spectrophotometry
measurement of transparency at a particular wavelength or a series of wavelengths
absorption spectra
can identify compounds
absorption amount
at right wavelength can quantify compounds
pairs
di-
clusters
staph-/staphylo-
chains
strepto
groupings are related to…
plane of cell division
plsmid
tiny ring of DNA
capsule slime layer
may or may not be present
gram negative
cells as pink
gram positive
cells are Purple
bacterial cell wall structure
threads of repeating carbs (NAG-NAM) glued together with proteins
peptidoglycan
sugars and protein compound
what determines if a cell wall is gram pos or gram neg?
amount of peptidoglycan
What makes cell wall durable?
cross-linking
penicillin works by…
blocking cross-linking by transpeptidases
describe gram positive cells
- multiple layers of peptidoglycan
- teichoic acids keep layers together and increase (-) charge of cell wall
describe gram negative cells
- single layer of peptidoglycan (1/10th of gram pos)
- a second phospholipid membrane outside the peptidoglycan
second phospholipid membrane of gram neg help….
repel some immune factors, block entry of antibiotics and can contain toxic compounds
types of bacterial staining
- gram stain
- acid fast stain
- negative stain
- flagella stain
- endospore stain
bacterial smears
- usually first step in staining
- mix colony with drop of water on slide
- allow to dry
- heat fix
gram stain process
- crystal violet
- rinse
- iodine
- rinse
- alcohol
- rinse
- safranin
during alcohol wash….
gram neg cells are stripped of the purple (outer membrane)
acid fast stain
- waxy cell walls repel gram stain
- primary dye carbol-fuschin has high affinity for waxy mycelia acids
- acid-alcohol removes dye from most cells
- counterstain with methylene blue
