2.4.1. Siderophore production
Siderophore production was determined according to the
methodology described by Schwyn and Neilands (1987). Actinomycetes
were streaked on chrome azurol S (CAS) agar media and
incubated at 28 2 C for four days. When the actinomycetes
consume iron, present in the blue-colored CAS media, orange halos
are produced around the colonies, which indicate the presence of
siderophores. Observations were recorded on a 04 rating scale as
follows: 0 ¼ no change; 1 ¼ positive; 2 ¼ halo zone of 1e3 mm;
3 ¼ halo zone of 4e6 mm and 4 ¼ halo zone of 7 mm and above..