Cytometry Review:
Probing the physiological state of phytoplankton at the single cell level
by
Frank J. Jochem
Scientia Marina (Barcelona), Vol. 64(2), June 2000, p. 183-195
ABSTRACT
Probing the physiological state of phytoplankton at the single-cell
level provides valuable insight in ecological 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. Photosynthetic 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 damage caused by UV-B radiation and to quantify diatom stickiness.
Fluorescein diacetate proved useful to discriminate metabolically active from
inactive cells and to reveal strategies of dark survival in algae. The activity
of alkaline phosphatase was recorded by a new fluorigenic substrate ELF, and
polyclonal antibodies against nitrate reductase (NR) provided measurements of
the NR abundance. An outlook will show how recent developments in molecular
probes might affect the future analysis of marine ecosystems and their
communities.
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