Transfer of Rhodopseudomonas Acidophila to the New Genus
International Journal of Systematic and Evolutionary Microbiology (2001), 51, 1863–1866 Printed in Great Britain
Transfer of Rhodopseudomonas acidophila to NOTE the new genus Rhodoblastus as Rhodoblastus acidophilus gen. nov., comb. nov.
Marine Mikrobiologie, Johannes F. Imhoff Institut fu$ r Meereskunde, Du$ sternbrooker Weg 20, D-24105 Kiel, Germany Tel: j49 431 600 4450. Fax: j49 431 565 876. e-mail: jimhoff!ifm.uni-kiel.de
Rhodopseudomonas acidophila has unique properties among the phototrophic α-Proteobacteria and is quite distinct from the type species of Rhodopseudomonas, Rhodopseudomonas palustris. Therefore, the transfer of Rhodopseudomonas acidophila to Rhodoblastus acidophilus gen. nov., comb. nov., is proposed. This proposal is in accordance with other taxonomic reclassifications proposed previously and fully reflects the phylogenetic distance from Rhodopseudomonas palustris.
Keywords: phototrophic purple bacteria, Rhodopseudomonas, new combination, Rhodoblastus
The great diversity of purple non-sulfur bacteria is coloured and bacteriochlorophyll b-containing species reflected not only in their morphological properties were transferred to the genus Blastochloris (Hiraishi, such as cell form, type of flagellation, internal mem- 1997), Rhodopseudomonas marina was transferred to brane structures and their physiological functions. It is Rhodobium marinum (Hiraishi et al., 1995) and Rhodo- substantiated by great variation in systematically pseudomonas rosea was transferred to Rhodoplanes important molecular structures such as the cytochrome roseus (Hiraishi & Ueda, 1994b). c type structure and the composition of fatty acids and Rhodopseudomonas acidophila quinones (see Pfennig & Tru$ per, 1974; Imhoff & has properties that are Tru$ per, 1989; Imhoff & Bias-Imhoff, 1995). Analysis unique among all of these species (Table 1) and is quite of 16S rDNA sequences demonstrated that some distinct from the type species of this genus, Rhodo- species of the purple non-sulfur bacteria belong to the pseudomonas palustris. In contrast to Rhodo- β-Proteobacteria and that the majority belong to the α- pseudomonas palustris, sulfate is assimilated by Rhodo- Proteobacteria (Gibson et al., 1979; Kawasaki et al., pseudomonas acidophila via adenosine 5h-phospho- 1993; Imhoff & Tru$ per, 1989). Within both subclasses sulfate (Imhoff, 1982), a small-sized, soluble cyto- of the Proteobacteria, the phototrophic bacteria were chrome c# is present (Dickerson, 1980), menaquinones phylogenetically closely related to non-phototrophic, and rhodoquinones are found in addition to purely chemotrophic bacteria. This is also true for ubiquinones and significantly different fatty acids species formerly recognized as Rhodopseudomonas occur (Table 1; see Imhoff & Bias-Imhoff, 1995). species (Pfennig & Tru$ per, 1974), which at that time Furthermore, the lipid A structure is quite different included all rod-shaped, purple non-sulfur bacteria from that of Rhodopseudomonas palustris in having (Woese et al., 1984). only a short chain of sugars and glucosamine as the amino sugar of the backbone instead of 2,3- The recognition of the great diversity within the purple diamino-2,3-dideoxy--glucose (see Weckesser et al., non-sulfur bacteria and also within the genus Rhodo- 1995). DNA–DNA hybridization between Rhodo- pseudomonas led to a number of taxonomic rearrange- pseudomonas palustris and Rhodopseudomonas acido- ments. First of all, the species with vesicular internal phila is less than 15% (Ivanova et al., 1988). The 16S membrane systems were removed from the genus and rDNA sequence of Rhodopseudomonas acidophila is transferred to the genera Rhodobacter and Rhodopila quite different from that of Rhodopseudomonas (Imhoff et al., 1984). Also, Rhodopseudomonas palustris, at least at a level that distinguishes between gelatinosa was transferred to Rhodocyclus gelatinosus Rhodopseudomonas palustris and species of Rhodo- (Imhoff et al., 1984) and later to Rubrivivax gelatinosus planes and Blastochloris and Nitrobacter winogradskyi. (Willems et al., 1991). Later, the marine species of the Finally, Rhodopseudomonas acidophila, in contrast to genus Rhodobacter were transferred to the new genus Rhodopseudomonas palustris, is specifically adapted to Rhodovulum (Hiraishi & Ueda, 1994a), the green- acidic aquatic environments (Pfennig, 1969).
01935 # 2001 IUMS 1863 J. F. Imhoff 8 ) \ 9 n ) 4( n 5 7 2 0 6 5 n n n n n n k j 5–0 n ...... 10, MK-7 8–68 n \ TS, Sulfide Rhodoplanes ), weak growth j ;6, 07 90 n n in is required by some )( 4 (Bd) 67 n 676 21 59 48 52 n n n n n j k 2 5 8 0 5–7 6–0 ( (PAPS) n n 74 Small 3–71 , not determined. n j -2 phototrophic purple α Rhodoplanes roseus )66 ;5, 00 n 06 n 7( n 8–1 n , variable in different strains; ( 6–69 n k \ j )69 57 n 00 n Rhodobium marinum , chemical analysis; tr, trace; jj 0–7 n 8( ...... Niacin Thiamin, p-ABA Biotin, p-ABA Biotin, p-ABA n ;4, and representatives of other )66 17 91 n n ) 0 1 n n 5 9 4 n n n 1( n j kkj j j 0 1 0 9–7 7–0 ( 69 14 n n , negative in most strains; 4–64 n k -phosphosulfate (PAPS). h Rhodobium orientis ;3, )62 56 90 n n ) 7( n j 0–7 7–0 ( n n 2–65 n Rhodopseudomonas palustris , -phosphoadenosine 5 h , Positive in most strains; 90 n 3 (Bd) 65 j kj kjj k k n 7 3 1 2 97 n n n n n \ j . 6–0 (PAPS) n 8–66 n , TS, Sulfide TS Sulfide TS TS j # Rhodopseudomonas palustris H ...... ;2, Rhodoblastus acidophilus 06 30 n n ) 8 (Bd) 64 # n 079 87 23 85 8tr n n n n n aaaaaabb jjj kj kkkjkk kjkkkjjk j (APS) 5–6 0–1 n n -phosphosulfate (APS) or 3 h 2–66 j n Blastochloris sulfoviridis ;8, Rhodoblastus acidophilus C) 25–30 30–37 30–35 25–30 30 30–35 25–30 28–30 m m) 1 size Small Large µ # c Blastochloris viridis C content (mol%) 62 Differential characteristics of j ;7, 18:1 46 18:0 0 16:1 37 16:0 14 14:0 0 Aerobic dark growth Optimum temperature ( Sulfate assimilation* Denitrification Fermentation of fructose Photoautotrophic growth with H Formation of prosthecae Rosette formation ( Cytochrome DNA G Growth factors None p-ABA (biotin) Biotin, p-ABA Colour of culturesBacteriochlorophyll Salt requirement (%)Optimum pH Red to orange-red None Brown-red to red 5 Pink to red None Pink to red 4–5 Pink 1–5 Pink Green to olive-green None Olive-green None None None CharacteristicCell diameter ( 1 2 3 4 5 6 7 8 Major quinones Q-10, MK-10, RQ-10 Q-10 Q-10, MK-10 Q-10, MK-10 Q-10, RQ-10 Q-10, RQ-10 Q-9, MK-9 Q-8 Content of major fatty acids (%): or microaerobic growth only,strains; rosette Q-10, formation ubiquinone observed 10; only MK-10, rarely. menaquinones Abbreviations: 10; p-ABA, RQ-10, p-aminobenzoic rhodoquinone acid; 10; TS, Bd, thiosulfate; buoyant (biotin), density; biot Table 1...... Taxa are identified as: 1, * Sulfate assimilation via adenosine 5 elegans non-sulfur bacteria
1864 International Journal of Systematic and Evolutionary Microbiology 51 Rhodoblastus acidophilus gen. nov., comb. nov.
All of these differences support the placement of the completed by constriction. In the next cycle, both cells two species in different genera. Because Rhodo- form buds at the poles of the former cell division. pseudomonas palustris is the type species of this genus, Under certain conditions, rosettes and clusters are Rhodopseudomonas acidophila has to be transferred to formed. In media lacking calcium ions, cells are non- another genus. Therefore, in accordance with Rules motile. Internal photosynthetic membranes appear as 39a, 39b and 41a of the Bacteriological Code (Lapage lamellae underlying and parallel to the cytoplasmic et al., 1992), the transfer of Rhodopseudomonas membrane. Colour of anaerobic liquid cultures is acidophila to Rhodoblastus acidophilus gen. nov., purple-red to orange-brown. Cells grown under oxic comb. nov., is proposed, which is in line with other conditions are colourless to light pink or orange. taxonomic reclassifications proposed previously and Absorption spectra of living cells show maxima at 375, fully reflects the phylogenetic distance from Rhodo- 460, 490, 525, 590, 805, 855 and 890 nm. Photo- pseudomonas palustris. synthetic pigments are bacteriochlorophyll a (esterified with phytol) and carotenoids of the spirilloxanthin series with glucosides of rhodopin and rhodopinal. Description of Rhodoblastus gen. nov. The latter are characteristic of this species. Photo- Rhodoblastus (Rho.do.blashtus. Gr. n. rhodon the rose; heterotrophic growth with a number of organic carbon Gr. n. blastos bud shoot; N.L. masc. n. Rhodoblastus sources is the preferred mode of growth. Photo- the budding rose, referring to the cell colour and the autotrophic growth is possible with hydrogen as mode of cell division). electron donor; sulfide and thiosulfate cannot be used. Cells grow chemoautotrophically under microoxic to Cells are rod-shaped, motile by means of flagella, show oxic conditions in the dark with hydrogen as electron polar growth, budding and asymmetric cell division. donor. Organic carbon sources used are acetate, Gram-negative and belong to the α-2 proteobacteria. propionate, butyrate, lactate, pyruvate, fumarate, Internal photosynthetic membranes appear as lamellae malate, succinate, valerate, formate, methanol and underlying and parallel to the cytoplasmic membrane. ethanol. Not used are caprylate, pelargonate, glycerol, Photosynthetic pigments are bacteriochlorophyll a and benzoate, sugars, sugar alcohols, glutamate and other carotenoids. Straight-chain monounsaturated C"):" amino acids. Sulfate can be assimilated. Nitrogen and C"':" and saturated C"':! are the major cellular sources are ammonia, dinitrogen and some amino fatty acids. Contain ubiquinones, rhodoquinones and acids. Growth factors are not required; yeast extract menaquinones with 10 isoprene units (Q-10, MK-10 and other complex nutrients do not increase the growth and RQ-10). Preferred mode of growth is photo- rate. Ubiquinones, menaquinones and rhodoquinones heterotrophic under anoxic conditions in the light. with 10 isoprene units (Q-10, MK-10, RQ-10) are Photoautotrophic growth may be possible under present. Mesophilic freshwater bacterium with op- anoxic conditions with hydrogen as the electron donor. timum growth at 25–30 mC and pH 5n5–6n0. The GjC Chemotrophic growth occurs under microoxic to oxic content of the DNA is 62n2–66n8 mol% (buoyant conditions, but with some substrates also occurs density). anaerobically by fermentation. Growth factors are not T T The type strain is ATCC 25092 (lDSM 137 required by the type species. Mesophilic freshwater T bacteria with a preference for acidic pH. Habitat is lPfennig 7050 ). The EMBL accession number of the 16S rDNA sequence of the type strain is M34128. slightly acidic freshwater ponds. The GjC content of the DNA is 62n2–66n8 mol% (buoyant density). References The type species is Rhodoblastus (Rbl.) acidophilus (basonym Rhodopseudomonas acidophila Pfennig 1969, Dickerson, R. E. (1980). Evolution and gene transfer in purple 601AL). photosynthetic bacteria. Nature 283, 210–212. Gibson, J., Stackebrandt, E., Zablen, L. B., Gupta, R. & Woese, C. R. (1979). A phylogenetic analysis of the purple photo- Description of Rhodoblastus acidophilus comb. nov. synthetic bacteria. Curr Microbiol 3, 59–64. Rhodoblastus acidophilus acidus Hiraishi, A. (1997). Transfer of the bacteriochlorophyll b- (a.ci.dohphi.lus. 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