Grape juice agar

Metal spatulas. 8. Yeast Paste. 9. 100% Bleach. 10. Grape juice agar medium for embryo collection 227.5 mL grape juice, 43.5 g sucrose, 11 g Agar 5 mL of an 1.25 N NaOH solution, 5.5 mL acid mix (418 mL propionic acid, 41.5 mL 85% phosphoric acid, distilled H20 to make 1 L) (see Note 3). 

Shake 200-400 flies from a culture vessel into a 250 mL plastic beaker and cover with a grape juice agar plate containing a small drop of yeast paste. Place it upside down so flies will lay their eggs on the grape juice (see Note 5). 

Used as a nonselective general growth medium for wine and juice microorganisms, grape juice agar is prepared as follows ... 

General growth media (YM, malt, grape juice agar)... 

Numerous media are used for the isolation, detection, and/or enumeration of yeasts from grape juices and wines. Wort medium is non-selective for yeast and is commonly used to enumerate Saccharomyces (King and Beelman, 1986). An incubation period of 2 to 4 days at 22°G/72°F to 25°C/77°F is needed for colonies to appear. Similarly, grape juice agar is non-selective and will support the growth of many yeasts, bacteria, and molds. 

When determining how many embryo collection trays to prepare, consider the following (1) An active fly house must always contain a collection tray for collections and to keep the flies well-fed between collections (2) trays can be rinsed with warm tap water and reused once for noncollection, feeding periods and (3) the shelf-life of the media at 4°C (several months for grape juice agar). It is usually a good idea to prepare more trays than may be needed. A 25.7 x 20.6-cm tray requires about 150 ml of e -laying media. 

Mix the agar and grape juice solutions together once each has cooled to 70 C. Allow the Grape Juice-Agar solution to sit, allowing bubbles to rise. 

Grape juice-agar plates and yeast paste for embryo collection (see Sisson, this volume)... 

Collect embryos on grape juice-agar plates and wash them into baskets using H O and a soft brush. JCeep the embryos in the basket for subsequent steps until fixation. Rinse the embryos well with H O to remove yeast. 

Before meaningful identification work can begin, it is necessary to collect the suspect yeast into a pure culture. General growth media for yeast include nutrient, grape juice, wort, malt, and yeast and mold (YM) extract agar. With the exception of grape juice, these are commercially avail-... 

Successful cultivation of microorganisms for growth and identification requires use of various types of media, either liquid (referred to as hroths) or solid by inclusion of agar. For winemakers, a growth medium may he as simple as diluted sterile grape juice for the activation and expansion of yeast starter cultures or as complicated as that necessary to grow lactic acid bacteria. 

Standard grape or apple juice agar plates (see Appendix 3)... 

Transfer a small cluster of embryos onto a new, small grape or apple juice agar pad ( 5 X 10 X 2 mm, cut from a grape or apple juice plate), and then use a metal probe or a sharpened wooden applicator stick to align them on the edge of the pad. 

Notes Surface tension from the moist grape or apple juice agar holds the embryos gently in place, so that they can be oriented easily with respect to dorsal/ventral and anterior/posterior. 

Add 3 g of Bacto Agar (Difco) to 50 ml of HjO in a 200-ml beaker. Place the beaker in a microwave oven to dissolve the agar. Add 50 ml of prewarmed (60°C) fruit juice (grape or mango punch, any will probably work), 1 ml of a 10% solution (w/v) of methyl-P-hydroxy benzoate (Sigma H 6654) in ethanol, and 1 ml of glacial acetic acid. Pour into petri plates or collection dishes of choice to a depth of approximately 5 mm. The volumes can be scaled up as needed. 

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