among bacteria

Which bacterial toxin is primarily associated with Shigella bacteria but can also be produced by certain strains of E. coli?

Shiga toxin

What is the primary component of LPS endotoxin found in Gram-negative bacteria

Lipid A

Which class of toxins possesses both cytotoxic and immunosuppressive properties

mycolactone toxins

Which bacterium is responsible for causing Buruli ulcer

Mycobacterium ulcerans

Type I toxins primarily act on the

Host cell surface

Type III Toxins have an A-B structure with 2 functional components, where the B component:

Binds to the host cell surface

Superantigens exert their effects by binding to

T-cell receptors (TCRs)

Which type of hemolysis causes the lysis of surrounding RBCs, leaving a yellowish zone

beta-hemolysis

Pore-forming toxins cause cell lysis by:

Forming channels in the membrane

Clostridium perfrinogens produces an alpha-toxin that causes:

gangrene

A-B toxins, also known as type III toxins, typically have 2 functional domains or subunits. The A domain is responsible for

Conferring toxic activity, usually enzymatic

The B domain of A-B toxins:

Facilitates the translocation of the A domain across the membrane

Proteolytic cleavage separates the A and B domains in A-B toxins, which remain connected by a:

disulfide bond

The host cell specificity of A-B toxins is determined by:

The B domain

AB-type toxins consist of

A and B portions

Which organism produced neurotoxins

Clostridium botulinum

AB-type toxins have two main portions: A and B. The A portion is responsible for:

Enzymatic activity, often ADP-ribosylation

The T domain of AB-type toxins is

involved in toxin transfer inside the host cell.

What is the hallmark symptom of diphtheria

Grayish pseudo membrane formation

how does the diphtheria toxin enter the host cell's cytoplasm

endocytosis and translocation through the endosome membrane

what is the function of the A subunit of the diphtheria toxin

Catalyzing ADP-ribosylation of EF-2

how is diphtheria toxin expression regulated in Corynebacterium diphtheria

by the chromosomal gene dtxR

What is the purpose of using Botox injections

- to reduce the depth of wrinkles

- to treat urinary incontinence

- to prevent severe scarring during wound healing

how if botulinum toxin protected from stomach acids and protease enzymes in the GI tract

the nontoxic components of the progenitor toxin provide protection

what is the specific effect of the botulinum neurotoxin on peripheral neurons

inhibition of neurotransmitter release

what role do SNARE proteins play in normal neurotransmission

they help mediate vesicle docking and fusion

what is the role of an antitoxin in the treatment of botulism

neutralizing the botulinum neurotoxin

Which term refers to the trafficking of proteins from the cytosol through the cell membrane

Translocation

What are the Sec and Tat pathways?

Protein secretion systems in both Gram-negative and Gram-positive bacteria

Which protein secretion systems are Sec-dependent in gram negative bacteria

type 2 and 5

What is the role of the Sec system

Translocating proteins from the cytosol to the periplasm

What is the unique characteristic of the tat system

it transports fully folded proteins

What is the role of the N terminal signal sequence in the Sec system

Guides the protein to its destination

Which bacteria fold the transported protein in the periplasmic space

gram negative bacteria

Which system is the most common mechanism in bacteria for protein translocation

post translational system

What happens to the signal sequence after protein secretion or export

it is cleaved by peptidases

Which protein complex acts as an unfolded polypeptide-conducting channel in the Sec system

SecYEG translocon

What is the role of SecA in the post translational mechanism of the Sec system

Binds to the signal peptide of the secretion substrate protein

Quorum sensing in bacteria relies on the production and detection of small diffusible signaling molecules called

Autoinducers

Autoinducer concentrations increase as cell density

increases

What are autoinducers in quorum sensing

small, diffusible signaling molecules used by bacteria to coordinate their activities

Which statement is true regarding autoinducers

Autoinducers contribute to inter-species interactions and communication between different species of bacteria

Which molecules are primarily used as autoinducers in gram negative bacteria

N-acyl homoserine lactones (AHLs)

Which molecules are primarily used as autoinducers in gram positive bacteria

Autoinducing peptides (AIPs)

How do autoinducing peptides (AIPs) facilitate intraspecies communication in gram positive bacteria

They remain in the extracellular environment and interact with membrane receptor proteins

What is the advantage of autoinducer-2 (Al-2) in interspecies cell-cell communication

Al-2 indicates the presence of other bacteria regardless of their type

What is the role of Vibrio-fischeri in the Bobtail squid?

It serves as a symbiont within the squid's light organ

What happens under conditions of high cell densities in Vibrio fischeri

Phosphatase activity is activated, reducing biofilm formation

What is the role of cholera toxin in Vibrio cholerae infection

It disrupts ion flow control, leading to water loss and watery diarrhea

What are the two autoinducer molecules involved in quorum sensing in Vibria cholerae

CAl-1 and Al-2

Which of the following is NOT a characteristic of Staphylcoccus aureus

- Ability to infect various organs

- Commensal nature

- Inability to form biofilms

- Ability to acquire antibiotic resistance

Which system regulates the growth-phase-dependent expression of virulence factors in Staphylococcus aureus?

Agr quorum sensing system

What is the function of the AgrD gene in Staphylococcus aureus?

encoding a precursor peptide for AIP synthesis

How do AIPs from different staphylococcal species interfere with each other's signaling?

They compete for the same receptor binding site

How many distinct secretion systems do gram (-) bacteria have

six

Which secretion system shuttles proteins from the cytoplasm to the extra cellular space

type I

Which type of secretion system injects products into the cytoplasm of other cells

type III

Which type of secretion system is commonly used to secrete AB toxins

Type II

Which system requires the Sec translocon complex to translocate proteins across the cytoplasmic membrane

Type II secretion system

Which systems are evolutionarily related to the type II secretion system

Type IV pili biogenesis system and competence system for DNA uptake

The type 1 secretion system transports proteins:

from the cytoplasm to the cell surface

the type 1 secretion system consists of three components which of the following is NOT one of these components

A: inner membrane protein

B: Adaptor protein

c: ATP-binding cassette (ABC) transporter or proton anti porter

D: outer membrane pore

(A)

The type 3 secretion system (T3SS) is used by bacteria to

inject toxic effector proteins into host cell cytosol

The T3SS injectisome seals off before the needle structure is assembled to

ensure that effector proteins are only secreted upon contact with the host cell

Chaperone proteins in the T3SS guide the effector proteins and are responsible for

Unfolding the effectors for secretion

In Yersinia, the signal for translocation in the T3SS is

contact between the host membrane and the bacteria

The conjugation system of the type four secretion system is responsible for:

transferring DNA and proteins to another recipient bacterium

The type six secretion system (T6SS) is evolutionarily related to

Bacteriophage T4 tail and baseplate

The T6SS has a unique capability to deliver effector molecules

into the adjacent cell when in close proximity to the T6SS spike

In gram-positive bacteria, protein secretion can occur through both Sec-dependent and Sec-independent mechanisms. Which of the following is an example of a Sec-dependent mechanism?

sortase system

The SecA2 accessory system in gram positive bacteria is responsible for exporting

Serine-rich glycosylated virulence factor proteins

The cytolysin-mediated translocation (CMT) system in Streptococcus pyogenes is functionally similar to which secretion systems found in gram-negative bacteria

Type III and type IV secretion systems

What distinguishes Yersinia pestis from Yersinia pseudotuberculosis

- deletions and acquisitions leading to enhanced transmission potential

- acquisition of a gene enabling efficient colonization of the midgut

- formation of biofilms in the foregut of fleas

All of the above

How is Yersinia enterocolitica primarily transmitted

Consumption of contaminated pork

Which cells in the Peyer's patches are targeted by Yersinia for binding and penetration

M cells

What is the preferred route of dissemination for Yersinia after colonization

lymphatic system

Which of the following is an adhesion used by Yersinia to facilitate attachment to host cells

Invasin

How does Yersinia regulate its mobility and attachment to host cells based on temperature?

Decreased motility and increased attachment at higher temperatures

What modification does Yersinia make to its lipopolysaccharide (LPS) structure at higher temperatures?

it becomes tetra-acylated

What is the function of cytosolic chaperones in Yersinia infection

to ensure proper folding and secretion of Yop effectors

How do YopP/YopJ and YopH contribute to the evasion of the host immune response?

By inhibiting NF-kB and MAP-kinase signaling pathways

What type of cell death is induced by Yersinia infection?

apoptosis, necrosis, pyroptosis

What is the main difference between bacteriostatic and bactericidal compounds in antimicrobial therapy?

Bactericidal compounds kill bacteria, while bacteriostatic compounds inhibit bacterial growth.

Bacteriostatic substances are most suitable for patients with

Intact immune systems

What does the MIC test determine?

the lowest concentration of an antibiotic required to prevent bacterial growth

What does the large size of the clearance zone in the Kirby-Bauer Assay indicate?

The high effectiveness of the antibiotic in inhibiting bacterial growth.

What is the primary difference between disinfectants and antiseptics?

Disinfectants are used on surfaces, while antiseptics are used on the skin

Which phase of antibiotic discovery is considered the most challenging and time-consuming?

Lead optimization

Why have pharmaceutical companies lost interest in antibiotic discovery?

challenges and costs involved in the process.

Why do antibiotics primarily focus on a limited set of targets?

These targets have been successful in the past

What is the final step in peptidoglycan biosynthesis?

Cross-linking of peptidoglycan

What is the target of the antibiotic fosfomycin?

Conversion of UDP-NAG to UDP-NAM

Which step of peptidoglycan biosynthesis is targeted by bacitracin?

Phosphorylation and recycling of undecaprenyl pyrophosphate.

Which antibiotics act on the transpeptidation step of peptidoglycan biosynthesis?

beta-lactams

What is the role of penicillin-binding proteins (PBPs) in peptidoglycan biosynthesis?

catalyzation of transpeptidation reactions

How do β-lactam antibiotics inhibit transpeptidase enzymes?

by opening the beta-lactam ring and forming a covalent bond

What is the additional activity possessed by fourth-generation cephalosporins compared to third-generation cephalosporins?

resistance to beta-lactamase enzymes

Which enzyme do glycopeptides like vancomycin and teicoplanin bind to?

transpeptidase enzymes