Microbiology Lecture 3 Flashcards
Do all bacteria have cell walls?
Most do, some like mycoplasma do not.
True or false
Fimbriae are used in locomotion.
False, main use is in attachment/adhering.
True or false
Flagella are used in locomotion,
True.
Define glycocalyx.
A capsule or slime layer external to the cell wall.
What is a glycocalyx made from?
Polysaccharides, sometimes polypeptides or both.
What allows the difference in glycocalyx structure?
If arranged tightly, it is a capsule, if loose, it is a slime layer.
What is the purpose of the glycocalyx?
Allows attachment to surfaces forming a biofilm.
Encapsulated bacteria are also more difficult to kill.
How can encapsulated bacteria be stained?
Negative staining on the bacteria, and then a background stain to reveal the capsule.
What does attachment of bacteria to surfaces activate?
Biofilm-specific genes, including cell-cell signalling molecules.
What is the function of pili?
Involved in genetic transfer between bacteria via conjugation.
What is the function of fimbriae?
Enables bacteria to attach to surfaces and form biofilms.
What are fimbriae like compared to flagella?
Fimbriae are shorter, straighter, and thinner than flagella.
What are pili like compared to fimbriae?
Longer than fimbriae, only a few present on the surface.
How do flagella induce motion?
By rotating.
What are flagella powered by?
A motor - a rod surrounded by a series of rings.
Do flagella induce an immune reaction?
Yes.
What are the subunits and structure of flagella?
Are helices, made of flagellin subunits.
From where does the flagella extend?
Extends from the cytoplasmic membrane, through the cell wall.
How do bacteria know where to move?
Chemotaxis using chemoattractants/repellents.
Name and define the 4 types of flagella.
Monotrichous - single
Lophotrichous - tuft at one end
Polar - one at each end
Peritrichous - many located around the cell
Define the three types of motion seen in a hanging drop test.
Brownian motion - not true motility, caused by bacteria colliding with water.
Streaming motility - not true motility, caused by currents in the water.
True motility - bacteria will move in different directions, not all in the same direction.
Aside from a hanging drop test, how else can bacteria be tested for motility?
Use semisolid media.
Motile bacteria will show diffuse growth through the tube.
Non-motile bacteria will only grow at the inoculation point.
Define sporulation.
Endospore production.
What prompts sporulation?
Desiccation.
Where are endospores mostly found?
In soil bacteria.
Do endospores stain?
Not with the typical ones.
Are endospores toxic?
They can be during sporulation or germination. Proteins required for these processes may be toxic - indirect.
How are endospores dehydrated?
Contain dipicolinic acid, which complexes with calcium ions to dehydrate it.
What do cyanobacteria have to help them float and why?
Gas vacuoles for light exposure - photosynthesis.
What are the surface lipids of mycobacteria made of, and why dont gram stains work on them? What is a way of staining them?
Mycolic acid, cant be gram stained as it is water-based. Need a lipid-based stain like acid-fast stain.
