lytic activity is alkaline egg medium which is prepared as follows: Mix the
56 MANUAL OF MICROBIOLOGICAL METHODS
yolk of one and the whites of two fresh eggs (preferably in a Waring
blender). Add 500 ml of distilled water, and adjust pH to 7.6. Stir
well, or mix in Cheap Seroquel
blender. Add 1 part of above to 5 parts of nutrient
broth, tube in deep columns, and sterilize for 20 min at 121C. The final
medium should be an opaque, whitish liquid. During growth proteolysis
is indicated by progressive clearing of the medium.
Nitrate broth. Add 0.1 per cent of KNO3 to a nutrient broth or agar.
For obligate anaerobes, also add 0.1 per cent of glucose and 0.1 per cent of
agar to basal medium and tube in deep columns. Cheap Seroquel
For organisms not
reducing nitrates in a peptone medium the following synthetic medium of
Dimmick (1947) is recommended: K2HPO4, 0.5 g; NaCl, 0.5 g; MgS04'
7H2O, 0.2 g; NaNOs, 2.0 g; glucose, 10.0 g; agar, 15 Cheap Seroquel g; distilled water
1,000 ml. If the organism being studied requires more calcium, add
0.05 g of CaCl2 to the above; in this case it is important that the final pH
be 7.2; to assure this after sterilization, adjustment before sterilization
should be to about 7.8.
Indole determination. Use 1 per cent concentration of a peptone high
in tryptophane, such as those prepared by enzymatic digestion of casein
or lactalbumin (see Chap. VII for methods of testing for indole).
H2S production. If the lead acetate paper tests recommended in
Chap. VII are not desired, use dehydrated media or consult the original
papers of Vaughn and Levine (1936), Cheap Seroquel
Hunter and Crecelius (1938), and
Untermohlen and Georgi (1940) for directions for preparation of media
containing lead, bismuth, or iron salts which will precipitate as the
sulfides in the presence of II2S.
Methyl red and Voges-Proskauer reaction. Prepare basal medium
for these tests as follows: peptone, 7.0 g; glucose, 5.0 g; K2HPO4, 5.0 g.
Since all peptones are not suitable, use for peptone an enzymatic digest of
casein. For details concerning these reactions consult Chap. VII.
Medium for determination of utilization of citrate. Within the gram-
negative nonsporef orming bacilli, differentiation of Cheap Seroquel
some types is based on
utilization of citrate as the sole source of carbon. Koser's synthetic
medium is suitable for this and is prepared as follows: KH2PO4, 1.0 Cheap Seroquel g;
MgS04, 0.2 g; NaNH4P04, 1.5 g; NaaCeHBOy, 3.0 g; water, distilled,
1 liter. Growth, as evidenced by turbidity, in the water-clear medium
indicates utilization of the citrate radical Cheap Seroquel
as a carbon source. One should
make certain that a small enough inoculum is used in this medium so that
it is not noticeably turbid before incubation. This can be accompHshed
by using a straight needle for inoculation or by using a loopful of a sus-
pension in sterile water.
Litmus milk. Prepare saturated aqueous solution of litmus. Add a
sufficient quantity of the solution to give a light lavender color to fresh
skimmed milk (some grades of dried milk powder may be substituted, but
PREPARATION OF MEDIA 67
many are unsatisfactory); sterilize 12-15 min at 120C; cool tubes
immediately by immersing in Cheap Seroquel
cold water. For anaerobic organisms,
Spray's system of classification is based upon use of this medium (tubed
in a deep column) to which is added 0.05 g Cheap Seroquel
of reduced iron or a thin strip
of iron. The reactions determined for aerobic bacteria on this medium
are explained in Chap. VII; those for anaerobes in Spray's (1936) original
Pigment production. This character may be observed on a variety of
media, and reports describing characteristics of new species should indicate
the medium used. Starch agar (as described above) is often satisfactory,
and if the organism will grow on potato slants, this medium may be used.
Potato slants are prepared as follows: Peel white potatoes and cut plug
from center, using cork borer of appropriate size. Slice plugs obliquely
to make slants. Wash slants overnight in slowly running cold tap water.
Place plugs in tube supporting them with small glass rod, stick of wood,
or potato slice; add 1 ml of water to keep slants moist during incubation,
and sterilize. Pigment production by Clostridia may be observed in
corn-meal infusion medium (page 49) prepared without addition of liver
or in potato infusion.
Lipolysis. For media to be used to detect Hpolytic action and for
methods of proper preparation of fat emulsions, consult the papers of
Castell (1941), Castell and Bryant (1939), Collins and Hammer (1934),
Eisenberg (1939), Knaysi (1941), and Starr (1941).
MEDIA FOR SPECIFIC BACTERIOLOGICAL PROCEDURES
In the preceding sections a variety of media have been presented which
are suitable for the isolation, cultivation, characterization, and mainte-
nance of bacteria. Many of these media can be employed for multiple
purposes, and conversely, in some instances, several different formula-
tions may prove satisfactory for the same purpose. The established per-
formance of a medium and the personal preference of the laboratory
worker result in the adoption of one formula in place of another.
However, there are numerous bacteriological procedures which require
that media of a designated composition be used. Listed in Table 3 are
several such microbiological procedures, together with references which
specify the composition of media required for performance of the tests.
MEDIA FOR SPECIAL PURPOSES
Voluminous experimental evidence attests to the fact that the composi-
tion of the culture medium has a profound influence on the microbial cell
with respect to formation of enzymes, toxins, antibiotics, and other
58 MANUAL OF MICROBIOLOGICAL METHODS
products. Some aspects of this subject have been reviewed by Gale
(1951). A few examples are presented below.
Metabolically active cells. In many studies dealing with the physio-
logical activity of cells harvested from culture media, comparatively little
attention has been paid to the conditions of growth, a large cell crop being
the usual criterion of the adequacy of the medium. Wood and Gunsalus
(1942) have pointed out the limitation of this criterion and have studied
the effects of the components of the growth medium upon the dehydro-
genase activity of suspensions of Cheap Seroquel Streptococcus mastitidis. A Cheap Seroquel
easily prepared medium was described consisting of the following ingredi-
ents: 'Hryptone," 10 g; yeast extract, 10 g; K2HPO4, 5 g; glucose, 2 g;
water, 1 liter. Metabolically active cells were obtained after incubation
at 37C for 12-15 hr. The final pH was about 6.8. Tsuchiya and
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