Alison Brown Flashcards
- How can prokaryotes be distinguished from eukaryotes?
Prokaryotes and eukaryotes can be distinguished through a variety of ways, for example, eukaryotes have a nucleus present and their organelles are membrane bound while prokaryotes do not possess either of these. However, prokaryotes contain peptidoglycan in their cell walls while no eukaryotes do.
- What are the main constituents of Gram positive and Gram-negative cell walls?
Gram-positive cells are purple in colour when stained, while gram-negative cell walls stain red. This is due to the uptake of crystal violet in the cell walls of gram-positive cells as the layer of peptidoglycan is significantly larger than that of gram-negatives. While peptidoglycan and techoic acids make up gram-positive cell walls, lipopolysaccharides make up most of the gram-negative cell walls as well as a small percentage of peptidoglycan.
- How does an aerobe differ from an anaerobe or facultative aerobe?
An aerobe is bacterium that can only grow in the presence of oxygen; conversely, anaerobes can only grow in environments without oxygen present. Facultative aerobes are flexible, with the ability to grow in either environment.
- What are Archaea bacteria?
Archaea bacteria are bacterium that lack peptidoglycan, are extremophiles and are also classified as methanobacterium due to their ability to produce natural gas.
- How do bacteria move?
Bacteria have this nifty gadget of a organelle called flagellum, which is a long, thin structure that enables mobility.
- Which of the following bacteria would have teichoic acid? Salmonella, clostridium, bacillus, E. coli.
Clostridium is the only one that has teichoic acids since it is the only gram-positive bacteria out of the list. Gram negatives do not have teichoic acids.
- What is an endospore and how does this help bacteria survive?
Endospores are what bacteria emit in order to be able to “respawn”, therefore prolonging its life and their ability to survive.
- Indicate the Genus, species and strain names below. What does O157 indicate? Escherichia coli O157.
Escherichia is the genus, coli is the species and O157 indicates the strain.
- Name three structures that are external to the cell and describe whether they contribute to the cell’s pathogenicity.
Adhesions, they allow for the bacteria to adhere to the cell and hence override the host defences. Toxins also interfere with the normal functioning of a cell’s defences. Thirdly, enzymes also help as a virulence factor.
- What are ‘Transient Flora’ and what is the difference between a primary pathogen and a opportunistic pathogen?
Transient Flora are found on the skin surfaces. Primary pathogens infect healthy hosts, and opportunistic pathogens are pathogens that people are exposed to more frequently, however only show symptoms when the host is immunocompromised/unhealthy.
- What are adhesions? Give two examples.
Adhesins are used for the attachment of the bacteria onto a cell; it also has the ability to override the host cell’s defences.
- What are virulence factors?
Virulence factors are molecules excreted by pathogens to achieve colonization, evasion of the immune response, entry in and out of the cells, inhibiting the host’s immune response and obtaining nutrition from the host.
- How do most microbes enter the body?
Through transmission from another host.
Enterotoxin
A toxin that affects the GIT lining of the body
Neurotoxin
interferes with nerve impulses
Toxoid
a chemically modified toxin from a pathogenic microorganism
- List the differences between exo and endotoxins.
Exotoxins:
• Produced by both gram-negative and gram-positive bacteria
• Many types based on structure and function
• Heat labile
• Specific effects on host
Endotoxins • Produced by only gram-negative bacteria • Only one type of endotoxin • Heat stable • Diverse range of effects on host
- What is the primary role of the normal body flora?
Normal body flora have protective effects, such as preventing pathogens (defence), produces vitamins etc.
