MICROBIAL GROWTH PT.2 Flashcards
Classification of Culture Media
Culture media according to consistency
Culture media according to composition
Culture media according to their function
and use.
Culture media according to consistency:
Liquid media
Solidified media
are used for growth of pure
batch cultures
Liquid media
contain agar and are
used widely for the isolation of pure
cultures, for estimating viable bacterial
populations, and a variety of other
purposes
Solidified media
Culture media according to composition.
Chemically-defined (synthetic) medium
Complex (undefined) medium
is one in which the exact chemical
composition is known.
Chemically-defined (synthetic) medium
is one in
which the exact chemical constitution of
the medium is not known
Complex (undefined) medium
Complex (undefined) medium Also known as
basal medium
Culture media according to their function
and use.
Enrichment media
Supportive media
Selective media
Differential media
contain specific
nutrients required for the growth of
bacterial pathogens that may be present
alone or with other bacterial species in a
patient specimen
Enrichment media
Enrichment media EXAMPLE
Blood, Chocolate agar
contain nutrients that
support growth of most non-fastidious
organisms without giving any organism a
growth advantage.
Supportive media
contain one or more
agents that are inhibitory to all organisms
except those being sought.
Selective media
Selective media EXAMPLE
MacConkey agar, (GRAM -)
Eosin methylene blue (GRAM -)
employ some factors
that allows colonies of one bacterial
species or type to exhibit certain metabolic
or culture characteristics that can be used
to distinguish them from other bacteria
growing on the same agar plate.
Differential media
Bacterial Mutation
Spontaneous mutation
Induced mutation
Caused by transposable
genetic elements
mutations have no identifiable
cause and are rare.
Spontaneous mutations
mutations are due to chemical or
physical mutagens
Induced mutations
Induced mutations uses
UV light, nitrous acid,
base analogs etc.
Three major types of transposable elements
Insertion sequences
Transposons
Transposable phages (Mu)
They are segments of DNA that encode
enzymes for site specific recombination and
have distinct nucleotides at their terminals.
Insertion sequences
They are larger than insertion
sequences, code for protein
synthesis and can induce mutation
the same way as insertion sequences.
Transposons
They can alternate between lytic and
lysogenic growth. During lysogeny
Transposable phages (Mu)
They can insert themselves anywhere on the
bacterial chromosome, and later transpose from
one location to another, inactivating the
bacterial gene just as other transposable
elements.
Transposable phages (Mu)
Bacterial Recombination
Transformation
Conjugation
Transduction
Donor cells lyse, a fragment of DNA is released and passed
into a recipient cell.
Enzyme dissolves one strand of the fragment, and the other
strand displaces a homologous segment of the recipient’s
DNA.
The recipient then has a recombinant DNA.
The displaced fragment is dissolved by an enzyme.
Transformation
Only _____ can be transformed and DNA of both
organisms must be similar.
competent cells
is the ability to take up DNA from the
environment
Competence
It involves two live bacteria, donor and recipient,
with the transfer of genetic material from a plasmid.
Conjugation
The donor is F+, has fertility factor and codes for
sex pilus.
Once there is contact with the F - or recipient, plasmid DNA begins to replicate by the ______
Rolling
circle method
The transfer of genetic material from one organism
to another by a transducing phage.
Transduction
There are two types of transducing phages:
Lytic
Lysogenic
The phage reproduces and causes the bacterium
to lyse.
Lytic
This is a virulent phage.
Lytic
The phage codes for a repressor protein which
prevents its own replication.
Lysogenic
This is a temperate phage.
Lysogenic
There are two types of transductions
Generalized Transduction
Restricted or Specialized Transduction
A lytic virus uses the bacterial machinery to
make viruses.
☐The bacterium lyse and viral parts are
released.
Generalized Transduction
Only genes adjacent to the phage can be
transduced.
Restricted or Specialized Transduction
