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1 State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Zhong-Guan-Cun, Haidian, Beijing 100080, P. R. China
2 Graduate University of Chinese Academy of Sciences, Beijing 100049, P. R. China
Correspondence
Shuang-Jiang Liu
liusj{at}sun.im.ac.cn
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ABSTRACT |
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7c (64.2 %). The sole respiratory quinone was ubiquinone-10. The G+C content of the genomic DNA was 61.3 mol% (Tm). 16S rRNA gene sequence analysis indicated that strain LW36T was phylogenetically related to members of the genus Paracoccus, with similarities ranging from 92.4 to 94.9 %. Based on these results, it is concluded that strain LW36T represents a novel species of the genus Paracoccus, for which the name Paracoccus sulfuroxidans is proposed. The type strain is strain LW36T (=CGMCC 1.5364T=JCM 14013T).
A scanning electron micrograph of cells of strain LW36T and a table showing its cellular fatty acid profile are available as supplementary material in IJSEM Online.
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and the description was emended by Katayama et al. (1995). At the time of writing, the genus comprises 19 recognized species (see Fig. 1). Members of this genus are metabolically versatile and are widely distributed in soil, sediment and activated sludge environments. They take part in bioconversion of organic and inorganic compounds. For example, Paracoccus denitrificans utilizes organic compounds for growth and can use nitrate for respiration (Rainey et al., 1999, and references therein). Some other Paracoccus species, such as Paracoccus pantotrophus (Robertson & Kuenen, 1983; Rainey et al., 1999), Paracoccus thiocyanatus and Paracoccus versutus, can use reduced sulfur as an energy source (Harrison, 1983; Katayama et al., 1995). In this study, a sulfur-oxidizing, heterotrophic bacterial strain, designated LW36T, was isolated from activated sludge. Based on phenotypic and genotypic studies it is concluded that this isolate represents a novel species of the genus Paracoccus.
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Routine cultivation was conducted at 30 °C with LB media. Gram reactions were determined according to the method described by Gerhardt et al. (1994). Presence of cell flagella and cell morphology were examined by transmission electron microscopy (H600; Hitachi) and scanning electron microscopy (FEI QUANTA 200). Growth temperature range was determined with a TN3F temperature-gradient incubator (Advantec). Catalase and oxidase activities, the Voges–Proskauer reaction, carbon source utilization and other biochemical characterization methods were performed according to Dong & Cai (2001). For testing growth on reduced sulfur and elemental sulfur, strain LW36T was inoculated into Allen's medium (Allen, 1959), the pH of which was adjusted to 6.5, supplemented with elemental sulfur (1 %), sulfide (1 %), thiosulfate (1 %) or sulfite (1 %). Cell growth was estimated either by monitoring the increase in optical density at 600 nm or by determining the increase in protein content of cultures.
Cells of strain LW36T were Gram-negative, coccoid to short rods with a size range of 1.0–1.2x0.5 µm (see Supplementary Fig. S1 in IJSEM Online). Colonies were cream-coloured, smooth, circular and 0.4–2.0 mm in diameter. Growth was observed over a temperature range of 25–36 °C and a pH range of 5–10. Strain LW36T grew chemolithotrophically on thiosulfate, sulfide and elemental sulfur but growth was not observed with sulfite. Other physiological and biochemical characteristics are given in Table 1 and in the species description below.
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. Quinones were extracted and purified according to the method of Collins (1985) and were analysed by HPLC (Wu et al., 1989), with a commercial ubiquinone-10 (Q-10) sample (China Pharmacy Corp.) as reference. Results showed that the major cellular fatty acids (>1 % of the total) of strain LW36T were C18 : 17c (64.2 %), C16 : 0 (16.4 %), C18 : 0 (3.7 %), C14 : 0 3-OH (3.0 %), C16 : 17c (2.3 %), C14 : 0 (1.9 %), iso-C15 : 1 (1.8 %) and C19cyc (1.4 %). Detailed information on the cellular fatty acid composition of strain LW36T is provided in Supplementary Table S1 in IJSEM Online. Strain LW36T had Q-10 as the sole respiratory quinone. DNA base composition was determined by thermal denaturation (Marmur & Doty, 1962), with Escherichia coli K-12 as reference. The DNA G+C content of strain LW36T was 61.3 mol%.
The nearly complete 16S rRNA gene of strain LW36T (1343 bp) was amplified and sequenced as described by Zhang et al. (2003). Alignments of 16S rRNA gene sequences were performed with the CLUSTAL_X program, version 1.64b (Thompson et al., 1997). A neighbour-joining (Saitou & Nei, 1987) phylogenetic tree (Fig. 1
) was constructed based on evolutionary distances calculated with the Kimura two-parameter model. When aligned, positions with insertions or deletions were excluded from the calculations. The 16S rRNA gene sequence analysis indicated that strain LW36T was phylogenetically related to members of the genus Paracoccus, with similarities ranging from 92.4 to 94.9 %.
Based on our phenotypic and phylogenetic studies, it is clear that strain LW36T represents a member of the genus Paracoccus. Strain LW36T showed a range of phenotypic characteristics that differentiated it from recognized species of the genus (as listed in Table 1). Its phylogenetic divergence (Fig. 1) also differentiates strain LW36T from recognized Paracoccus species. Therefore, we conclude that strain LW36T represents a novel species of the genus Paracoccus, for which the name Paracoccus sulfuroxidans sp. nov. is proposed.
Description of Paracoccus sulfuroxidans sp. nov.
Paracoccus sulfuroxidans (sul.fur.ox'i.dans. L. n. sulfur sulfur; N.L. part. adj. oxidans oxidizing; N.L. part. adj. sulfuroxidans pertaining to the ability to oxidize sulfur).
Cells are Gram-negative, coccoid to short rods, 1.0–1.2x0.5 µm in size. Colonies are cream-coloured, smooth, circular and 0.4–2.0 mm in diameter. Growth occurs over a temperature range of 25–36 °C (optimum growth at 31.5–33.5 °C) and a pH range of 5–10. Positive for catalase and oxidase activities. Negative for Voges–Proskauer reaction and lipase activity. Does not hydrolyse gelatin, starch or casein. Utilizes citric acid, nitrilosides, L-arabinose, D-glucose and maltose, but not D-arabitol, fructose, mannitol, rhamnose, melibiose, xylitol, malic acid, L-glutamic acid, L-lactic acid, cellobiose, D-lactose, inositol, D-mannose, D-melibiose, raffinose, D-ribose, salicin, sorbitol, glycerol, trehalose or dextrin. Grows chemolithotrophically on thiosulfate, sulfide and elemental sulfur but not on sulfite. The sole respiratory quinone is Q-10. The predominant cellular fatty acid is C18 : 17c (64.2 %). The G+C content of the DNA is 61.3 mol% (Tm).
The type strain, LW36T (=CGMCC 1.5364T=JCM 14013T), was isolated from activated sludge of a wastewater-treatment bioreactor.
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ACKNOWLEDGEMENTS |
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REFERENCES |
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Collins, M. D. (1985). Isoprenoid quinone analysis in classification and identification. In Chemical Methods in Bacterial Systematics, pp. 267–287. Edited by M. Goodfellow & D. E. Minnikin. London: Academic Press.
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Dong, X.-Z. & Cai, M.-Y. (editors) (2001). Determination of biochemical properties. In Manual for Systematic Identification of General Bacteria, pp. 370–398. Beijing: Science Press.
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Harrison, A. P., Jr (1983). Genomic and physiological comparisons between heterotrophic thiobacilli and Acidiphilium cryptum, Thiobacillus versutus sp. nov., and Thiobacillus acidophilus nom. rev. Int J Syst Bacteriol 33, 211–217.
Hu, Y.-T., Zhou, P.-J., Zhou, Y.-G., Liu, Z.-H. & Liu, S.-J. (2004). Saccharothrix xingjiangensis sp. nov., a pyrene-degrading actinomycete isolated from Tianchi Lake, Xinjiang, China. Int J Syst Evol Microbiol 54, 2091–2094.
Katayama, Y., Hiraishi, A. & Kuraishi, H. (1995). Paracoccus thiocyanatus sp. nov., a new species of thiocyanate-utilizing facultative chemolithotroph, and transfer of Thiobacillus versutus to the genus Paracoccus as Paracoccus versutus comb. nov. with emendation of the genus. Microbiology 141, 1469–1477.
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Robertson, L. A. & Kuenen, J. G. (1983). Thiosphaera pantotropha gen. nov. sp. nov., a facultatively anaerobic, facultatively autotrophic sulphur bacterium. J Gen Microbiol 129, 2847–2855.
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