Microbiology Quiz on Pathogens and Viruses

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Questions and Answers

What does H.pylori produce to neutralize stomach acid in its vicinity?

Lactic acid

Pepsin

Urease (correct)

Ammonium chloride

How does Bordetella pertussis compromise the host’s respiratory function?

By blocking airways directly

By destroying red blood cells

By increasing mucus production

By killing ciliated epithelial cells (correct)

What type of secretion system does Enteropathogenic E.coli (EPEC) use?

Type III secretion system (correct)

Type II secretion system

Type IV secretion system

Type I secretion system

What effect does pertussis toxin have on the host's G protein?

It causes the G protein to remain in an inactive GDP-bound state Signup and view all the answers

What is a key characteristic of H.pylori in relation to disease?

It can persist for life without causing disease in most individuals Signup and view all the answers

What role do flagella play for H.pylori in the stomach?

Chemotactic motility to penetrate mucus Signup and view all the answers

What is the primary outcome of the adhesion of Bordetella pertussis to ciliated epithelial cells?

Impaired respiratory clearance Signup and view all the answers

What is the function of the receptor protein Tri in Enteropathogenic E.coli (EPEC)?

To bind to host intestinal epithelial cells Signup and view all the answers

Which of the following is NOT one of the six general categories that viruses rely on to be successful?

Mutation of viral proteins Signup and view all the answers

How does a virus acquire an envelope?

Through budding from the host-cell plasma membrane Signup and view all the answers

What is the role of the capsid in a virus?

To protect the viral genome and facilitate entry into host cells Signup and view all the answers

What is one method by which pathogens, such as Yersinia pestis, enter their host?

Via blood meal from an infected host Signup and view all the answers

Which of the following best describes the function of viral genome replication?

To facilitate the formation of progeny virus particles Signup and view all the answers

Why is it significant that vaccination and immunization lead to decreased disease incidence?

It enhances the host's immune response against pathogens Signup and view all the answers

How does H. pylori persist in the stomachs of its host?

By forming thick biofilms that protect it from stomach acid Signup and view all the answers

What is indicated by the statement 'a single virion can produce thousands of progeny'?

Viral replication is highly efficient within host cells. Signup and view all the answers

What unique structure is formed on the cell surface due to the action of certain pathogenic bacteria?

Pedestal Signup and view all the answers

Which receptor is primarily used by HIV in its early stages of infection?

CD4 Signup and view all the answers

Who might have immunity to HIV infection?

Individuals with an altered CCR5 gene Signup and view all the answers

Which of the following correctly describes the 'fusion with plasma membrane' entry strategy of HIV?

It directly fuses with the host cell's plasma membrane. Signup and view all the answers

What is the primary action of the zipper mechanism used by bacteria?

It binds to a host-cell receptor with high affinity. Signup and view all the answers

Which strategy employs endosomal membrane disruption to release viral content into the cytosol?

Endosomal membrane disruption Signup and view all the answers

Which cells are most efficiently infected by HIV variants that utilize CXCR4?

Helper T cells Signup and view all the answers

What role do Rho family small GTPases and Arp2/3 complex play in the action of bacterial mechanisms?

They promote actin polymerization at the site of bacterial attachment. Signup and view all the answers

What is the role of actin filaments in the movement of bacterial pathogens within host cells?

They actively push pathogens through the cytosol at rates of up to 1 um/min. Signup and view all the answers

What is the primary mechanism by which L.monocytogenes escapes the phagosomal membrane?

It secretes listeriolysin O to disrupt the phagosomal membrane. Signup and view all the answers

How do pathogens facilitate their entry into neighboring cells without exposure to the extracellular environment?

By forming long, thin protrusions that engulf bacteria. Signup and view all the answers

How does M.tuberculosis evade the phagosome?

It prevents the maturation of the early endosome. Signup and view all the answers

What is the function of effector proteins secreted by bacteria in relation to host cell actin?

They mimic or interact with host cell actin nucleators to promote actin assembly. Signup and view all the answers

In how do viruses utilize the axonal transport system for their movement within host neurons?

By attaching to dynein and kinesin motor proteins for transport. Signup and view all the answers

What strategy does S.enterica employ to slow phagosomal maturation?

It injects effector proteins that alter host trafficking. Signup and view all the answers

What do the effector proteins injected by L.pneumophila do?

They prevent phagosomes from fusing with endosomes. Signup and view all the answers

What is the consequence of bacterial pathogens colliding with the host cell membrane?

It leads to the formation of actin tails that propel them forward. Signup and view all the answers

What unique movement strategy do some viruses use once they infect sensory neurons?

They utilize retrograde axonal transport towards the microtubule minus end. Signup and view all the answers

At what pH level does listeriolysin O become less active in L.monocytogenes?

Below 6 Signup and view all the answers

Which system does L.pneumophila use to inject its effector proteins into the phagocyte?

Type IV secretion system Signup and view all the answers

What happens to the actin filaments as the bacterial pathogens advance through the cytosol?

New filaments are formed at the rear, leaving a trail. Signup and view all the answers

What is a significant outcome of S.enterica's alteration of phagosome maturation?

Formation of Salmonella-containing vacuole. Signup and view all the answers

How do some pathogens manipulate autophagy mechanisms in host cells?

By interfering with the formation of autophagosomes. Signup and view all the answers

Which cellular structures do viruses acquire their envelope from during budding?

Plasma membrane, ER, Golgi, or nuclear membrane Signup and view all the answers

What is one method that viruses use to manipulate the autophagy process in host cells?

They deploy a protective shield to prevent detection. Signup and view all the answers

What is a consequence of viruses encoding proteins that modify the host's transcription/translation apparatus?

Viral RNAs and proteins are favored over host cell proteins. Signup and view all the answers

What are the two main advantages that allow pathogens to evolve rapidly?

Quick replication and extensive mutational variation. Signup and view all the answers

How does antigenic variation benefit trypanosomes?

It allows them to evade antibody-mediated clearance. Signup and view all the answers

What is a common reason that RNA and DNA replication is error-prone among viruses?

Viruses often lack certain proofreading enzymes. Signup and view all the answers

Which of the following describes the function of endonucleases encoded by some viruses?

They cleave the 5' cap from host-cell mRNAs. Signup and view all the answers

In what way do selective pressures influence the evolution of pathogens?

They act rapidly on existing genetic variation. Signup and view all the answers

What is the primary role of a trypanosome's variable surface glycoprotein (VSG)?

To provide a surface for immune evasion. Signup and view all the answers

Study Notes

Pathogens and Microbiota

Pathogen: An organism, cell, virus, or prion that causes disease, exploiting host cell attributes for infection.
Microbiota: Collective of microorganisms residing on or in an organism.

Primary and Opportunistic Pathogens

Primary Pathogen: Causes overt disease in most healthy individuals, often spreading rapidly between hosts. Some can persistently infect a single host for years without overt symptoms.
Opportunistic Pathogen: Normal flora microbes causing disease only when host immune systems are weakened or they gain access to normally sterile areas. Four characteristics of successful pathogens: Entering the host (breaking barrier), Finding a suitable niche, Avoiding the host's immune system, and Replicating to spread.

Gram-Positive and Gram-Negative Bacteria

Gram-Positive Bacteria: Stain positive with Gram stain due to a thick peptidoglycan cell wall layer outside their plasma membrane.
Gram-Negative Bacteria: Do not stain with Gram stain, due to a thin peptidoglycan cell wall outside their inner membrane, covered by an outer membrane.
Lipopolysaccharide (LPS): Component of Gram-negative bacterial outer membranes.
Pathogen-Associated Molecular Patterns (PAMPs): Shared molecular structures/molecules by many pathogenic bacteria and some viruses. PAMPs are recognized by the host immune system.

Horizontal Gene Transfer

Horizontal gene transfer: Genes are transferred between bacteria and archaea via three mechanisms: natural transformation (release of naked DNA), transduction (infection by bacteriophages), or conjugation (sexual exchange).
Genomics variation: Within a bacterial species, a certain degree of genomic variation is seen, with some bacterial species having core genomes common to all isolates and larger pangenomes containing additional genes present in subsets of isolates.

Bacterial Shapes and Structures

Bacterial shapes: Various shapes like cocci (spherical), bacilli (rod-shaped), spirilla (spiral).
Cell surface features: Gram-positive or gram-negative, and various appendages that may contribute to virulence.

Bacterial Pathogenicity

Virulence genes: Encode proteins that contribute to an organism's ability to cause disease.
Virulence factors: Proteins encoded by virulence genes that contribute to disease.

Pathogen Entry Strategies and Virulence

Pathogen entry to host: Common entry points are wounds or by being transferred (e.g. to a non-immune host) via a vector.
Yersinia pestis: Multiplies in the flea's foregut; block the digestive tract; transmitted to a new host.
Helicobacter pylori: Persists in the stomach by neutralizing stomach acid using urease; was identified as a microbial cause of stomach ulcers.
Bordetella pertussis: Colonizes respiratory epithelium; produces toxins that disable and kill ciliated cells (impeding host's clearing mechanism).
Enteropathogenic E. coli (EPEC): Uses a type III secretion system to inject proteins, enabling the bacteria to attach to intestinal cells, triggering actin polymerization, and forming cellular protrusion (pedestal).

Viral Strategies and Mechanisms

Viral Structures: Viruses can be either DNA or RNA viruses and have various morphologies.
Viral Entry: Viruses use various strategies to enter cells which can include: (1) fusion with the host membrane, (2) endocytosis, (3) pore formation, (4) endosomal membrane disruption.
HIV infection: HIV infection uses CD4, CCR5 co-receptor (early stages) and CXCR4 co-receptor to enter host cells.

Intracellular Pathogens

Intracellular pathogens: Some pathogens use various strategies to survive within host cells and avoid the host's immune response mechanisms.
L. monocytogenes: Avoids being killed by lysosomes, it secretes listeriolysin O, which disrupts the endosome/phagosome membrane; allowing replication in the cytoplasm.

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Description

Test your knowledge on various pathogens such as H.pylori, Bordetella pertussis, and Yersinia pestis. This quiz covers their mechanisms of action, effects on the host, and characteristics that contribute to disease. Challenge yourself with questions about virus structure and functioning as well.