Cell Structures - Virulence Factors And Toxins Flashcards
What kinds of flagella can bacteria have?
- Single polar flagellum : Vibrio cholera.
- Many peritrichous flagella all around the cell : E.coli and Proteus mirabilis.
- Periplasmic flagella : spirochetes.
What is the structure by which the flagellum is affixed to the bacteria?
By a basal body, which spans through the entire cell wall, binding to the inner and outer cell membrane in gram negative bacteria and to the inner membrane in gram-positive bugs (the gram-positive bacteria don’t have an outer membrane).
Does shigella have flagella?
No!
What are the Pili (also called fimbriae)?
- Straight filaments arising from the bacterial cell wall, making the bacterium look like a porcupine.
- They are much shorter than flagella and do not move.
- Serve as adherence factors - adhesins.
Mention some bacteria that have pili and utilize them as adhesins.
- Neisseria gonorrhea : pili that allow it to bind to cervical cells and buccal cells to cause gonorrhea.
- E. coli + Campylobacter jejuni cannot cause diarrhea without their adhesins to bind to the intestinal epithelium.
- Bordetella pertussis uses its adhesin to bind to ciliated respiratory cells and cause whooping cough.
What are the components of the bacterial capsule?
They are usually composed of simple sugar residues.
Bacteria secrete these sugar moieties, which then coat their outer wall.
What is unique about Bacillus anthracis’ capsule?
It is made up of amino acid residues.
What is the main significance of a bacterial capsule?
Capsules enable bacteria to be more virulent because macrophages and neutrophils are unable to phagocytize the encapsulated buggers. (e.g. Streptococcus pneumoniae)
What are the two important tests that enable doctors to visualize capsules under the microscope and aid in identifying bacteria?
- India ink stain : the capsule appears as a transparent halo around the cell. (used primarily to identify the fungus Cryptococcus)
- Quelling reaction : bacteria are mixed with antibodies that bind to the capsule.
What contains a vaccine against streptococcus pneumoniae?
Antigens from the 23 most common types of capsules.
What are the two genera of bacteria that form endospores?
- The aerobic Bacillus
- The anaerobic Clostridium
Both gram positive.
What are the components of the endospores multilayer?
- A cell membrane
- A thick peptidoglycan mesh
- Another cell membrane
- A wall of keratin-like protein
- An outer layer called the exosporium
What is a biofilm?
An extracellular polysaccharide network, similar to the capsule polysaccharides, that forms a mechanical scaffold around bacteria. It allows them to bind to prosthetic devices, like IV catheters, and protects them from attack by antibiotics and the immune system.
What is the main action of facultative intracellular organisms?
These bacteria inhibit phagosome-lysosome fusion.
Mention 8 important facultative intracellular organisms.
- Listeria monocytogenes
- Salmonella typhi
- Yersinia
- Francisella tularensis
- Brucella
- Legionella
- Mycobacterium
- Nocardia