Characteristics of Bacteria Requiring the Terregens Factor

Six organisms belonging to the genus Arthrobacter and showing a requirement for the terregens factor (TF) have been studied and compared with the original test organism, Arthrobacter terregens. All seven organisms are alike in that they are stimulated not only by the terregens factor but also by certain related substances that contain iron, namely coprogen, ferrichrome, and hemin. TF response is also obtained with aspergillic acid, soil extract, and liver extract. On the basis of their physiological characteristics and nutritional requirements, the organisms were grouped into four types. Growth curves of A. terregens and one other organism, based on response to TF, suggest their suitability for use in the microbiological assay of the factor.