Biology Reference
In-Depth Information
CCA by regulating the levels of PC and PE according to the available spectrum of light. The presence
of gliding motion and the ability to fi x atmospheric nitrogen are the other traits exhibited by some
other strains of this genus. Due to the closer resemblances of
Pseudoanabaena
spp. with those of
Limnothrix
as well as their occurrence together makes their identifi cation slightly diffi cult. Acinas
et al
. (2009) conducted a phylogenetic study of 28
Pseudoanabaena
strains from Baltic Sea (BS) and
the Albufera de Valencia (AV) on the basis of sequencing of 16S rRNA and 23S rRNA genes, their
ITS1
region, the
cpcBA
operon, the
IGS
between
cpcA
and
cpcB
and the
nifH
. These studies revealed
the existence of specifi c clusters for strains from BS and AV and a third cluster contained a mixture
of strains from both the geographical regions that exhibited CCA. Although the analyses from 16S
rRNA and 23S rRNA genes are consistent but the analyses from other loci indicated extensive genetic
recombination between strains. 16S rDNA analysis revealed clustering of certain
Pseudoanabaena
with
strains of
Limnothrix
including
L
.
redekei
. These observations are consistent with the earlier fi ndings of
Wilmotte and Herdman (2001). This cluster is commonly called as
Pseudoanabaena
/
Limnothrix
group.
Several environmental sequences as well as other isolates including the type strain
Pseudoanabaena
PCC 7408 and several strains of
Limnothrix
from Lake Loosdrecht along with
Limnothrix redekei
CCAP
1443/1 and
Limnothrix redekei
CCAP 227/1 are members of this lineage.
v)
Trichodesmium
-
Oscillatoria
PCC 7515 lineage (XII lineage according to Wilmotte and Herdman,
2001):
So far fi ve species of
Trichodesmium
have been described (Wille, 1904; Sournia, 1968) and these
have been further confi rmed by both morphological as well as ultrastructural features. These fi ve
species of
Trichodesmium
are,
T.
thiebautii
,
T. erythaeum
,
T. tenue
,
T. contortum
, and
T. hildebrandtii
(Janson, 1995). There is very low genetic diversity amongst these strains as revealed by molecular
approaches of sequence analysis of
nifH
,
hetR
, and 16S rRNA (Carpenter, 1983; Zehr
et al
., 1990;
Ben-Porath
et al
., 1993). Wilmotte
et al
. (1994) showed that
Trichodesmium
sp. strain NIBB 1067 is closely
related to
Oscillatoria sancta
PCC 7515 showing 94.9% 16S rRNA gene sequence similarity. Genes
encoding tRNA
Ile
and tRNA
Ala
are present in the 16S rRNA-23S rRNA ITS region of
Trichodesmium
.
On the basis of 16S rDNA and
hetR
sequences, Janson
et al
. (1999) were able to resolve three
clades
in
Trichdesmium
containing (i)
T. thiebautii
and
T. hildebrandtii
, (ii)
T. contortum
and
T. tenue
, and (iii)
T. erythraeum
. However, the
hetR
sequenceing provided a better
resolution between the species
T.
erythraeum
and
T. thiebautii
than analysis of the 16S rDNA region gave.
Orcutt
et al
. (2002) investigated
the genetic diversity of
Trichodesmium
spp. by using three independent techniques that provide high
resolution. A PCR-based DNA fi ngerprinting method using base pair extended short oligonucleotide
primers for HIP1 was used to distinguish
Trichodesmium
spp. This technique was used to distinguish
a number of strains of cyanobacteria (Robinson
et al
., 1995; Smith
et al
., 1998). Further, DGGE
analysis of a fragment of
hetR
gene and the sequencing of 16S rRNA-23S rRNA ITS region were also
conducted to reveal the genetic diversity in this genus. Natural populations of
Trichodesmium
spp.
(from Bermuda in the Sargasso Sea and North Australia in the Arafura and Coral Seas) and some
culture isolates (from Sargasso Sea and the Indaian Ocean) were subjected to diversity studies by
employing the above three methods. Although a remarkable similarity existed in between cultures
of
T
.
thiebautii
,
T
.
hildebrandtii
,
T
.
tenue
and
Katagnymene
spiralis
, low genetic diversity was revealed in
the strains from the two hemispheres. Two major clades are recognized and largest genetic variation
was found in between the strains of
T
.
erythraeum
(Orcutt
et al
., 2002).
vi)
Geitlerinema
lineage (XIV cluster according to Wilmotte and Herdman, 2001):
Bittencourt-
Oliveira
et al
. (2009) conducted a phylogenetic study of ten strains of
Geitlerinema
[six of
Geitlerinema
amphibium
(C. Agardh ex Gomont) Anag. and four of
Geltlerinema unigranulatum
(Rama N. Singh)
Komárek et M.T.P. Azevedo] on the basis of PC-IGS sequencing. Two strains (
G
.
unigranulatum
