(^) Waterbury et al. and Johnson and Sieburth both reported in 1979 that very large
numbers of photosynthetic bacteria can be counted in water samples from the ocean.
These bacteria had been overlooked previously for several reasons, principally that
they are small, all under 2 μm and most about 1 μm in diameter. Cyanobacterial
thylakoids (Fig. 2.1) include alternate layers of phycobilisomes, particles of protein
binding photosynthetic accessory pigments including phycoerythrin. This pigment has
a characteristic orange fluorescence in blue light that is strong enough to mask the red
fluorescence of chlorophyll. This makes cyanobacteria readily countable with an
epifluorescence microscope, an important tool in the study of this group’s ecology
(see Box 2.2).
Fig. 2.1 Morphological plans of (above) single-celled cyanobacteria (Synechococcus)
and (below) Prochlorococcus marinus.
(^) (After Van den Hoek et al. 1995.)
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