《5 Probing the physiological state of phytoplankton at the single-cell level》.pdf

SCI. MAR., 64 (2): 183-195 SCIENTIA MARINA 2000 AQUATIC FLOW CYTOMETRY: ACHIEVEMENTS AND PROSPECTS. M. RECKERMANN and F. COLIJN (eds.) Probing the physiological state of phytoplankton at the single-cell level* FRANK J. JOCHEM The University of Texas at Austin, Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, USA. Fax: (361) 749 6777. E-Mail: frank@emcs.de SUMMARY: Probing the physiological state of phytoplankton at the single-cell level provides valuable insight in ecologi- cal studies as well as in environmental monitoring of pollution or UV impacts. This paper reviews the recent progress in assessing the physiological state of phytoplankton with flow cytometry by inherent cell properties such as cell size and chlorophyll autofluorescence, specific fluorescent dyes, and newly developed molecular probes and enzyme substrates. It is reported how nitrogen and iron limitation as well as the effect of copper pollution could be derived from changes in cell inherent properties. Effects of Cu were also recorded by monitoring cell membrane potentials and esterase activity. Photo- synthetic capacity of algae was assessed by changes in chlorophyll fluorescence with the electron transport inhibitor DCMU, by a cytometric adaptation of the pump-and-probe approach, and molecular probes for Rubisco. Antibodies were also applied to mark non-terminal stages in the cell DNA replication cycle, to detect non-proliferating cells, to assess DNA dam- age caused by UV-B radiation and to quantify diatom stickiness. Fluorescein diacetate proved useful to discri