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1 Korea Research Institute of Bioscience and Biotechnology, 52 Oeundong, Yusong, Daejeon 305-333, Republic of Korea
2 Division of Applied Life Science, EB-NCRC, PMBBRC, Gyeongsang National University, Jinju, 660-701, Republic of Korea
3 Health Industry Center, Chungcheongbuk-Do 363-883, Republic of Korea
4 Rural Resources Development Institute of Agricultural Science and Technology, Rural Development Administration, Suwon 411-853, Korea
Correspondence
Chang-Jin Kim
changjin{at}kribb.re.kr
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ABSTRACT |
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7c and 11-methyl C18 : 17c. The genomic DNA G+C content was 72.0 mol% and the predominant lipoquinone was Q-10. The major cellular phospholipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain DS2T formed a distinct phyletic line from the genus Rubrimonas within the Alphaproteobacteria. The levels of 16S rRNA gene sequence similarity with respect to the type strains of related genera were below 94 %. On the basis of physiological and phylogenetic properties, strain DS2T represents a novel genus and species of the Alphaproteobacteria, for which the name Albimonas donghaensis gen. nov., sp. nov. is proposed. The type strain is DS2T (=KCTC 12586T=DSM 17890T).
These authors contributed equally to this work. 
The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain DS2T is DQ280370.
A transmission electron micrograph of cells of strain DS2T is available as a supplementary figure with the online version of this paper.
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reported on aerobic methylotrophs containing bacteriochlorophyll a, a range of aerobic, anoxygenic, phototrophic bacteria have been described (Imhoff et al., 1984; Hiraishi & Ueda, 1995; Suzuki et al., 1999, 2006; Albuquerque et al., 2002; Sorokin et al., 2005; Biebl et al., 2007). However, a non-pigmented micro-organism, Albidovulum inexpectatum, which is closely related to the genera Rhodovulum, Thioclava and Rhodobacter but does not produce bacteriochlorophyll a, was isolated recently from a marine hot spring (Albuquerque et al., 2002). In this study, we also isolated (from seawater of the East Sea in Korea) a slightly halophilic non-pigmented bacterium that did not produce bacteriochlorophyll a. The isolate was not phototrophic but 16S rRNA gene sequence analysis showed that it was closely related to the genus Rubrimonas and analysis of phylogenetic and chemotaxonomic characteristics indicated that the isolate represented a new genus of the class Alphaproteobacteria.
Strain DS2T was isolated from seawater from the East Sea in Korea by means of the serial dilution plating method, using incubation on marine agar 2216 (MA; Difco) at 28 °C for 3 days. Subcultivation was done on MA at 30 °C for 2–3 days. NaCl requirements and tolerance were determined in nutrient broth (Difco) supplemented with modified artificial seawater containing (l–1): 0–20 % (w/v) NaCl (increments of 1 %), 5.94 g MgSO4 . 7H2O, 4.53 g MgCl2 . 6H2O, 0.64 g KCl and 1.3 g CaCl2. Growth was tested at different temperatures (4–50 °C) and pH values (5.0–10.0) in marine broth (Gomori, 1955). Cell morphology and flagellation were investigated using light microscopy and transmission electron microscopy (JEM-1010; JEOL), as described previously (Jeon et al., 2005). Gram staining was determined using the bioMérieux Gram stain kit according to the manufacturer's instructions. Oxidase activity was tested using a Bactident oxidase strip (Merck) and catalase activity was determined by assessing bubble production in a 3 % (v/v) hydrogen peroxide solution. Nitrate reduction and the hydrolysis of aesculin, casein, gelatin, starch, Tween 80, L-tyrosine and urea were determined on MA according to the methods described by Cowan & Steel (1965), Lanyi (1987) and Gerhardt et al. (1994). Acid production from D-galactose, D-glucose, D-lactose, L-arabinose, D-fructose, D-ribose, D-xylose and sucrose was determined as described by Leifson (1963). Growth under anaerobic conditions was determined after 5 days incubation on MA at 30 °C in an anaerobic chamber. Strain DS2T formed creamy, smooth, convex, glistening and circular/slightly irregular colonies on MA at 30 °C after 2 days incubation. The strain grew at NaCl concentrations in the range 0–14 % (w/v) and showed optimum growth at 2–5 % (w/v) NaCl. Growth occurred from pH 6.0 to pH 9.5 (optimum, pH 7.0–8.0) in marine broth. Growth was observed at temperatures between 10 and 38 °C, the optimum growth temperature being 28–30 °C. The cells of strain DS2T were Gram-negative, strictly aerobic, non-motile rods 1.0–1.4 µm in width and 1.6–2.6 µm in length (see Supplementary Fig. S1, available in IJSEM Online). The strain showed oxidase- and catalase-positive reactions and did not reduce nitrate to nitrite. It hydrolysed gelatin and urea, but hydrolysis of aesculin, casein, L-tyrosine, starch and Tween 80 was not observed.
Whole-cell fatty acids of strain DS2T were analysed according to the instructions of the Microbial Identification System (MIDI; Microbial ID) after cultivation on MA for 2 days at 30 °C. The DNA G+C content (mol%) was determined by reversed-phase HPLC using the method of Tamaoka & Komagata (1984). Analyses of isoprenoid quinones and polar lipids were carried out using the methods described by Komagata & Suzuki (1987). The major cellular fatty acids of strain DS2T (on MA) were C18 : 17c (53.48 %), 11-methyl C18 : 17c (21.19 %), C18 : 0 (7.69 %) and C16 : 0 (6.28 %) (Table 1), being different from those of the genus Rubrimonas (which is, at the time of writing, the most closely related genus). Strain DS2T was found to have high levels of the fatty acids C18 : 17c (53.48 %) and 11-methyl C18 : 17c (21.19 %), whereas these fatty acid components were not detected, even in trace amounts, in the cell membrane of Rubrimonas cliftonensis OCh 317T (Table 1). The genomic DNA G+C content of strain DS2T was 72.0 mol% and the predominant isoprenoid quinone was Q-10. The strain contained phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine as the major polar lipids. The typical phenotypic and chemotaxonomic properties of strain DS2T are compared with those of the closest phylogenetic relative, Rubrimonas cliftonensis, in Table 2, many of which allow the differentiation of strain DS2T from the genus Rubrimonas.
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) and then sequenced. The resultant 16S rRNA gene sequence (1383 nt) was compared with 16S rRNA gene sequences available from GenBank, using the BLAST program (http://www.ncbi.nlm.nih.gov/BLAST/) to determine an approximate phylogenetic affiliation, and gene sequences were aligned with those of closely related species using CLUSTAL W software (Thompson et al., 1994). Phylogenetic trees were constructed using three different methods, i.e. the neighbour-joining, maximum-likelihood and maximum-parsimony algorithms available in PHYLIP, version 3.6 (Felsenstein, 2002). Using the FASTA3 program in EBI Tools (http://www.ebi.ac.uk/fasta33/), 16S rRNA gene sequence comparisons for similarity calculations were made between strain DS2T and related organisms. A bootstrap analysis was performed according to the algorithm of the Kimura two-parameter model (Kimura, 1980) of the neighbour-joining method in the PHYLIP package. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain DS2T formed a distinct phylogenetic lineage with respect to the most closely related genus, Rubrimonas (class Alphaproteobacteria), with 69 % bootstrap support (Fig. 1). The topologies of the phylogenetic trees built using the maximum-likelihood and maximum-parsimony algorithms also supported the notion that the isolate could represent a phylogenetic genus that was distinct from the most closely related genera (data not shown). A comparative analysis of 16S rRNA gene sequences showed that the levels of sequence similarity between strain DS2T and the type strains of related genera were below 94 %. On the basis of physiological and molecular data, strain DS2T represents a novel genus and species within the class Alphaproteobacteria, for which the name Albimonas donghaensis gen. nov., sp. nov. is proposed.
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Colonies are not pigmented. Nitrate is not reduced to nitrite. Cells are non-motile, non-spore-forming, short rods. Catalase- and oxidase-positive. Bacteriochlorophyll a is not synthesized under aerobic conditions. Major fatty acids are C18 : 17c and 11-methyl C18 : 17c. Major isoprenoid quinone is Q-10. Predominant polar lipids are phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The type species is Albimonas donghaensis.
Description of Albimonas donghaensis sp. nov.
Albimonas donghaensis (dong.ha.en'sis. N.L. fem. adj. donghaensis belonging to Donghae, where the organism was isolated).
Colonies are smooth, glistening, circular and slightly irregular and cream in colour. Cells are strictly aerobic, Gram-negative and approximately 1.0–1.4 µm wide and 1.6–2.6 µm long. Growth occurs between 10 and 38 °C (optimally at 28–30 °C) and from pH 6.0 to pH 9.5 (optimally at pH 7.0–8.0). Cells grow at salinities of 0–14 % (w/v) NaCl (optimally at 2–5 %, w/v). Gelatin and urea are hydrolysed, but hydrolysis of aesculin, casein, starch, L-tyrosine and Tween 80 is not observed. Acid is produced from L-arabinose and D-xylose, but not from D-galactose, D-glucose, D-fructose, lactose, D-ribose or sucrose. Negative for indole and H2S production and in the ONPG reaction. Voges–Proskauer test is positive (weak). Alkaline phosphatase, esterase (C4), esterase lipase (C8), leucine arylamidase and acid phosphatase are produced, but lipase (C14), valine arylamidase, cystine arylamidase, trypsin, 
-chymotrypsin, -galactosidase, β-galactosidase, β-glucuronidase, -glucosidase, β-glucosidase, N-acetyl-β-glucosaminidase, -mannosidase and -fucosidase are not produced. Naphthol-AS-BI-phosphohydrolase activity is weak. The G+C content of the genomic DNA of the type strain is 72.0 mol% (HPLC).
The type strain, DS2T (=KCTC 12586T=DSM 17890T), was isolated from seawater from the East Sea in Korea.
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ACKNOWLEDGEMENTS |
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Biebl, H., Pukall, R., Lünsdorf, H., Schulz, S., Allgaier, M., Tindall, B. J. & Wagner-Döbler, I. (2007). Description of Labrenzia alexandrii gen. nov., sp. nov., a novel alphaproteobacterium containing bacteriochlorophyll a, and a proposal for reclassification of Stappia aggregata as Labrenzia aggregata comb. nov., of Stappia marina as Labrenzia marina comb. nov. and of Stappia alba as Labrenzia alba comb. nov., and emended descriptions of the genera Pannonibacter, Stappia and Roseibium, and of the species Roseibium denhamense and Roseibium. Int J Syst Evol Microbiol 57, 1095–1107.
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