Effect of Antibiotic and Chemical Dips on the Microflora of Packaged Salad Mix

SALAD MIX lyophil process, with soil stocks, or the sterile mineral oil method, and yet the advantage of storage under deep metabolic repression is enjoyed.Also, a relatively large collection of organisms can be stored in a small space without the problem of drying or contamination if small screwcap tubes or vials are employed.Experiments are now in progress which indicate that deep-freeze storage of true bacteria by the same Car- michael method may also be useful.In view of the great range of microorganisms which can be successfully maintained by this method, and the general availability of equipment of various capacities, we feel that deepfrozen storage offers a useful addition to the existing armamentarium of culture preservation methods. SUMMARY A collection of about 400Streptomyces cultures, in- cluding members of some 135 described species, has been stored in deep freeze (-22 C) as an auxiliary long- term maintenance method.About 60 per cent of these were frozen for more than 3 years, the remainder for varying periods up to 3 years.In annual checks, viability was observed to be exceptionally good, and, so far as could be ascertained, none of the original cultural or morphological features had undergone modification.Antibiotic-producing capacity of 16 cultures was found to be essentially unchanged after 2 years' storage.