Inteoduction To Bacteria Flashcards
Describe the structure of bacteria
They have single chromosomes and no nucleus. They have cell walls and also capsules which are a virulence factor. Flagellum help the bacteria move in the host and fimbriae help the bacteria attach to cells.
How do Gram positive and gram negative bacteria differ?
They both have a plasma membrane, periplasmic space and peptidoglycan but Gran negative bacteria also have an outer membrane of lipopolysaccharide and protein.
What is the gram staining process?
The sample is put on a slide and left to dry so the bacteria stick. It is then heated up. The purple primary stain is added then iodine is added and the crystal violet and iodine form a complex. Acetone alcohol is added so gram negative bacteria lose the purple stain due to the lipid layer dissolving in the solvents. The red secondary stain is added which stains the gram negative bacteria.
Name the four types of flagellum structures in bacteria
Monotrichous have one flagella coming out one side.
Lophotrichous have multiple flagellum coming out one side.
Amphitrichous have one flagella coming out each side.
Peritrichous have multiple flagellum all over.
What is conjugation?
A bacteria (F+) forms a bridge of pilus to another bacteria (F-) which allows F- to gain a plasmid so both bacteria are now F+. Endonuclease cleaves the origin of transfer on the plasmid. Replication helps form a new plasmid.
How do bacteria replicate and how do they get variation?
By binary fission and they have spontaneous mutation and transfer of DNA.
Transfer of DNA can be through transformation which is when bacteria take up free DNA from dead bacteria or transduction which is where a phage goes inside a bacteria.
What is a bacteriophage?
It is a virus that eats bacteria but not humans so is good for therapy.
Name two types of mediums?
Enriched mediums such as agar.
Selective mediums that inhibit the growth of bacteria and support the growth of one specific strain.
