1.1 Bacteria: structure and classification Flashcards
Eukaryote
an organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus
Prokaryote
a microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles
Eukaryote
Prokaryote
Eukaryotes and prokaryotes both have?
Cell membran + cytoplasm + DNA
Have a nucleus and membrane bound organelles?
eukaryotes
no-membrane bound organelles, no nucleus
prokaryote
large, complex cells
eukaryotes
small, simple cells
prokaryotes
Gram Staining process:
- Crystal violet
- iodine
- alcohol (decolorization)
- safranin (counterstain)
morphology and color are based on
cell wall structure
gram negative
gram positive
Pairs (diplococci)
Chains (streptococci)
Clusters (staphylococci)
rods =
bacilli
The first steps to identification…
Flagella:
- present in some bacteria
- involved in motility and chemotaxis
Fimbriae / Pili:
- Predominantly found in Gram-negative bacteria
- Shorter, straighter, and thinner than flagella
Fimbriae: attachment to surfaces, including other cells
Pili: join bacterial cells for conjugation (DNA transfer)
Capsule:
- polysaccharides
- confers mucoid appearance to colonies
- protection from phagocytosis, antimicrobials
- enhances adherances
play a part in enveloping the cell?
cell wall
outer membrane
plasma membrane
cell wall:
maintain bacterial shape
- prevent cell from osmotic lysis
- extends as needed while volume of cell increases
Is a target for antimicrobials?
cell wall ( not present in eukaryotes)
the cell wall is made up of?
peptidoglycan
Unusual case, doesn’tve a cell wall?
Mycoplasma spp antimicrobials targeting this cell wont work
bacterial envelope: gram-positive
- many layers of peptidoglycan
- technic acid: provides rigidity and used for antigentic typing
bacterial envelope: gram-negative
- thin peptidoglycan
- outer membrane
Gram +: alcohol
dehydrates PG = more permeable
Gram -: alcohol
dissolves crystal violet and makes holes in thin PG = crystal violet washed out
crystal violet enters via
cell walls
what does iodine do?
binds crystal violet = to big to leave cell wall
Phospholipid bilayer:
- Hydrophilic head
- Hydrophobic tails
- Only small lipid-soluble compounds can enter the cell by passive diffusion
- Transporters/porins for transport of other molecules
outer membrane =
LPS
outer membrane function:
- Protect from phagocytosis
- Barrier to antimicrobials e.g. penicillins * & enzymes, detergents, bile salts etc
Plasma (cytoplasmic) membrane
- Encloses the cytoplasm
- Phospholipid bilayer and proteins
- Permeability barrier with transport systems for selective transport of substances in and out of the cell (selective permeability)
- Bacterial respiration (ATP synthesised using electron transporters on membrane)
- Anchor for external structures
- Target for disinfectants and antimicrobials
cytoplasm:
- Facilitate chemical reactions and to dissolve solutes
- Contains cell components (e.g. nucleoid and ribosomes)
- aqueous solution to macromolecules, small molecules, and inorganic ions
site of protein synthesis?
ribosomes
