test two lec 8 Flashcards
for detailed studies of microbes they need to be grown separately in a….
pure culture
how many organisms have we cultured
.1%
what are the two main types of culture media
liquid or broth medium
solid medium
anaerobes use slant tubes
what are the two ways to isolate pure cultures
dilution streaking
spread plate technique
what is dilution streaking
dragging loop across the surface of an agar plate
what is spread plate technique
serial dilutions are performed on a liquid culture
a small amount of each dilution is then plated
early dilution of spread plate technique show
confluent growth
what is important about spread plate technique
viable bacteria produced and used to replicate
what does viable bacteria mean
one that successfully replicates to form a colony
what do we call organisms that metabolize but don’t replicate
viable but non culturable
maybe didnt find proper plate conditions
what is a complex media
bacterial growth solution that is nutrient rich but poorly defined
difficult to characterize metabolism of an organism
what is enriched medium
complex medium plus additional components
such as blood
helps mimic host environment
what kind of nutrients are found in complex media
yeast extract beef extract amino acids peptides nucleosides vitamins some sugars
what is synthetic media
bacterial growth solution that contains defined known components
why use synthetic media
used to study metabolic needs of different types of organisms
what are some components in synthetic media
H2O
various salts
C, N
energy sources
what is selective media
favor the growth of one organism over another
example of selective media
medium containing bile salts and crystal violet favors growth of gram neg over pos
what is differential media
exploit differences between two species that grow equally well, but differ in some biochemical aspect
example of differential media
e coli and salmonella
both gram neg
e coli ferment lactose which lower ph and changes dye of med to red
what is a macconkey medium
both selective and differential
selects gram neg due to bile salts and crystal violet
includes lactose, ferment and turn red
non fermenting is white
what is a petroff hausser counting chamber
microorganisms can be counted directly by placing dilutions on a special microscope slide
hemocytometer