Modified combined carbon N-deficient medium for isolation, enumeration and biomass production of diazotrophs

Dinitrogen fixation associated with non-legumes has been well documented (Dobereiner, 1983; Hegazi, 1983; Fayez, 1990) and is now generally considered to make a significant contribution to the nitrogen economy of several ecosystems. This intensifies the use of field inoculation with various diazotrophs. Therefore, the need arises to monitor the populations and individuals of several associative diazotrophs inhabiting the plant-soil system. The ability of several diazotrophs to multiply and reduce acetylene on numerous carbon sources encourages the search for a single medium suitable for collective growth and biomass production of a number of diazotrophs. The present study evaluates a new medium modification based on basal salts and a mixture of five carbon sources (glucose, malic acid, mannitol, sodium lactate and sucrose) to fulfil the requirements for a single medium on which the majority of associative diazotrophs would exhibit good growth and biomass production.