The Family Ectothiorhodospiraceae
- PDF / 504,486 Bytes
- 13 Pages / 539 x 751 pts Page_size
- 58 Downloads / 169 Views
CHAPTER 3.3.32 ehT
y l imaF
eaecar i psodohro i htot cE
The Family Ectothiorhodospiraceae JOHANNES F. IMHOFF
Phylogeny
Taxonomy
Separate phylogenetic lineages are represented by the purple sulfur bacteria belonging to the γProteobacteria (Chromatiaceae and Ectothiorhodospiraceae) and by the purple nonsulfur bacteria, belonging to the α-Proteobacteria and β-Proteobacteria. Ectothiorhodospiraceae represent halophilic and alkaliphilic purple sulfur bacteria that form a separate lineage of phylogenetic descent related to the Chromatiaceae, as was first demonstrated by analysis of rRNA oligonucleotide catalogues (Stackebrandt et al., 1984). In a phylogenetic tree based on 16S rDNA sequences, both families form distinct groups within the γ-Proteobacteria (Imhoff and Süling, 1996). The salt requirement not only is a characteristic property of all Ectothiorhodospiraceae, but also distinguishes moderately and extremely halophilic Halorhodospira species from slightly halophilic Ectothiorhodospira and Thiorhodospira species. Two clearly distinct phylogenetic lineages within the Ectothiorhodospiraceae separate the slightly halophilic and marine species from the moderately to extremely halophilic species (see Fig. 1). Correlation between salt relations and phylogenetic position of the purple sulfur bacteria point out the phylogenetic and taxonomic importance of salt requirement and salt dependence, which also distinguishes major phylogenetic groups of the Chromatiaceae (Imhoff et al., 1998b) and genera of the purple nonsulfur bacteria such as Rhodobacter and Rhodovulum (Hiraishi and Ueda, 1994) and others (Imhoff et al., 1998a). At present, Arhodomonas aquaeolei is the only nonphototrophic, purely chemotrophic representative in this lineage, which is closely related to Halorhodospira species (Adkins et al., 1993; Imhoff and Süling, 1996).
Ectothiorhodospiraceae The taxonomic position of the Ectothiorhodospiraceae has been disputed since their discovery by Pelsh, 1936. He distinguished phototrophic purple sulfur bacteria that deposit elemental sulfur globules outside the cells, which he called “Ectothiorhodaceae,” from those with elemental sulfur inside their cells, which he called “Endothiorhodaceae” (Pelsh, 1937). Pelsh’s isolates were lost, but Ectothiorhodospira mobilis was reisolated (Trüper, 1968), and the genus Ectothiorhodospira included into the Chromatiaceae (Pfennig and Trüper, 1971) because of the ability to perform an oxidative dissimilatory sulfur metabolism similar to other phototrophic purple sulfur bacteria. Later, a clear differentiation of Ectothiorhodospira species from Chromatiaceae was demonstrated by oligonucleotide patterns of 16S rRNA molecules (Stackebrandt et al., 1984), substantiated by 16S rDNA sequence analyses (Imhoff and Süling, 1996), and a separation of the Ectothiorhodospiraceae as a family distinct from the Chromatiaceae was proposed (Imhoff, 1984a). The complete sequence analysis of the 16S rDNA from a large number of strains including all available type strains of Ectothiorhodospira and
Data Loading...
