A new approach to isolating siderophore-producing actinobacteria

Aims: The current study was conducted to investigate the application of 2, 2’- dipyridyl as a new approach to isolating siderophore producing actinomycetes. Methods and Results: Isolation of actinomycetes from soil was conducted by a soil dilution plate technique using starch-casein agar. Iron starvation was fostered by the incorporation of the iron chelator 2, 2’-dipyridyl in the isolation medium. Pretreatment the samples at an elevated temperature (400 33 C) ensured that the majority of non-sporulating bacteria were excluded. The survivors of this treatment were largely actinomycetes. Of the viable cultures grown in the presence of 2, 2’-dipyridyl, more than 78-88 % (average of three separate studies) were reported to produce siderophore like compounds compared to 13- 18% (average of three separate studies)when grown on the basic media in the absence of the chelating agent. The most prolific producers as assessed by the Chromo Azuerol Sulphate (CAS) assay were further characterised and found to belong to the genus Streptomyces. Conclusions: Selective pressure using 2, 2’-dipyridyl as an iron chelating agent I starch-casein media increased the isolation of siderophore producing actinomycetes compared to the unamended medium. Significance and Impact of the Study: The study described represents a new approach to the isolation of siderophore producing actinomycetes using a novel procedure that places a selection on cell population based upon the incorporation of a chelating agent in the medium