Biology Reference
In-Depth Information
Table 5:
Distribution of genes to the functional categories in four cyanobacterial genomes.
Functional Category
Synechocystis
sp.
strain PCC6803
a
G
.
violaceus
PCC7421
b
T
.
elongatus
BP-1
c
Anabaena
sp. strain
PCC7120
d
Amino acid biosynthesis
97
106
99
111
Biosynthesis of co-factors, Prosthetic groups
and carriers
124
141
120
152
Cell envelope
67
61
56
80
Cellular processes
78
86
78
94
Central intermediary metabolism
31
30
23
70
Energy metabolism
93
102
72
98
Fatty acid, phospholipid and sterol
metabolism
39
53
29
41
Photosynthesis and respiration
141
158
124
156
Purines, Pyrimidines, nucleosides,
nucleotides
41
46
41
57
Regulatory functions 146 195 87 339
DNA replication, recombination, repair 60 68 62 93
Transcription 30 44 29 38
Translation 168 193 151 189
Transport and binding proteins 196 226 153 294
Other categories 312 327 266 584
Total number of genes of known function 2756 1836 1390 2396
Total number of genes 3264 4430 2475 5368
a (after Kaneko
et al
., 1996); b (after Nakamura
et al
., 2003); c (after Nakamura
et al
., 2002); d (after Kaneko
et al
., 2001).
a
de novo
pathway concerning the conversion of aspartate to NaMN is governed by a group of three
genes (
nadB
,
nadA
and
nadC
) scattered all over the genomes. The presence of three other genes (
nadD
,
nadE
and
nadK
) that mediate conversion of NaMN to NADP are seen in all the genomes with the
exception of
nadD
and
nadE
orthologues form a chromosomal cluster in all cyanobacteria except in
the model organism where these occur in distal chromosomal loci.
2) Cell envelope
:
Rocap
et al
. (2003) identifi ed a 41.8 kb cluster of surface polysaccharide genes in a
lower G+C (42%) region than the genome as a whole suggesting that it might have been acquired
by
P. marinus
MIT9313 through LGT. In contrast,
P. marinus
MED4 has acquired a considerably large
cluster (74.5 kb) consisting of 67 potential surface polysaccharide genes.
Synechococcus
sp. strain
WH8102 possesses genes
SwmA
and
SwmB
for swimming motility. These genes are located in a
low G+C region of the genome and of these
SwmB
encodes a large protein with 10,791 amino acids.
Homologues of
pilB
, -
C
, -
D
, -
Q
and -
T
that govern twitching motility are represented in the genome of
Synechococcus
sp. strain WH8102 but orthologues of these genes are only represented in the genome
of
P. marinus
MIT9313 but not in MED4 (Palenik
et al
., 2003). Palenik
et al
. (2006) compared cell
envelope of
Synechococcus
sp. strain CC9311 with that of
Synechococcus
sp. strain WH8102. There are
a number of differences in the synthesis of LPS as
Synechococcus
sp. strain CC9311 lacks genes that
encode KDO (a molecule necessary for biosynthesis of typical LPS) and for rhamnose biosynthesis
(this sugar also is a potential component of LPS). It means that the type of LPS synthesized by
Synechococcus
sp. strain CC9311 is quite different in its properties thus affecting the sensitivity of
this organism to certain phages. The presence of genes for pilin and pilin biosynthesis is indicative
of pili-mediated twitching motility or DNA uptake in
Synechococcus
sp. strain CC9311. However,
this strain lacks the two major surface proteins,
SwmA
and
SwmB
involved in swimming motility
of
Synechococcus
sp. strain WH8102. A comparison of cell envelope related genes in the genomes
