Anescherichia colibioassay of individual siderophores in soil

A bioassay system using mutant strains of Escherichia coli K12 was developed which can detect four different types of siderophores. These types are: ferrichrome and its analogs; enterochelin; coprogen, rhodotorulic acid, and ferrioxamines A, B, D1, and G; and a group of unidentified chelators which forms a part of E. coli's high affinity iron transport system. The amount of the four siderophore types in concentrated water extracts of bulk and rhizosphere soil from a field sample was estimated using this bioassay.