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Micropara Lab (FINALS)
Exercise 7
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Elizabeth Cube
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Cards (12)
Some distinct characteristics of family Enterobacteriaceae:
gram
negative
bacilli
facultative
anaerobes
non-spore
forming
possess
fimbriae
and
flagella
pathogenic
antibiotic
resistance
genetic
plasticity
Different toxins produced by Enterobacters
hemolysin
cytotoxins
endotoxins
enterotoxins
siderophores
extracellular enzymes
antiphagocytic capsule
Citrate utilization
to differentiate
GNB
of
Enterobacteriaceae
also called
Simmon's citrate test
Simmon's
citrate agar
- contains
citrate
as main source of energy in the citrate utilization
Citrase
- breaks down citrate into
oxoloacetate
and
acetate
, where oxoloacetate is further broken down to form
pyruvate
and
carbon dioxide
Positive citrate
test -
shift in pH level
and
change in color
Methyl red test
detects the production of sufficient acid during fermentation of glucose
pH of an old culture is sustained below a value of about
4.5
In Enterobacters,
glucose
is converted to
pyruvic acid
and further metabolized to produce stable acid (
lactic acid,
acetic acid
,
formic acid
)
Positive MR test
- the color of methyl red changes from
yellow
to
red
Voges - proskauer test
used to determine if an organism produces
acetylmethyl
carbinol
from
glucose
fermentation
if present, it is converted into
diacetyl
in the presence of
alpha napthol
The
diacetyl
and
quanidine-containing compounds
are then condensed to from a
pinking red polymer.
K -
Alkaline
,
red
A -
Acidic, yellow