Examination of Gould’s modified S1 (mS1) selective medium and Angle’s non-selective medium for describing the diversity of <i>Pseudomonas</i> spp. in soil and root environments

Studies on the diversity of environmental culturable <i>Pseudomonas</i> populations are dependent on the isolation procedure. This procedure includes the use of selective media which may influence the recovery of strains and thus the diversity described. In this study, we assessed the use of two agar isolation media for describing the diversity of soil- and root-inhabiting <i>Pseudomonas</i> associated with the perennial grass <i>Molinia coerulea</i>. A total of 382 <i>Pseudomonas</i> strains were recovered on either non-selective Angle’s medium, or on Gould’s modified S1 (mS1) <i>Pseudomonas</i>-selective medium. Their diversity was assessed by restriction analysis of PCR (polymerase chain reaction)-amplified 16S–23S rDNA internal transcript spacer sequences. The comparison of mS1- and Angle-recovered populations showed that the use of mS1 selective medium led to an underestimation of both <i>Pseudomonas</i> counts and diversity, especially in the soil environment.