[Use of automated image analysis for screening the efficiency of turimycin-producing Streptomyces strains]

The growth of the surface colonies on solid media is studied with the image analyzing system Quantimet 720 M controlled by a PDP 11 computer. For the bacterial strain Streptomyces hygroscopicus JA 6599 a new differential equation describing the kinetic behaviour of the area of the colony is suggested. It is shown that this time dependence of area describes more realistically the experiment than the function resulting from Pirt's model. Two new constants arise from the growing curve, alpha describes the profile of density of the colony and k0 is correlated to the growing constant of the colony. Both parameters can be correlated to the amount of antibiotics produced and, therefore, it is possible to use this information for the selection procedure of the colonies. A uniform criterion for selection was found for each colony of two mutants of the turimycin-producing strain Streptomyces hygroscopicus JA 6599, which reads: (Formula: see text). The quality of the selection criterion of surface colonies with higher productivity is dependent on the mean value of the growing parameters of all colonies under investigation. Limitations of the selection method arise from the need for great uniformity of environmental conditions, growth medium and a homogeneous spore suspension, which have to consist of a large amount of single spores in order to assure a reproducible growing curve of the colonies. For the last condition a special technique is pointed out.