New Selective Media for Enumeration and Recovery of Fluorescent Pseudomonads from Various Habitats

Abstract

New media (S1 and S2) were formulated that provide a high degree of selectivity and detection of fluorescent pseudomonads on initial plating. The selectivity of the S-type media was based on a detergent, sodium lauroyl sarcosine, and an antibiotic, trimethoprim. A total of five soils from different geographical locations and one sewage sludge sample were examined. On S1 medium, isolates from two soils with low fluorescent pseudomonad populations exhibited a high frequency of arginine dihydrolase (78%) and oxidase-positive (95%) phenotypes, but no fermentative isolates were recovered. Medium S2 was more defined and selective than S1, but lower numbers of fluorescent pseudomonads were recovered on S2. In soils in which fluorescent pseudomonads represent a small proportion of the total population, S1 medium consistently recovered high percentages of fluorescent phenotypes (82.5%).

Glyphosate affects micro-organisms in rhizospheres of glyphosate-resistant soybeans

“…A 1-g portion of rhizosphere soil from each sample was suspended in 0AE01 mol l )1 MgSO 4 buffer, and appropriate 10-fold dilutions were plated on S1 agar medium selective for fluorescent pseudomonads (Gould et al 1985) and on Gerretsen's agar medium for detecting Mn-oxidizing and Mn-reducing micro-organisms (Huber and Graham 1992). After incubation at 25°C (48 h for pseudomonads; 7 day for Mn-transforming bacteria), colonies developing on agar medium were recorded as colony-forming units in the rhizosphere.…”

Maize heterosis affects the structure and dynamics of indigenous rhizospheric auxins-producing Pseudomonas populations

“…The Pseudomonas population analysed in this study was the same previously isolated on S1 medium [30] from each of the three maize genotypes, and which was previously screened for DAPG production [6]. Briefly, Pseudomonas isolates were from rhizospheres of the three maize genotypes collected from both trials, at three stages of plant growth, corresponding to the end of germination (Eg, 27 days after planting), the end of flowering (Ef, 72 days after planting) and the physiological maturation (Pm, 106 days after planting).…”

Frequency and biodiversity of 2,4-diacetylphloroglucinol-producing rhizobacteria are differentially affected by the genotype of two maize inbred lines and their hybrid

“…In order to get representative samples for data comparison among plant genotypes, the same quantity (fresh weight) of each type of roots was collected from each individual plant. Serial dilutions were plated onto solid S1 medium, which is known to be selective for the recovery of fluorescent pseudomonads [21]. The plates were incubated at 27°C, numbers of cfu were determined after seven days and reported per gram of dry roots.…”