Isolation and characterization of Azotobacter chroococcum from the roots of Zea mays

Abstract

Bacteria showing rapid growth on a nitrogenfree medium and acetylene-reducing activity were isolated from maize roots collected from agricultural soils in Spain. The isolates were Gram-negative motile rods and were identified as Azotobacter chroococcum. Acetylene-reducing activity and microbial counts were determined on root segments from 7- and 30-day-old plants. Rates obtained were in the range of 0.0053–0.848 nmol C 2H 2 · g −1 · h −1. Root populations were 1.4–6.0 × 10 4 micro-organisms · g −1. These results showed that there was an association between A. chroococcum strains and roots of maize planted in some Spanish soils.