60 Questions
What is the definition of pathogenicity?
The ability of a parasite to inflict damage on the host
How do pathogens typically adhere to epithelial cells?
Through interactions between molecules on the pathogen and host tissues
What are adhesins on a pathogen's surface primarily composed of?
Glycoprotein or lipoprotein
What is the critical factor in establishing an infection for pathogens?
Portal of entry
What are host receptors that pathogens bind to primarily composed of?
Extracellular matrix, cell surface glycoproteins, membrane lipids
Which of the following is a function of the complement system?
Boosting the efficiency of both innate and adaptive immune responses
What is the role of toll-like receptors in phagocytes?
Recognizing and interacting with specific pathogen-associated molecular patterns
What is a key transcription factor activated in many different pathways in phagocytes?
NFκB (nuclear factor kappa-light-chain-enhancer)
What is the main role of leukocytes at the site of infection during inflammation?
Releasing proinflammatory cytokines to increase vascular permeability
What can lead to septic shock in the body?
Systemic inflammation and increased vascular permeability
What is the main function of Granzyme?
Induces apoptosis (programmed cell death)
What is the role of Interferons in the immune response?
Serve as a warning system and prevent viral replication
What is the function of T lymphocytes (T cells) in the immune response?
Defend against intracellular pathogens
What is the characteristic of B lymphocytes in terms of specificity?
Display membrane-bound immunoglobulins on their surface with specificity to one antigen
What is the main characteristic of adaptive immunity?
Directed toward specific molecular components of the microbes
What is the function of bacterial capsules in pathogenicity?
They serve for adherence and protection
What is the role of adherence structures such as fimbriae, pili, and flagella in bacterial infections?
Implicated in specific bacterial infections
What is the process of colonization in the context of host-pathogen interactions?
The growth of microorganisms in host tissues, usually beginning in mucous membranes
What is the significance of virulence attenuation in pathogen strains?
It is important for vaccine development
When do opportunistic infections occur?
In compromised hosts, such as individuals with weakened immune systems or noninfectious diseases
Which cells primarily drive innate immunity?
Phagocytes
What is the process of differentiation of blood stem cells into different blood cells influenced by cytokines and chemokines called?
Hematopoiesis
Which type of stem cells produce T cells, B cells, and natural killer cells?
Lymphoid stem cells
What is the main function of lymph nodes?
Contain high concentrations of immune system cells
What is the primary driving force behind competitive exclusion by harmless microbes?
Limiting available nutrients and sites for infection
Which of the following is true about coagulase and streptokinase?
Coagulase and streptokinase are virulence factors that manipulate blood clotting, affecting the immune system's ability to combat infections.
What is the mechanism of action of Diphtheria exotoxin?
Blocks protein synthesis by ADP-ribosylation of the elongation factor EF-2.
What is the function of Botulinum toxin?
Inhibits muscle contraction by cleaving proteins involved in releasing acetylcholine.
What is the role of endotoxins in bacterial pathogenesis?
Endotoxins are released when bacterial cells lyse and are generally less toxic than exotoxins.
What is the difference between innate immunity and adaptive immunity?
Innate immunity is the nonspecific immunity of multicellular organisms that targets pathogens seeking to colonize the host, while adaptive immunity is the acquired ability to recognize and destroy specific pathogens or their products.
What is the function of a virion in the context of viruses?
To facilitate transmission of the virus
What is the primary role of capsid in a virus?
To surround the genome of the virus
What is the characteristic of enveloped viruses?
They have an outer layer made of phospholipid bilayer and viral proteins
What is the outcome of a lysogenic infection?
Host cell genetically altered because viral genome becomes part of host genome
How can viruses be classified based on their genetic material?
DNA or RNA genomes, single or double-stranded
What is the main function of virion surface proteins in a virus?
Host cell attachment and may include enzymes involved in infection/replication
What is the primary driving force behind the maintenance of small microbial genomes?
Gene deletions
What evolutionary mechanism plays a significant role in microbial evolution by allowing DNA transfer between distant evolutionary branches?
Conjugation
Which genetic event is more frequent in microbial genome dynamics, contributing to the maintenance of small microbial genomes?
Gene deletions
What is the result of a gain-of-function mutation in E. coli after 31,500 generations?
Ability to utilize citrate
What role do gene families, including homologs, orthologs, and paralogs, play in genome evolution and diversification?
Crucial role
What allows one gene copy to evolve new functions while the other maintains the original function?
Gene duplication
What is the primary driving force behind competitive exclusion by harmless microbes?
Competition for nutrients and space
What is the characteristic of B lymphocytes in terms of specificity?
They undergo clonal selection and expansion
What is the role of endotoxins in bacterial pathogenesis?
Inducing fever and inflammation
What is the main function of Granzyme?
Inducing apoptosis in infected cells
What is the main role of leukocytes at the site of infection during inflammation?
Engulfing and destroying pathogens
What are host receptors that pathogens bind to primarily composed of?
Protein and carbohydrate complexes
What is a characteristic of the influenza A virus genome?
It is segmented
What is the causative agent of COVID-19?
SARS-CoV-2
What is a characteristic of lysogeny maintenance in phages?
It is maintained by phage-encoded repressor protein
What is a feature of retrovirus integration into the host genome?
It involves dsDNA integration into the genome by integrase
What is the primary source of genetic diversity in viruses?
Mutation
What is the role of viroplasms in some eukaryotic cells during viral infection?
Formation of viroplasms
What can be inferred from >97% SSU rRNA sequence identity?
The same species
What is the primary purpose of stable isotope probing in microbial communities?
Identify microorganisms utilizing specific compounds
What does metaproteomics measure in a microbial community?
Protein diversity and abundance
What is the advantage of using multilocus sequence analysis over SSU ribosomal RNA genes for distinguishing species?
Can distinguish species that cannot be resolved by rRNA sequences
What is the main role of stable isotopes and isotopic fractionation in microbial ecosystems?
Trace the biological or geological origin of ancient environments
What is the significance of microbial diversity in ecosystems?
Expressed through species richness and abundance
Study Notes
Exotoxins and Innate Immunity in Bacterial Pathogenesis
- About 2 million people in the United States are affected by various medical procedures such as surgery, biopsy, catheterization, and hypodermic injection, with a mortality rate of approximately 5%.
- Pathogenic bacteria release enzymes that break down the host's tissues, such as hyaluronidase from Streptococcus pyogenes and collagenase from Clostridia causing gangrene.
- Coagulase and streptokinase are virulence factors that manipulate blood clotting, affecting the immune system's ability to combat infections.
- Exotoxins, including AB toxins, cytolytic toxins, and enterotoxins, cause disease by inhibiting host cell function or killing host cells.
- Diphtheria exotoxin, produced by Corynebacterium diphtheriae, blocks protein synthesis by ADP-ribosylation of the elongation factor EF-2.
- Botulinum toxin, produced by Clostridium botulinum, inhibits muscle contraction by cleaving proteins involved in releasing acetylcholine.
- Tetanus toxin, produced by Clostridium tetanus, floods neuromuscular junctions with acetylcholine, causing muscle contraction.
- Cholera enterotoxin, produced by Vibrio cholera, causes massive fluid secretion into the intestinal lumen by affecting cellular processes and ionic balance.
- Cytolytic exotoxins degrade the cytoplasmic membrane, causing cell lysis and death, often through phospholipase activity or pore formation.
- Endotoxins, part of the lipopolysaccharide component of Gram-negative bacterial outer membranes, are released when bacterial cells lyse and are generally less toxic than exotoxins.
- Innate immunity is the nonspecific immunity of multicellular organisms that targets pathogens seeking to colonize the host and involves rapid responses by phagocytes.
- Adaptive immunity is the acquired ability to recognize and destroy specific pathogens or their products, involving a response by lymphocytes and post-exposure immunity.
Microbial Ecosystems and Diversity: Key Concepts and Analytical Approaches
- Nucleotide sequence differences between homologous genes reflect accumulated mutations since a common ancestor, and can be used to infer relationships
- SSU ribosomal RNA genes are highly conserved and easily sequenced for inferring relationships; >97% SSU rRNA sequence identity indicates the same species
- Multilocus sequence analysis using protein-encoding genes can distinguish species that cannot be resolved by rRNA sequences
- Whole genome analysis is increasingly common, allowing reconstruction of metabolic/physiological characteristics and estimation of relatedness using average nucleotide identity
- Metaproteomics measures protein diversity and abundance in a microbial community, while metabolomics analyzes cellular and extracellular metabolites
- Direct chemical measurements and microsensors are used to measure specific metabolites and activities in microbial habitats
- Stable isotopes and isotopic fractionation can trace the biological or geological origin of ancient environments
- Stable isotope probing involves feeding microorganisms with labeled substrates to identify those utilizing specific compounds in a microbial community
- Microbes account for ~50% of all biomasses on Earth, residing in various habitats within ecosystems
- Microbial diversity is expressed through species richness (total number of species) and abundance (proportion of each species) in an ecosystem
- Guilds, consisting of metabolically related microbial populations, form communities that interact with macroorganisms and abiotic factors
- Microbes play essential roles in biogeochemical cycles, including the transformations of key elements such as C, N, S, and Fe, through oxidation-reduction reactions
Test your knowledge of exotoxins and innate immunity in bacterial pathogenesis with this quiz. Explore the effects of pathogenic bacteria's enzymes and virulence factors, as well as the mechanisms of action of various exotoxins such as diphtheria, botulinum, tetanus, and cholera toxins. Gain insights into the interplay between innate and adaptive immunity in combating bacterial infections.
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