Biology Reference
In-Depth Information
Komárek 1964/112 and
L
.
boryanum
PCC 73110, Nelissen
et al
. (1996) also described the presence of
Oscillatoria amphigranulata
CCCNZ-Concert-Oa-1,
Leptolyngbya minutum
D5 and the marine strains
L. ectocarpi
PCC 7375,
L
.
ectocarpi
N 182 and
L
.
ectocarpi
CCAP 1462/5 in this cluster but poorly
supported by bootstrap values. However,
L
.
foveolarum
Komárek 1964/112 and
L
.
boryanum
PCC
73110 showed 99.5% 16S rDNA sequence similarity with 100% bootstrap support. On the basis
of phylogenetic analysis, Nelissen
et al
. (1996) are of the opinion that
O
.
amphigranulata
CCCNZ-
Concert-Oa-1 should be assigned to the genus
Leptolyngbya
despite the fact that
O
.
amphigranulata
Van Goor was assigned to the genus
Limnothrix
by Anagnostidis and Komárek (1988). Castenholz
(1992) suggested that the morphological descriptions of
O
.
amphigranulata
CCCNZ-Concert-Oa-1
and
O
.
amphigranulata
Van Goor are different and that the latter should be assigned to a new genus
and species altogether. The 16S rRNA gene sequences of
Phormidium
M-99 and
Oscillatoria
M-117
are shown to be identical to those of this lineage but Ishida
et al
. (1997) have not documented the
morphological identifi cation for these strains.
A polyphasic taxonomic approach has been undertaken to resolve 75 strains of Oscillatorioid
cyanobacteria by taking into consideration morphological characters, growth temperature, salinity
tolerance, complementary chromatic adaptation (CCA), DNA base composition and 16S rDNA
analysis. Six groups have been identifi ed on the basis of 16S rDNA sequencing, all of which are
clearly separated from the type species
Oscillatoria princeps
Gomont NIVA CYA 150. That is why
Suda
et al
. (2002) recommended that these strains should be classifi ed into separate genera other
than
Oscillatoria
. Groups I-III are closely related to each other and Groups IV-VI are distinct from
one another and from Groups I-III. Group I is subdivided into strains producing PC (Group I-pc)
and PE in addition to PC (Group I-pe). The mol% G+C content of Groups I and II is 39.5 ± 0.4 and
39.5 ± 0.2 respectively whereas Group III showed a mol% G+C of 40.0 ± 0.2. A slightly higher mol%
G+C of 44.0 ± 0.4 and 44.0 ± 0.6 is found in Groups IV and V, respectively. The similarity of 1361 bp
region of 16S rDNA is in the range of 95.4-96.8% for Groups I-III and fatty acid composition of these
strains is similar. Strains of Group IV exhibited a similarity of 89.7% and the fatty acid composition
of this group is different. These results are supported by DNA:DNA hybridization studies.. Group
I consisted of 58 strains with a RB value of 99.2%. Groups II and III were represented by 5 and 4
strains with RB values at 98.4% and 99.8%, respectively. Group IV was represented by 6 strains
and these within each other exhibited an RB value of 99.1%. Groups V and VI are represented by
one strain each with RB values of 91.9% and 86.4%, respectively with other groups. On the basis
of overall assessment, strains of group I-pc have been treated as
Planktothrix
agardhii
and those of
group I-pe as
Planktothrix
rubescens
. They also considered it appropriate to treat
O
.
mougeotii
Kützing
ex Forti as a synonym of
P. rubescens
(
O
.
rubescens
). Amended or new taxonomic descriptions (for
the subgroups and groups) for
P. agardhii
(type strain NIES 204
T
),
P. rubescens
(type strain CCAP
1459/22
T
),
Planktothrix pseudoagardhii
sp. nov. (type strain T 1-8-4
T
),
Planktothrix
mougeotii
(type
strain TR1-5
T
),
Planktothricoides raciborskii
gen nov.comb. nov. (type strain NIES 207
T
),
Tychonema
bourrellyi
(type strain CCAP 1459/11B
T
) and
Limnothrix
redekei
(type strain NIVA CYA 277/1
T
) have
been presented.
The studies of Thacker and Paul (2004) on morphological, chemical and genetic diversity of
Lyngbya
spp. and
Symploca
spp. revealed that 16S rDNA sequence analysis though strongly supported
monophyly of
Lyngbya
and
Symploca
as well as monophyly of
L
.
bouillonii
and
L
.
majuscula
but it
does not explain the chemical variability among the
Lyngbya
species.
(iv)
Pseudoanabaena
cluster (VI lineage according to Wilmotte and Herdman, 2001):
In most of
the strains of
Pseudoanabaena
the trichomes are less than 4 µm width with cells longer than broad
and possess constricted cross walls (Castenholz, 2001; Komárek, 2003). Some of the strains exhibit