Bacterial Appendages and Development Flashcards
(14 cards)
What types of protein appendages do bacteria produce?
Fimbriae (numerous and short) and pili (long and less numerous)
What do fimbriae and pili do?
Tips of pili and fimbriae can interact with (for example) proteins and lipids on the surface of epithelial cells in the gut to help the bacterial cell attach to the host cell
What are capsules? What do they do? How do they stain?
Dense, well-defined polysaccharide or protein layer closely surrounding a cell. They are protective and bind water, which may enable the cell to resist desiccation. They can promote adherence to eukaryotic host cell surfaces and promote colonization. Encapsulated bacteria can resist phagocytosis by immune system cells, possibly because they are large and slimy. They can also aid bacterial cell to cell contact, which promotes biofilm formation. When staining, capsules remain clear.
What do Pseudomonas aeruginosa do?
They can cause infections in humans, especially a colonization of the lungs of cystic fibrosis patients
What is a flagellum? What are differences between aqueous environments and solid surfaces?
Flagellum are bacterial appendages that mediate motility. In aqueous environments, we see movements of singe cells called ‘swimming’. On solid surfaces, bacteria pile into one another to from a swarm, called ‘swarming’.
What does the flagellum consist of?
The flagellum consists of a wide section called a hook (connects the filament to the flagellar motor in the base); the flagellar motor is anchored in the cytoplasmic membrane and cell wall. The motor consists of a central rod that passes through a series of bushes or rings. The rotor and motor are within the basal body, and the basal body uses proton motive force as the energy source to rotate the flagellum. The flagellum can rotate at more than 100 000 RPMs, and cells can move up to 60 cell lengths per second.
How are flagella shaped?
Flagella are helical
Why is the flagellum critical for the human immune system?
The flagellum protein has a wavelength that is characteristic of the flagellum for any given species. When bacterial cells invade the human body, the protein flagellum is recognized by the innate immune system via a cell receptor that promotes an inflammatory or immune response. Pathogens may sometimes alter features of the flagellum (modify the protein or simply do not express the flagellum during infections) to evade immune system cells.
What are the four different types of flagellum?
Monotrichous: only one flagellum
Amphitrichous: two flagella, one from either end of the cell
Lophotrichous: multiple flagella arising from the same point in the cell
Peritrichous: multiple flagella distributed across the entire cell surface
Describe the flagellum of an E. Coli. How does it move? Is it useful for anything other than motion?
When an E. Coli cell swims above the surface of a eukaryotic cell that it might infect, the flagella beat. As the E. Coli cell comes in to land on the host cell, the flagella make contact with receptors in the host cell surface; then, the membrane of the E. Coli cell makes contact with the host membrane, and an infection can be established
How do bacteria achieve directional movement? What does changing the rotation of the flagella do?
Bacteria achieve directional movement by changing the direction of rotation of the flagella. When the flagella rotate in a counterclockwise direction, it results in a run (meaning that the bacteria moves in a particular direction). When the flagella rotate in a clockwise direction, the cell ceases forward motion and is at the mercy of surrounding liquid, resulting in tumbles.
What is chemotactic behaviour?
Bacteria move away or towards substances in their immediate environment. Bacteria can often sense their surroundings and behave accordingly; they move towards food, resources, and signals provided by other bacteria through quorum sensing, and away from toxic micro environments
What are endospores? What produces them and why? How are they spread?
Endospores are produced by some Gram-positive bacteria and are differentiated cells that are highly resistant to heat, cold, chemicals, and radiation; it is a mechanism for survival in deleterious environments (ex. low nutrients). A vegetative cell develops into one viable protected cell (the endospore). Endospores present health concerns as they are incredibly difficult to kill and can survive for millions of years. They are dispersed by wind, water, and animals, and can exist in soil over winter or through many years. After it senses improved conditions, the spores will germinate and resume growth.
How are endospores formed?
- DNA replicates and is segregated to opposite ends of the cell.
- Membranes form around the DNA
- Forespore forms additional membranes around the forespore
- Protective cortex, made by protein synthesized in both the mother cell and spore, forms around the spore
- Protein coat forms around the cortex
- Spore is released and mother cell dies; spore remains viable
