Phytopatogenic bacteria cause several damages to plants with
important economical consequences. They provoke losses of product quality affecting all commercial
chain of crops, for this reason, their control is a priority. Approach: We evaluated antagonist capacity
of newly isolated Pseudonomas fluorescens strains against three important phytopatogenic bacteria
(Clavibacter michiganensis, Xanthomonas axonopodis and Erwinia carotovora). Soils from
commercial cropping of Capsicum annum L of several Mexican regions were used to isolate P.
fluorescens strains. Results: Isolates producing flourescein were purified on King B agar and
biochemically identified. Crude extracts with and without cells were produced in King B broths and
their antagonist capacities were evaluated by the plate diffusion procedure on nutritive agar.
Conclusion: Obtained results demonstrated that cell free extracts exhibited a limited antagonist
capacity in comparison of those extracts with cells, which showed an excellent capacity to inhibit the
growth of C. michiganensis, X. axonopodis and E. carotovora, demonstrating the intracellular nature of
the bioactive metabolites associated to bacterial growth inhibition.
Key words: Pseudonomas fluorescens, ellular nature, Mexican agriculture