Enumeration and Cell Cycle Analysis of Natural Populations of Marine Picoplankton by Flow Cytometry Using the Nucleic Acid Stain SYBR Green I

TLDR

SYBR Green I specifically binds nucleic acids and is excitable by blue light at 488 nm. Using SYBR Green I on a low‑cost flow cytometer, cell concentrations of marine prokaryotes matched those obtained with Hoechst 33342 on a high‑end instrument, while the dye also clearly discriminated heterotrophic bacteria and autotrophic Prochlorococcus cells, distinguished two bacterial subgroups, and provided DNA‑distribution resolution sufficient to analyze the cell cycle of photosynthetic prokaryotes throughout the water column.

Abstract

The novel dye SYBR Green I binds specifically to nucleic acids and can be excited by blue light (488-nm wavelength). Cell concentrations of prokaryotes measured in marine samples with this dye on a low-cost compact flow cytometer are comparable to those obtained with the UV-excited stain Hoechst 33342 (bis-benzimide) on an expensive flow cytometer with a water-cooled laser. In contrast to TOTO-1 and TO-PRO-1, SYBR Green I has the advantage of clearly discriminating both heterotrophic bacteria and autotrophic Prochlorococcus cells, even in oligotrophic waters. As with TOTO-1 and TO-PRO-1, two groups of heterotrophic bacteria (B-I and B-II-like types) can be distinguished. Moreover, the resolution of DNA distribution obtained with SYBR Green I is similar to that obtained with Hoechst 33342 and permits the analysis of the cell cycle of photosynthetic prokaryotes over the whole water column.