Biology Reference
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BBCUSP 352 and G . unigranulatum BBCUSP 94) have been found to be distinct from all others
despite their morphological similarity. These two strains could be assigned to a different species
of Geitlerinema . However, on the basis of morphological features, cell ultrastructure and PC-IGS
sequences, G . amphibium and G . unigranulatum are indistinguishable and so can be merged into
a single species (Figs. 18, 19 and 20). Phylogenetic trees constructed by MP, NJ, ML and Bayesian
analyses revealed similar pattern in the clades as well as the clades remained the same by the rooted
and unrooted trees.
Figure 18: Electron micrographs of Geitlerinema amphibium longitudinal and cross sections of strains BCCUSP91 (A and B)
and BCCUSP85 (C and D), respectively. 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.
PCR and DGGE analysis in cyanobacteria
Any gene sequence that shows considerable sequence heterogeneity can be chosen as a molecular
marker for assessing the microbial diversity through this method. DGGE analysis of 16S rRNA gene
segment of cyanobacterial populations has been done (Nübel et al ., 1997; Garcia-Pichel, 2000; Abed
and Garcia-Pichel, 2001). Due to the fact that 16S rRNA gene falls short of resolving differences
between closely related organisms, a number of workers consider 16S rRNA-23S rRNA ITS region to
be very suitable for high resolution analysis because of greater degree of sequence heterogeneity and
the availability of published rRNA-ITS sequences. DGGE has been used for analysis of Synechococcus
(Becker et al ., 2002) and Aphanizomenon (Laamanen et al ., 2002) strains on the basis of 16S rRNA-23S
rRNA ITS sequences. Amplifi cation of ITSa region gave rise to one sharp band occupying an unique
position in the gel in all the cyanobacteria studied. However, only Aph. gracile yielded two bands.
The amplifi cation products of ITSb and ITSc regions that were longer when subjected to DGGE
gave rise to one (in case of Synechococcus , Synechocystis , Lyngbya , Pseudoanabaena , Trichodesmium and
Prochlorothrix ), two (in case of Leptolyngbya ) and two to four bands (in case of most of the strains
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