Biology Reference
In-Depth Information
PCC 7414,
Fischerella
sp. 1711 and
Fischerella
sp. SAG 2027)
Hapalosiphon
Näg. in Kütz. ex Born.et
Flah.1886 (
Hapalosiphon
sp. 804-1),
Mastigocladopsis
Iyeng. et Desik. 1946 (
Mastigocladopsis repens
MORA),
Nostochopsis
Wood. ex Born. et Flah. 1886 (
Nostochopsis
sp. 89-45),
Stigonema
Ag. ex Born.
et Flah. 1886 (
Stigonema ocellatum
SAG 48.90),
Symphyonema
Jao 1944 (
Symphyonema
sp. 1269.1 and
Symphyonema
sp. 1517),
Symphyonemopsis
Tiwari et Mitra 1969 (
Symphyonemopsis
sp. VAPOR1)
and
Westiellopsis
Janet 1941 (
Westiellopsis prolifi ca
SAG 16.93,
Westiellopsis
SAG 23.96,
Westiellopsis
sp. 1590-1,
Westiellopsis
sp. 1590-2,
Westiellopsis
sp. 89-785/4 and
Westiellopsis
sp. 985-1) have been
selected that differed from one another in the type of branching (Y vs T-branching) and the position
of heterocysts (intercalary, lateral-sessile and lateral-pedicellate). A phylogenetic study of these
strains based on 16S rRNA gene sequencing following NJ method revealed four clusters (Clusters 1,
2, 3 and 5). Clusters 2 and 3 are always basal to Cluster 1 and all these exhibit T-branching whereas
Cluster 5 is composed of Y-branching types such as
Symphyonema
and
Symphyonemopsis
. These results
do not correlate with the traditional as well as bacteriological classifi cations. Other heterocystous
unbranched members (
Nodularia,
Anabaena
,
Aphanizomenon
,
Nostoc
,
Cylindrospermopsis
) are present
in Cluster 4 whereas
Scytonema hofmanni
PCC 7110 and
Scytonema
sp. are present in Cluster 6.
Rajaniemi
et al.
(2005) investigated the molecular phylogeny of heterocystous cyanobacteria and
included
Anabaena
,
Aphanizomenon
,
Trichormus
and
Nostoc
in their study. Most of the 51 strains selected
were representatives of the planktic
Anabaena
and
Aphanizomenon
. The former was represented
by 10 species (
A
.
crassa
(Lemm.) Kom.-Legn. et CronB.,
A. circinalis
Rabenh. ex Born. et Flah.,
A
.
planctonica
Brunnth.,
A
.
mucosa
Kom.-Legn. et Eloranta,
A
.
spiroides
Kleb.,
A
.
smithii
(Kom.) M.
Watan.,
A
.
sigmoidea
Nyg.,
A
.
fl os-aquae
[Lyngb.] Bre´b. ex Born. et Flah.,
A
.
cf. circinalis
var.
macrospora
and
A
.
lemmermannii
Richt) while the latter by three species [
Aph. fl os-aquae
Ralfs ex Born. et Flah.,
Aph
.
gracile
(Lemm.) Lemm. and
Aph
.
issatschenkoi
(Usaˇ) Proˇk.-Lavr.,] as identifi ed according to
traditional morphological criteria (Geitler, 1932; Desikachary, 1959; Komárek and Anagnostidis, 1989).
It is pertinent to mention here that the genus
Trichormus
was created by Komárek and Anagnostidis
(1989) by transferring three species of
Anabaena
(
A
.
variabilis
Born. et Flah,
A
.
azollae
Strasb. and
A
.
doliolum
Bharadw.) on the basis of akinete development. In addition, nine benthic species of
Anabaena
and three of
Trichormus
(
T
.
variabilis
(Born. et Flah.) Kom. et Anag.,
T
.
azollae
(Strasb.)
Kom. et Anag.,
T
.
doliolum
(Bharadw.) Kom. et Anag) and
Nostoc
sp. have been included based
on traditional morphological criteria. On the basis of 16S rRNA,
rpoB
and
rbcLX
gene sequence
phylogenetic analyses, Rajaniemi
et al
. (2005) identifi ed six clusters. Cluster I is characteristic in
consisting of
Anabaena
and
Aphanizomenon
strains as well as fi ve benthic
Anabaena
strains (BECID22,
BECID32, XP6B, Itu34S7 and 277) that lack gas vesicles got intermixed with planktic
Anabaena
and
Aphanizomenon
in Cluster I with high bootstrap support. These results thus do not support the
separation of planktic and benthic
Anabaena
/
Aphanizomenon
strains as has been done earlier by
Iteman
et al
. (2002) who found a subcluster of planktic heterocystous cyanobacteria with the exception
of
Cylindrospermopsis
. Cluster I is further subdivided into nine subclusters (i.e. A-I). On the basis of
cutoff points suggested for bacterial species and genus, 97.5% and 95% 16S rRNA sequence identity,
respectively, these can be divided into more than three (or up to nine) species. NJ method based on
16S rRNA gene sequences showed clustering of
Anabaena
,
Aphanizomenon
,
Trichormus
and
Nostoc
with bootstrap support of over 65% for NJ, MP and ML methods of analyses. Studies on principal
component analysis of morphological characters revealed that shape and size of akinetes afforded an
important parameter for differentiating
Anabaena
,
Aphanizomenon
,
Trichormus
and
Nostoc
strains. The
species of
Trichormus
reognised by Komárek and Anagnostidis (1989) did not form a monophyletic
cluster. Accordingly, the three species of
Anabaena
transferred by Komárek and Anagnostidis (1989)
to designate
Trichormus
probably are distinct species. It is interesting to note that benthic
Anabaena
/
