Biology Reference
In-Depth Information
into biomass in the field at greater efficiencies (3-9%) than terrestrial plants
(0.25-3%), and they tolerate higher CO
2
content in gas streams than plants
(
Ducat, Way, & Silver, 2011
). On a global scale, cyanobacteria fix an esti-
mated 25 Gt of carbon from CO
2
per year into energy-dense biomass.
Hence, cyanobacteria are regarded as promising 'low-cost' microbial cell
factories for the capture and storage of industrial CO
2
gas (
Jansson &
Northen, 2010
), and the ecologically responsible production of biofuels
(
Ducat et al., 2011
;
Zhou & Li, 2010
). Moreover, cyanobacteria also have
the potentials for the biotechnological production of natural products and
secondary metabolites (
Pearson, Mihali, Moffitt, Kellmann, & Neilan, 2010
;
Wang, Fewer, & Sivonen, 2011
), including vitamin-rich food and thera-
peutics (
Williams, 2009
), isotope-labelled molecules and bioplastics (
Abed,
Dobretsov, & Sudesh, 2009
); and for the bioremediation of polluted soil
and waters (
De Philippis, Colica, & Micheletti, 2011
). All these potentials
benefit from the capacity of cyanobacteria to grow in a variety of locations.
In turn, this enables industrial productions to be performed near the sites of
use, thereby reducing transportation costs.
1.2. Size, Organization and Ploidy of Cyanobacterial
Genomes
The two first articles reporting the sequence of an entire bacterial genome
(
Haemophilus influenzae
, 1,830,137 bp;
Mycoplasma genitalium
, 580,070 bp)
appeared in 1995 (
Fleischmann et al., 1995
;
Fraser et al., 1995
). Very
shortly thereafter, the sequence of the 3,573,470-bp chromosome (not of
the plasmids at that time) of the widely used unicellular cyanobacterium
Synechocystis
PCC 6803 was published (
Kaneko et al., 1996
), and modern
comparative genomics was born. The number of fully sequenced genomes
grew rapidly. Currently, about 50 complete and 20 draft sequences of cya-
nobacterial genomes are accessible in public data bases such as Cyanobase
(
http://genome.kazusa.or.jp/cyanobase/
), DOE joint genome institute
(
http://genome.jgi.doe.gov/genome-projects
), and Microbial Genome
Database for Comparative Analysis (
http://mbgd.genome.ad.jp/
), and an
ever increasing number of cyanobacterial genes are being sequenced in
the frame of metagenomic analyses (
Hess, 2011
;
Scanlan et al., 2009
;
Wang
et al., 2011
). These data allow to determining which genes are present in
any particular genome and which ones are absent. In turn, these informa-
tion are crucial for genome-based reconstruction of an organism's metab-
olism as recently done for the model cyanobacterium
Synechocystis
PCC
6803 (
Yoshikawa et al., 2011
), and reconstructions of genome evolution
