Biology Reference
In-Depth Information
Figure 20:
Electron micrographs of
G
.
unigranulatum
BCCUSP47 strain longitudinal (A) and cross sections (B). Scale bar 500
nm. Photographs courtesy M. D. C. Bittencourt-Olievera, Department of Biological Sciences, Luiz de Queiroz College of
Agriculture, University of S˜o Paulo, Piracicaba 13418-900, SP, Brazil.
organisms (Lovell
et al
., 2001) have been employed. Berrendero
et al
. (2008) compared phylogenetic
relartionships based on 16S rRNA gene sequences with the variability in PC operon and the
intervening spacer sequence (
cpcBA-IGS
) between strains of
Rivularia
and
Calothrix
by temperature-
dependent DGGE. The high variability of the
PC-IGS
among the genotypes was not consistent with
the morphologies observed. However, the phylogenetic relationship drawn in case of
cpcBA-IGS
is
largely consistent with 16S rRNA gene sequences.
Phylogenetic analysis based on the sequences of the nitrogen-fi xing gene
nifD
from a number
of representatives of subsection IV and subsection V refl ected the monophyly of the heterocystous
cyanobacteria. Neither of these subsections is monophyletic because of intermixing of the strains
with two sister clades. Clade I is composed of two smaller branches Clade 1a and Clade 1b.
Clade 1a consisted of representatives of
Calothrix
(IV.II; strain PCC 7102),
Scytonema
(IV.I; PCC
7814 and PCC 7110),
Fischerella
(V; strains PCC 7603, PCC 7414, PCC 1903) and
Chlorogloeopsis
(V;
strain PCC 6718) and Clade 1b was represented by
Nostoc
(IV.I; strains PCC 7120, PCC 6720, PCC
7423),
Cylindrospermum
(IV.I; PCC 7604) and
Chlorogloeopsis
(V; PCC 6912). Clade 2 is composed of
strains of
Calothrix
,
Nostoc
,
Anabaena
(IV.I),
Nodularia
(IV.I),
Cylindrospermum
and
Tolypothrix
(IV.II).
Intermingling of strains of
Calothrix
(PCC 7507) with those of
Nostoc commune
UTEX 584 and sister
Anabaena
strains (PCC 7122, PCC 7108 and ATCC 33047) has been noted in Clade 2. The MP and NJ
trees were virtually identical to ML tree (Henson
et al
., 2004).
