Geoscience Reference
In-Depth Information
Cells ml
-1
Cells ml
-1
0.1
100
100000
0.1
10
1000 00000
0
0
20
20
40
40
60
60
80
80
Depth
(m)
100
1
o
N
100
48
o
N
120
120
140
140
160
160
eMIT9313
eNATL2A
180
180
eMED4
eMIT9312
200
200
Figure 4.4. Depth distribution of different
Prochlorococcus
strains at 1
o
n and 48
o
in in the
Atlantic Ocean. redrawn from Johnson et al. (2006).
photosynthesis and carbon metabolism. Added to these are a total of
almost 6000 different variable genes shared by some but not all of the
different genomes. These give each different
Prochlorococcus
type its fla-
vor and determine how each is specifically adapted to its environment.
The function of many of these genes is unknown, so the specific details
of environmental adaptation are still fuzzy, but the message is clear.
Through gene swapping and gene evolution,
Prochlorococcus
has con-
structed “designer” genomes specifically adapted to the different envi-
ronmental conditions found in the oceans. ho needs a big genome
if you can ine-tune yours to the specifics of the environment? It is un-
known how widely this strategy is employed by microbes in nature, but
the recognition of
Prochlorococcus
genome flexibility by Penny and her
colleagues is, in my opinion, one of the big revolutions in modern ma-
rine microbiology.
As if making oxygen isn't enough, cyanobacteria also influence the
chemistry of the oceans in another critical way. To better understand
