There are numerous reports of the production of antibiotic compounds by Pseudomonas spp. Some of these antibiotics have been characterized chemically ( Leisinger and Margraff 1979). Howell and Stipanovic, 1979 and Howell and Stipanovic, 1980 provided evidence that different isolates of P. fluorescens were antagonistic to pathogens of cotton seedlings because of the production of the antibiotics pyrrolnitrin and pyoluteorin. Another antibiotic, produced by a Pseudomonas strain that was able to suppress take-all in wheat, was identified as a dimer of phenazine-1-carboxylate ( Gurusiddaiah et al. 1986). Lam et al. (1987) reported a Pseudomonas isolate that produced an unidentified antibiotic able to inhibit the fungus that causes Dutch elm disease.