Indole production This is recorded after 7 days incubation in 1 wv peptone

Indole production this is recorded after 7 days

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Indole production This is recorded after 7 days incubation in 1% (w/v) peptone water. For mar- ine organisms, this should be prepared MSS (2.4% [w/v] NaCl; 0.7% [w/v] MgS04. 7H2O; 0.075% [w/v] KCl; after Austin et al, 1979). A positive response is indicated by a red coloration following the addition of a few drops of Kovacs reagent. a-Galactosidase production One of the most reproducible methods is to record a-galactosidase production from the API-zym system after incubation for 48h at 15 or 25°C. P-Galactosidase production This involves use of the medium of Lowe (1962). Inoculated medium is incubated for 7 days, whereupon a positive response is indicated by a yellow coloration. For marine organisms, the medium should be prepared in MSS. Production of arginine dihydrolase and lysine decarboxylase We recommend use of the medium described by Moller (1955). Essentially, inocu- lated medium is incubated for 7 days, when a positive reaction is indicated by a purple coloration. With marine organisms, the medium should be prepared in MSS. Urease production Using the medium of Stuart et al. (1945), a positive response develops as a reddish coloration within 28 days. For marine organisms, it is suggested that the medium is supplemented with 2.4% (w/v) sodium chloride.
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234 Bacterial Fish Pathogens Methyl red test and Voges Proskauer reaction These may be recorded after 7 days incubation in MRVP broth (Difco). Following the addition of a few drops of methyl red, a bright red coloration indicates a positive methyl red test. The Voges Proskauer reaction is recorded after use of commercially available reagents. A positive reaction is indicated by a red coloration which develops within 18 h (usually within 1 h) after the addition of the reagents. As before, with marine organisms the medium may be prepared in MSS. Degradation of blood This should be recorded within 7 days as zones of clearing around colonies on basal medium supplemented with 5% (v/v) defibrinated sheep's blood. Degradation of gelatin This is detected after 7 days incubation by the addition of saturated ammonium sulphate solution to the medium of Smith and Goodner (1958). A positive result is indicated by zones of clearing around the bacterial growth. For marine organisms, the medium should be supplemented with MSS. Degradation of starch Basal medium supplemented with 1 % (w/v) soluble starch is streaked, and incubated at 15-25°C. After 7 days, the starch plates are flooded with an iodine solution (e.g. Difco Gram's iodine). The degradation of starch is indicated by a clear area surrounded by a blue/black background. Acid production from maltose and sorbitol The use of Andrade or phenyl red-peptone water supplemented with maltose or sorbitol is advocated (see Cowan, 1974). This medium contains 1% (w/v) bacterio- logical peptone 0.5% (w/v) sodium chloride (for marine organisms this amount should be increased to 2%), 1% (w/v) maltose and Andrade or phenyl red indicator.
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  • Spring '20
  • Bacteria, representative, gram-negative bacteria

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