DNA distributions in planktonic bacteria stained with TOTO or TO‐PRO

Abstract

The blue-excitable nucleic acid-binding fluorochromes, TOT0 and TO-PRO, were used to stain bacteria in marine plankton communities. Flow cytometric counts of cells stained with these dyes agreed well with counts made by epifluorescence microscopy of DAPI-stained cells. We have used these new dyes in a study of bacteria from various waters in the North Atlantic and the eastern Mediterranean. The results indicate a distinction among bacterial groups of different fluorescence intensities (apparent DNA content). At large spatial and temporal scales, about half of the variation in the percentage of bacteria with high apparent DNA content (termed group II bacteria) could be explained by the variation in chlorophyll. Further, the apparent mean DNA content of group II bacteria was also correlated with chlorophyll.

Morphology and DNA content of bacterioplankton in the northern Gulf of Mexico: analysis by epifluorescence microscopy and flow cytometry

“…Cluster B-III corresponds to B-III of Marie et al (1997), which was not detected by Li et al (1995). A cluster termed B-II by Li et al (1995) and Marie et al (1997), distinguished by higher DNA content but lower light scatter than that of B-I, was not detected. Instead, a high DNA content and light scatter cluster, indicating larger cell size (B-IV), occurred.…”

“…Coccoid bacteria averaged 0.42 µm in diameter (0.04 µm 3 cell volume) but comprised both Li et al (1995) and Marie et al (1997) in samples from the North Atlantic, the Mediterranean and the English Channel. Cluster B-III corresponds to B-III of Marie et al (1997), which was not detected by Li et al (1995).…”

“…Coccoid bacteria averaged 0.42 µm in diameter (0.04 µm 3 cell volume) but comprised both Li et al (1995) and Marie et al (1997) in samples from the North Atlantic, the Mediterranean and the English Channel. Cluster B-III corresponds to B-III of Marie et al (1997), which was not detected by Li et al (1995). A cluster termed B-II by Li et al (1995) and Marie et al (1997), distinguished by higher DNA content but lower light scatter than that of B-I, was not detected.…”

“…Despite significant progress in molecular biology, most of these techniques are still in their developmental phase, sometimes difficult to quantify and too laborious for application in extended field surveys (Collier & Campbell 1999). DNA staining in combination with flow cytometry has now been introduced to differentiate and quantify subpopulations of bacteria with different apparent DNA content and to reveal their distribution patterns and ecological significance (Li et al 1995, Marie et al 1997, Casotti et al 2000.…”

“…Phototrophic prokaryotes, Prochlorococcus spp. and Synechococcus spp., can be distinguished from heterotrophic bacteria by their chlorophyll autofluorescence in cytometric analyses (Li et al 1995, Marie et al 1997, Gasol & del Giorgio 2000.…”