FIG. 1.

Specificity of 16S rRNA-targeted probes used in this study and the detection sensitivity of a typical probe (UNIV 342) applied for the detection of membrane blotted cells. (A) The specificity of each of the probes used in this study was determined by hybridization at 37°C for the universal eubacterium-targeted probe UNIV and at 55°C for the SRB group-specific probes (SRB 687, 660, 814, 129, 221). RNA (2 ng/slot) purified from cultures of Desulfovibrio desulfuricans ATCC 13541 (DSV), Desulfobulbus propionicus ATCC 33891 (DSB), Desulfococcus multivorans ATCC 33890 (DSC), Desulfobacter sp. strain BG-8 (DBACTER [30]), and Desulfobacterium sp. strain BG-33 (DSBM [30]) were immobilized on replicate charged nylon membranes and hybridized with each probe used in this study. (B) Hybridization sensitivity of a 16S rRNA-targeted probe (UNIV 342) for the detection of immbolized D. desulfuricans cells. Hybridization signal was proportional (r² = 0.90) to the number of cells. Hybridization detection is expressed in relative optical density (OD) units. Autoradiograph of replicate whole-cell hybridization used to construct the regression line is shown below the regression line.