New selective media for enumeration and recovery of fluorescent pseudomonads from various habitats.

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%).