Biology Reference
In-Depth Information
Figure 7: Members of Nostocales.
Trichomes of
Arthrospira maxima
(A),
Microcoleus lacustris
(B) and
Porphyrosiphon
sp.
(C). Magnifi cation bar in picture (B) 10 µm and picture (C) 5 µm. Pictures (A) and (B) courtesy Mark T. Aubel, GreenWater
Laboratories/CyanoLab, 205, Zeagler Drive, Suite 302, Palatka, Florida 32177, USA. (http://www.greenwaterlab.com/photo_
algal.htm). Picture (C) courtesy G. L. Tiwari, Department of Botany, University of Allahabad, Allahabad-211002, India.
numerous clusters identifi ed on the basis of 16S rRNA sequencing are more or less congruent with
traditional taxonomic assignments. In this connection mention may be made of Oscillatorian genera
Planktothrix
,
Tychonema
,
Microcoleus
,
Trichodesmium
,
Arthrospira
and
Spirulina
. These are distinguishable
on the basis of morphological features as well as their 16S rRNA sequence divergence is near 95% as
suggested for distinguishing bacterial genera (Wayne
et al
., 1987; Stackebrandt and Goebel, 1994).
Similarly, in heterocystous genera
Cylindrospermum
,
Cylindrospermopsis
and
Anabaenopsis
are distinct
morphologically and on molecular phylogeny.
Based on the recommendations of the subcommittee on Phototrophic Bacteria of the International
Committee on Systematic Bacteriology (ICSB) of the International Association of Microbiological
Societies (IAMS), the cyanobacteria have been included under the Ist Division followed by the bacteria
in the IInd division in the eigth edition of Bergey's Manual of Determinative Bacteriology (Buchanan
and Gibbons, 1974). However, looking into the advances made in the physiology, biochemistry
