Two species-specific TaqMan-based quantitative polymerase chain reaction assays for the detection in soil of Paenibacillus polymyxa inocula

Aims: The increasingly widespread use of beneficial microbial inocula in agriculture gives rise to two primary needs: i) the assessment of the environmental risk, i.e. their impact on local soil microbiome and soil properties; ii) being able to track them and monitor their persistence and fate to both optimize their formulation and application method. In previous years, PCR-based methods have detected bacterial or fungal bioinoculant at the species or strain level. However, the selective detection, quantification, and monitoring of target microbial species in a complex ecosystem such as soil require that the tests possess high specificity and sensitivity. Methods and Results: The work proposes a quantitative real-time PCR detection method using TaqMan chemistry, showing high specificity and sensitivity for the Paenibacillus polymyxa K16 strain. The primer and probe sets were designed using the polymyxin gene cluster targeting pmxC and pmxE sequences. Validation tests showed that these assays allowed a discriminant and specific detection of P. polymyxa K16 in soil. Conclusion: The TaqMan-assay developed could thus ensure the necessary level of discrimination required by commercial and regulatory purposes to detect and monitor the bioinoculant in soil.