Thioglycollate Medium w/o Dextrose

Thioglycollate Medium without Dextrose is used for cultivation of aerobes, microaerophiles, anaerobes and for fermentation studies with various carbohydrates.

Composition**

Final pH ( at 25°C): 7.2±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 25.7 grams in 1000 ml distilled water. If the medium is to be used for fermentation studies or for diagnostic work adds 0.5 to 1% carbohydrate of choice. Heat to boiling to dissolve the medium completely. Dispense and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Alternatively, sterile carbohydrate solutions may be added to the broth after sterilization. The prepared medium should be stored in the dark at room temperature.

Note: If more than the upper one-third has acquired a green colour, the medium may be restored once by heating in a waterbath or free flowing steam until the green colour disappears.

Principle And Interpretation

Thioglycollate Medium without Dextrose is the modification of original Thioglycollate medium (1, 2) used for the fermentation study of anaerobes and for enhancement of sporulation. Omission of dextrose facilitates it to be used in fermentation studies with the addition of desired carbohydrate. Some Clostridia remain viable for a longer period and sporulate better in the absence of carbohydrate and thus this medium could be used for sporulations.

Casein enzymic hydrolysate, L-cystine and salts provide essential nutrients like nitrogenous compounds, carbon, sulphur, minerals and amino acids. The reducing action provided by sodium thioglycollate and sodium sulphite binds molecular oxygen, thereby maintaining a low Eh (3). A small amount of agar is added to retard the absorption of oxygen by reducing convection currents in the medium. Methylene blue is a redox indicator.

Quality Control

Appearance: Cream to yellow homogeneous free flowing powder

Colour and Clarity of prepared medium: Light yellow coloured very slightly opalescent viscous solution with upper 10% or less medium green on standing

Reaction: Reaction of 2.57% w/v aqueous solution at 25°C. pH : 7.2±0.2

pH: 7.00-7.40

Cultural Response

M190: Cultural characteristics observed after an incubation at 35-37°C for 48 hours(in an appropriate atmosphere).

Storage and Shelf Life

Store below 30°C and the prepared medium at 2-8°C. Use before expiry date on the label.

Reference

1. Brewer J. H., 1940, J. Am Med. Assoc., 115, 598.
2. Brewer J. H., 1940, J. Bacteriol., 39:10.
3. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol.1 William and Wilkins, Baltimore.