Geoscience Reference
In-Depth Information
contain cyanobacteria, but take a close look at the rock itself. Living at,
and especially just beneath, the surface of this natural sandstone sculp-
ture are abundant populations of cyanobacteria. Travel to the Dry Val-
ley regions of Antarctica, and you will find something similar in the
giant cliffs of the Beacon Sandstone facing Lake Vanda in Wright Val-
ley. Sandstone and granite outcrops containing cyanobacteria are found
in other arid and semiarid environments ranging from North Transvaal,
South Africa, to the Orinoco lowlands of Venezuela.
Let's look in the oceans. Scientists have studied marine algae for cen-
turies. Yet, there's no mention of cyanobacteria in Claude Zobell's clas-
sic treatise
Marine Microbiology
from 1946, nor were marine cyanobacteria
described in the biological oceanography textbook that I used in 1980.
In fact, by the time my biological oceanography textbook was written
(1977), bundle-forming cyanobacteria of the genus
Trichodesmium
had
been described (more on these interesting organisms below), and other
small coccoidal-shaped cyanobacteria had also been identified; but ap-
parently their novelty was such that they had not yet entered into text-
book discussions. The situation changed in 1979 when John Waterbury
from the Woods Hole Oceanographic Institution, along with colleagues,
described the widespread abundance of tiny marine cyanobacteria of
the genus
Synechococcus
. And as it turns out, these little guys are common,
except in high Arctic regions, with abundances ranging up to one mil-
lion cells per liter of ocean water.
How could they have been so long overlooked? For decades, marine
phytoplankton (which are photosynthetic plankton) had been collected
for study in nets with mesh sizes of about 20 microns (0.02 mm). How-
ever,
Synechococcus
cells are tiny, with diameters ranging from about 0.8
to 1.5 microns. Therefore, net as many phytoplankton as you like, and
Synechococcus
cells will just wash through the net. But, John collected
cells on filters with much smaller pore sizes (0.2 microns) and was thus
able to isolate these tiny
Synechococcus
cells. As often occurs in scientific
discoveries, however, John was not looking for cyanobacteria at all, but
for something completely different. He was instead using a new tech-
nique to quantify total bacterial cell numbers by staining the cells with
a fluorescent dye and counting them under a microscope as they fluo-
resced under blue light. A good scientist makes controls (samples that
are not treated), and John saw immediately that some cells fluoresced
