HIGH SURVIVAL EFFICIENCY AND RIBOSOMAL-RNA DECAYING PATTERN OF DESULFOBACTER-LATUS, A HIGHLY SPECIFIC ACETATE-UTILIZING ORGANISM, DURING STARVATION

Exponentially grown Desulfobacter latus cells were transferred to anae robically prepared minimum medium without a carbon or energy substrate and incubated under anaerobic conditions. Changes in 16S ribosomal RN A (rRNA) of individual cells and the viable fraction in a population w ere monitored. The cell preparation was stained with a phylogenetic DN A probe labelled with fluorescent dye and the fluorescence of each cel l was determined with confocal scanning laser microscope. Viable cells were defined as those capable of reducing a tetrazolium salt (the INT method [1]). The viability of a Desulfobacter starvation culture decr eased to 85% in 48 h, but further decrease was not observed during pro longed starvation. The mean amount of 16S rRNA in individual cells dec reased exponentially for 48 h to 30% the mean value obtained for expon entially growing cells, but did not decrease by prolonged starvation. About 30% of the mean content of 16S I RNA in growing cells was found in the starved cell population, suggesting that most individual cells in the starved population were not metabolically active. The differenc e between gross pixel intensity of cells having < 8% of 16S rRNA in gr owing cells and those with a negative control probe was not significan t. Thus, non-viable cells may not show positive signals by phylogeneti c staining.