have sequenced for the first time, genomes of
bacteria that live in the sea. The microbes belong
to cyanobacteria group, says Donald Bryant of
Pennsylvania State of University. They account
for roughly half of the photosynthesis in the
oceans. They remove about 10 billion tons of carbon
from the air.
Sallie Chisholm of the Massachusetts Institute
of Technology and his team sequenced Prochlorococcus
marinus, the most abundant photosynthetic.
Its strongholds are the tropical and temperate
oceans; it is less common in polar waters and
close to land. Prochlorococcus is short
on genes that would help it respond to environmental
changes. The other species sequenced,
Synechococcus, has a larger genome
and is less abundant at 10,000 cells per ml
of seawater but is more widely distributed.
The genome of Synechococcus shows that
it can process a wider range of chemicals than
Prochlorococcus. Some of its enzymes
are adapted to breakdown nickel and cobalt,
probably as a way of conserving iron, which
is in short supply in the sea, and it can use
several different sources of nitrogen.