2. Apparatus
a. Incubation bottles: Use glass bottles having 60 mL or
greater capacity (300-mL bottles having a ground-glass stopper
and a flared mouth are preferred). Clean bottles with a detergent,
rinse thoroughly, and drain before use.
b. Air incubator or water bath, thermostatically controlled at
20 1°C. Exclude all light to prevent possibility of photosynthetic
production of DO.