BackgroundActinomycetes may account for 10 to 30% of the totalsoil rhizosphere microorganisms. The attention given tothe actinomycetes in biotechnological applications is aresult of their metabolic versatility that is accompaniedby the production of primary and secondary metabolitesof economic importance, which are a promising source ofproducts (e.g., antibiotics, enzyme inhibitors, antiparasiticand anticancer agents) [1,2]. Included in this range ofcompounds are secondary metabolites synthesized bypolyketide synthase (PKS) and non-ribosomal peptidesynthetase (NRPS) pathways. An effective method forassessing the presence of these biosynthetic pathways isthe detection of PKS and NRPS genes by PCR [3,4].Thus, this study was based on targeted analyses of 31 soilisolate actinomycetes aiming to evaluate their antimicro-bial potential through the NRPS and PKS-I pathways.MethodsThe antimicrobial activity was evaluated by the antagon-ism test against two economically important phyto-pathogens, the bacterium Xanthomonas campestris andthe fungus Thielaviopsis paradoxa,usingthetechniqueof double layer. TheX. campestris and T. paradoxawere propagated at 28°C in YM (yeast malt) pH 6.0 andPDB (potato dextrose broth) respectively. The resultswere statistically analyzed using the Bonferroni test.The presence of genes PKS and NRPS was evaluatedby PCR, using degenerate primers for highly conservedregions encoding enzymes associated with biosynthesisof polyketides and peptides.Results and conclusionsAccording to the experimental results, 52% of the iso-lates showed antimicrobial activity against at least oneof the target bacterial pathogens tested. Among theseactive isolates, some belong to rare families. Thus, thisfinding can be a source of novel biomolecules with anti-microbial activity. From those isolates that presentedone of the NRPS and PKS-I genes, 75% of them showedantagonistic activity against one of the phytopathogensevaluated. Preliminary data on this screening demon-strate the importance of the biotechnological potentialof these actinomycetes due to the antagonistic activityagainst plant pathogens of economic interest and thepossibility of be used as biocontrol, besides offering astrong area for metabolic research [2,5].