TY - JOUR
T1 - The phylogeny of unicellular, extremely halotolerant cyanobacteria
AU - Garcia-Pichel, Ferran
AU - Nübel, Ulrich
AU - Muyzer, Gerard
N1 - Funding Information:
Acknowledgements We would like to thank Exportadora de Sal, S. A. de C. V. (Mexico) for allowing us to conduct research on their premises, P. M. Sánchez-Castillo and M. Hernández-Mariné for field guidance in Spain, A. Oren for Israeli samples, Y. Cohen for the gift of strain SYN CI P22, and B. Nelissen for unpublished sequence data of strain PCC 7403. R. W. Castenholz and two anonymous reviewers improved this manuscript substantially through their comments and suggestions. This work was supported by funds from the Deutsche Forschungsgemeinschaft (Schwer-punktprogramm: Struktur und Funktionsanalyse mikrobieller Lebensgemeinschaften), the EC program “Biodiversity: Applied and Systematic Investigations of Cyanobacteria” (BASIC; contract no. BIO4-CT96-0256), and by the Max-Planck-Gesellschaft.
PY - 1998
Y1 - 1998
N2 - We examined the morphology, physiology, and 16S rRNA gene sequences of three culture collection strains and of ten novel isolates of unicellular cyanobacteria from hypersaline environments. The strains were morphologically diverse, with average cell widths ranging from 2.8 to 10.3 μm. There were single-celled, colonial, and baeocyte-forming strains. However, morphological traits were markedly variable with culture conditions. In contrast, all strains displayed extreme halotolerance (growing close to optimally at above 12% salinity); all were obligately marine, euryhaline, and moderately thermophilic; and all shared a suite of chemotaxonomic markers including phycobitins, carotenoids, and mycosporine-like amino acids. 16S rRNA gene sequence analysis indicated that the strains were related to each other. Sequence similarity analysis placed the strains in a monophyletic cluster (which we named the Halothece cluster) apart from all cultured or uncultured, not extremely halotolerant cyanobacteria whose 16S rRNA gene sequences are available in public nucleotide sequence databases. This represents the first case in which a phylogenetically coherent group of cyanobacteria can be defined on the basis of physiology. The Halothece cluster contained two subclusters that may be divergent at the generic level, one encompassing 12 strains (spanning 5% 16S rRNA gene sequence divergence and named the Euhalothece subcluster), and a single deep-branching isolate. Phenotypic characterization of the isolates, including morphological, physiological, and chemotaxonomic traits, did not distinguish these subclusters and only weakly suggested the existence of two separate clades, one encompassing strains of small cell size (cell width < 5 m) and another one encompassing strains of larger cell size.
AB - We examined the morphology, physiology, and 16S rRNA gene sequences of three culture collection strains and of ten novel isolates of unicellular cyanobacteria from hypersaline environments. The strains were morphologically diverse, with average cell widths ranging from 2.8 to 10.3 μm. There were single-celled, colonial, and baeocyte-forming strains. However, morphological traits were markedly variable with culture conditions. In contrast, all strains displayed extreme halotolerance (growing close to optimally at above 12% salinity); all were obligately marine, euryhaline, and moderately thermophilic; and all shared a suite of chemotaxonomic markers including phycobitins, carotenoids, and mycosporine-like amino acids. 16S rRNA gene sequence analysis indicated that the strains were related to each other. Sequence similarity analysis placed the strains in a monophyletic cluster (which we named the Halothece cluster) apart from all cultured or uncultured, not extremely halotolerant cyanobacteria whose 16S rRNA gene sequences are available in public nucleotide sequence databases. This represents the first case in which a phylogenetically coherent group of cyanobacteria can be defined on the basis of physiology. The Halothece cluster contained two subclusters that may be divergent at the generic level, one encompassing 12 strains (spanning 5% 16S rRNA gene sequence divergence and named the Euhalothece subcluster), and a single deep-branching isolate. Phenotypic characterization of the isolates, including morphological, physiological, and chemotaxonomic traits, did not distinguish these subclusters and only weakly suggested the existence of two separate clades, one encompassing strains of small cell size (cell width < 5 m) and another one encompassing strains of larger cell size.
KW - Cyanobacteria
KW - Halophiles
KW - Halotolerance
KW - Hypersaline environments
KW - Microbial mats
KW - Phylogeny
KW - Taxonomy
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U2 - 10.1007/s002030050599
DO - 10.1007/s002030050599
M3 - Article
C2 - 9575232
AN - SCOPUS:0031810473
SN - 0302-8933
VL - 169
SP - 469
EP - 482
JO - Archives of Microbiology
JF - Archives of Microbiology
IS - 6
ER -