Biology Reference
In-Depth Information
unbranched and branched representatives, respectively. The following is the classifi cation scheme
presented by Rippka
et al
. (1979) for cyanobacteria.
Section I (Unicellular):
This section consists of unicellular cyanobacteria that reproduce by binary
fi ssion or by budding and separated into three groups on the basis of baeocyte (a new term coined
to represent the erstwhile endospores or exospores) formation. The fi rst group comprises of
Synechococcus
Nageli 1849 (thylakoids present; sheath absent);
Gloeothece
Nageli 1849 (thylakoids
present; sheath present) and
Gloeobacter
Rippka, Waterbury & Cohen-Bazire 1974 (thylakoids absent;
sheath absent) that form baeocytes by binary transverse division.
The second group comprises
unicellular members that produce baeocytes in two or three successive planes and represented
by
Synechocystis
Sauvageau 1892 (thylakoids present; sheath absent) and
Gloeocapsa
Kützing 1843
(thylakoids present; sheath present). The third group is represented by
Chamaesiphon
Braun & Grunow
1895 emend Geitler 1925 that reproduces by budding from one pole of the ovoidal cell.
Section II (Unicellular):
This section is divided into three groups. The fi rst group is represented by
members that are unicellular and reproduce by the formation of baeocytes by multiple fi ssion and
the baeocytes may be motile or immotile. Examples are
Dermocarpa
Crouan & Crouan 1858 (motile
baeocytes) and
Xenococcus
Thuret 1880 (immotile baeocytes). The members of the second group
reproduce both by binary fi ssion and multiple fi ssion and represented by
Dermocarpella
Lemmermann
1907;
Myxosarcina
Printz 1921;
Chroococcidiopsis
Geitler 1933.
Pleurocapsa
-group
with binary fi ssion
yields irregular cellular aggregates and forms pseudofi lamentous structures with the formation of
motile baeocytes by multiple fi ssion.
Section III (Filamentous):
Filamentous non-heterocystous cyanobacteria that divide in only one
plane with helical (
Spirulina
Turpin 1827) or straight trichomes (
Oscillatoria
Vaucher 1803) are included
here. The other non-heterocystous cyanobacteria (
Lyngbya
,
Phormidium
and
Plectonema
) have been
merged into LPP group A:
Pseudoanabaena
Lauterborn 1915 and LPP group B.
Section IV (Filamentous):
This
section
consists of
fi lamentous cyanobacteria that form heterocysts
and divide in only one plane. On the basis of hormogone formation, cell size and shape two groups
are recognized. The members of the fi rst group
reproduce by random trichome breakage to form
hormogones that are indistinguishable in cell size and shape from main fi laments and some form
akinetes.
Anabaena
Bory de St. Vincent 1822,
Nodularia
Mertens 1822 and
Cylindrospermum
Kützing
1843 are the representatives. The members of the second group form hormogones with rapid gliding
motility and possess smaller cells with gas vacuoles.
Nostoc
Vaucher 1803,
Scytonema
Agardh 1824
and
Calothrix
Agardh 1824 are the genera recognized.
Section V (Filamentous):
These are represented by heterocystous, branched forms that divide in
more than one plane, form hormogones and some differentiate akinetes.
Chlorogloeopsis
Mitra &
Pandey 1966 and
Fischerella
Gomont 1895 are the representatives.
The scheme of Rippka
et al.
(1979) was adopted and modifi ed in Bergey's Manual of Systematic
Bacteriology (Boone and Castenholz, 2001). The cyanobacteria constitute a monophyletic group
within Eubacteria and are closely related to purple bacteria and gram-positive bacteria. At present,
the phylum cyanobacteria includes two groups of oxygenic photosynthetic bacteria i.e. chlorophyll-
b/a
containing Prochlorales (Prochlorophyta), and cyanobacteria (Castenholz, 2001). In this Manual fi ve
Subsections (“Orders”) have been recognized. Subsection I consists of unicellular or non-fi lamentous
aggregates of cells (or in other words colonial forms) that reproduce by binary fi ssion in one, two or
three planes, symmetric or asymmetric or by budding (corresponding to the Order Chroococcales
