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Int J Syst Evol Microbiol 53 (2003), 971-975; DOI  10.1099/ijs.0.02373-0
© 2003 International Union of Microbiological Societies

Alkaliphilus crotonatoxidans sp. nov., a strictly anaerobic, crotonate-dismutating bacterium isolated from a methanogenic environment

Xianhua Cao, Xiaoli Liu and Xiuzhu Dong

State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, People's Republic of China

Correspondence
Xiuzhu Dong
dongxz{at}sun.im.ac.cn


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Two bacterial strains were isolated from methanogenic butyrate-oxidizing mixed cultures. The cells were straight to slightly curved, Gram-positive rods that were motile by means of multiple flagella and formed endospores. Growth was observed in the temperature range 15–45 °C (optimum 37 °C) and pH range 5·5–9·0 (optimum pH 7·5). The novel isolates were strictly anaerobic chemo-organotrophs capable of utilizing yeast extract, peptone, tryptone and a variety of sugars and organic acids, but not glucose. None of the accessory electron acceptors tested (elemental sulfur, thiosulfate or fumarate) improved growth, except crotonate, which was dismutated to butyrate and acetate. The G+C content of the DNA of one of the isolates, strain B11-2T, was 30·6 mol%. Phylogenetic analysis based on 16S rDNA sequence similarity between strain B11-2T and some other strictly anaerobic, spore-forming bacteria indicated that the novel isolates represented a species in cluster XI within the low-GC Gram-positive bacteria, being most closely related to Alkaliphilus transvaalensis JCM 10712T. DNA–DNA relatedness between strain B11-2T and A. transvaalensis JCM 10712T was 21 %. On the basis of physiological and molecular properties, and cellular fatty acid and cell wall compositions, the novel isolates are proposed to represent a novel species of the genus Alkaliphilus, for which the name Alkaliphilus crotonatoxidans is proposed (type strain B11-2T=AS 1.2897T=JCM 11672T).

The GenBank/EMBL/DDBJ accession number for the 16S rDNA sequence of Alkaliphilus crotonatoxidans B11-2T is AF467248.


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In methanogenic environments, butyrate can be converted to methane and acetate only by the concerted action of syntrophic bacteria and methanogens because of energetic difficulties (Schink, 1992Go, 1997Go; Stams, 1994Go). In the syntrophic degradation of butyrate and benzoate, crotonate is a very important intermediate involved in the energetically unfavourable step (Wofford et al., 1986Go; Schink, 1992Go). Some syntrophs, such as Syntrophomonas wolfei (Beaty & McInerney, 1987Go) and Syntrophospora bryantii (Zhao et al., 1990Go), can grow on crotonate without H2-consuming partners. During the investigation of butyrate- and benzoate-degrading syntrophic bacteria from methanogenic environments, a few butyrate-degrading tricultures have been isolated. These tricultures degraded butyrate to acetate and methane, and contained some spore-forming rods, which were observed microscopically. These spore-forming bacteria constantly occurred in fluorescent colonies observed under UV light (420 nm) and did not degrade butyrate in co-culture with a methanogen; however, they dismutated crotonate to acetate and butyrate. In this report, the isolation and characterization of the crotonate-dismutating, spore-forming bacteria from butyrate-oxidizing consortia are described.

Strains B11-2T and LE-9 were isolated from methanogenic butyrate-degrading consortia which were enriched from an anaerobic digester for treating the wastewater of a bean curd farm (Beijing, China). After being purified in a crotonate-containing pre-reduced basal medium (McInerney et al., 1979Go) by the Hungate roll-tube technique (Hungate, 1969Go), single colonies were cultured in the same medium under a gas phase of N2/CO2 (80 : 20) at 37 °C.

C2–C6 fatty acids, crotonate and CH4 were detected by GC (GC-14B; Shimadzu). Whole-cell fatty acids were analysed as fatty acid methyl esters with a MIDI microbial identification system. Cell wall compositions were identified using the method of Staneck & Roberts (1974)Go.

DNA was prepared and purified as described by Marmur (1961)Go and the 16S rDNA of strain B11-2T was amplified by PCR using genomic DNA as template. The universal primers Bac 27F and 1541R were complementary to positions 8–27 and 1525–1541, respectively, of the 16S rDNA of Escherichia coli (Winker & Woese, 1991Go). Sequencing of the 16S rDNA was done by TaKaRa using ABI PRISM Big Dye Terminator Cycle Sequencing Ready Reaction kits (Perkin Elmer) and an ABI PRISM 377XL DNA sequencer. The complete 16S rDNA sequence of strain B11-2T and those of its closest relatives obtained from GenBank were aligned using CLUSTAL W software (version 1.5). Similarity values were calculated and converted to a distance matrix using the Jukes–Cantor coefficient within the DNADIST program, and a phylogenetic tree was constructed using the neighbour-joining method (PHYLIP, version 3.5; Felsenstein, 1993Go).

The G+C content of the DNA of strain B11-2T was determined by thermal denaturation (Marmur & Doty, 1962Go). DNA from Escherichia coli K-12 was used as a reference for the determination of the thermal melting profile. The DNA–DNA liquid reassociation rate between strain B11-2T and Alkaliphilus transvaalensis JCM 10712T was determined at 63 °C, as described previously (De Ley et al., 1970Go).

Cells of strains B11-2T and LE-9 were straight to slightly curved rods (2·0–3·0x0·4–0·6 µm) that stained Gram-positive and possessed multiple flagella. In the late-exponential and stationary phases of growth, the rods tended to form chains of 4–6 cells in length and swelled to form terminal spherical spores (Fig. 1Go).



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  		Fig. 1. Transmission electron micrograph (obtained using an Hitachi H-500 electron microscope) of strain B11-2T. Bar, 1 µm.

 
The generation time of strain B11-2T was 3·29 h when grown anaerobically in crotonate/basal medium at 37 °C. However, growth was completely inhibited by air. Strains B11-2T and LE-9 grew mesophilically and neutrally (Table 1Go). They also grew in media containing complex proteinaceous substrates such as yeast extract, peptone and tryptone as sole energy source, but not glucose. Growth on proteinaceous substrates was significantly improved by the addition of 10 mM crotonate and other organic substrates, but not by other electron acceptors such as fumarate, sulfur and thiosulfate (Table 1Go).


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  		Table 1. Differentiating physiological and biochemical characteristics of strains B11-2T and LE-9 and Alkaliphilus transvaalensis JCM 10712T

For all growth experiments, a basal medium containing 10 mM crotonate plus 0·25 % yeast extract was used. Growth was measured using a spectrophotometer at a wavelength of 600 nm. A substrate was deemed to be utilized when a higher OD600 value was obtained from the yeast extract/basal medium with the substrate than without it after culturing the strain at 37 °C for 7 days; utilization was confirmed by growing the strain in the same substrate for three subcultures. All experiments were performed in duplicate. Elemental sulfur, thiosulfate, fumarate and other substrates were tested at a final concentration of 10 mM in basal medium. +, Positive; -, negative; ND, not determined.

 
When cultivated at 37 °C for 3 days with yeast extract, strain B11-2T dismutated 10 mM crotonate to 7 mM acetate and 4·5 mM butyrate, values about 20 % lower than the theoretical stochiometrical values (10 mM acetate plus 5 mM butyrate). Since strains B11-2T and LE-9 were originally isolated from a methanogenic butyrate-degrading mixed culture, their abilities to degrade butyrate in a methanogenic consortium were tested. An artificial co-culture was constructed as described previously (Dong et al., 1994Go) by adding 10 ml of a crotonate-grown culture of strain B11-2T to 20 ml of H2/CO2-grown Methanospirillum hungatei DSM 864T, an efficient H2-consumer, to remove H2 inhibition for butyrate degradation. The gas phase was changed to N2/CO2 (80 : 20) and 20 mM butyrate was added to the co-culture. However, after cultivation at 37 °C for 4 weeks, the co-culture did not degrade butyrate at all (data not shown). The most probable explanation for the presence of strains B11-2T and LE-9 in the syntrophic butyrate-degrading consortia is that they use crotonate as a substrate, which is one of the important intermediates involved in the energetically unfavourable step in butyrate degradation (Wofford et al., 1986Go; Schink, 1992Go). Since strain B11-2T is difficult to remove from the mixed culture, its role in butyrate degradation can only be clarified when the co-culture is characterized in its absence.

To determine the phylogenetic relationship of strain B11-2T (and LE-9) with other bacteria, a dendrogram based on 16S rDNA sequence data was constructed (Fig. 2Go). Strain B11-2T grouped in cluster XI within the low-GC Gram-positive bacteria, and was most closely related to Alkaliphilus transvaalensis JCM 10712T (Takai et al., 2001Go) and other alkaliphilic spore-forming anaerobes (Cato et al., 1986Go; Collins et al., 1994Go; Rainey & Stackebrandt, 1993Go). The 16S rDNA sequence similarity values of strain B11-2T to A. transvaalensis JCM 10712T, Clostridium aceticum DSM 1496T (Stackebrandt et al., 1999Go), Clostridium felsineum DSM 794T (Collins et al., 1994Go) and Clostridium paradoxum DSM 7308T (Rainey et al., 1996Go) were 97, 94, 93 and 91 %, respectively. As strain B11-2T was most closely related to A. transvaalensis JCM 10712T phylogenetically, DNA–DNA relatedness between these strains was determined. A low DNA–DNA reassociation rate (21 %) was measured, which is lower than the species-defining threshold (70 % DNA homology) described by Wayne et al. (1987)Go.



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  		Fig. 2. Phylogenetic tree based on a multiple alignment of 1280 bp fragments of 16S rDNA sequences. The tree, rooted using the 16S rDNA sequence of Bacillus subtilis, was constructed by the neighbour-joining method. Bootstrap values are shown at the branch points, and are expressed as a percentage of 1000 replications. 16S rDNA sequence GenBank accession numbers are shown in parentheses. Bar, 5 % sequence divergence.

 
Furthermore, the cell wall compositions of strain B11-2T and A. transvaalensis JCM 10712T were determined to be the same, i.e. both strains had meso-diaminopimelic acid, glycine, aspartate, glutamate and ribose. This composition differed from that observed in the phylogenetically related genus Clostridium, in which glutamate is not detected in most species. The cellular fatty acids of strain B11-2T and A. transvaalensis JCM 10712T are shown in Table 2Go. Obviously, straight-chain or branched-chain saturated fatty acids (C14–C16) are the predominant fatty acids; these are also observed in thermophilic clostridia (Chan et al., 1971Go). Whereas iso-C15 : 0 (42·6 %), C14 : 0 (24·4 %) and C16 : 0 (12·3 %) were the main fatty acids of A. transvaalensis JCM 10712T, C14 : 0 (45·6 %) and C16 : 0 (17·4 %) were the major fatty acids in strain B11-2T and iso-C15 : 0 (7·1 %) and anteiso-C15 : 0 (7·5 %) were present in moderate amounts. In the assay used in this study, some branched fatty acids, such as iso-C15 : 1{omega}7c, iso-C17 : 1{omega}7c and iso-C17 : 0, were not detected in A. transvaalensis JCM 10712T because of the different culture medium used compared to that used by Takai et al. (2001)Go.


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  		Table 2. Cellular fatty acid compositions of Alkaliphilus crotonatoxidans B11-2T and A. transvaalensis JCM 10712T

For the assay of cellular fatty acids, the biomasses of both strains were harvested from crotonate-grown cultures after cultivation at 37 °C for 72 h; the culture medium was at pH 7·5 for A. crotonatoxidans B11-2T and at pH 8·5 for A. transvaalensis JCM 10712T. ND, Not detected. All values are expressed as a percentage of the total fatty acid composition.

 
Table 1Go lists the different physiological and biochemical characteristics of strains B11-2T and LE-9 and A. transvaalensis JCM 10712T. Although A. transvaalensis JCM 10712T is an extreme alkaliphile, the neutral strain B11-2T is closely related to it in terms of phylogenetic, chemotaxonomic and some physiological characteristics, such as utilization of only proteinaceous substrates as sole energy sources. However, strains B11-2T and LE-9 differ from A. transvaalensis JCM 10712T in their sugar-fermenting patterns and G+C content (by 5·8 mol%). Therefore, on the basis of the data presented here, it is proposed that strains B11-2T and LE-9 represent a novel species of the genus Alkaliphilus, namely Alkaliphilus crotonatoxidans.

In the phylogenetic tree, strain B11-2T clustered with some alkaliphiles suggesting that it might be derived from an alkalitrophic lineage and has gradually lost its alkaline-prone characteristics by living in a neutral niche for a long time.

Description of Alkaliphilus crotonatoxidans sp. nov.
Alkaliphilus crotonatoxidans (cro.to.nat.ox'i.dans. N.L. part. adj. crotonatoxidans of the one that oxidizes crotonate).

Gram-positive, straight to slightly curved rods (2·0–3·0x0·4–0·6 µm). Cells occur singly or in chains. Vegetative cells swell to form terminal spherical spores. Motile by means of multiple flagella. Cell wall contains meso-diaminopimelic acid, glycine, aspartate, glutamate and ribose. The cellular fatty acid composition comprises major amounts of C14 : 0 and C16 : 0 and moderate amounts of iso-C13 : 0, C13 : 1{omega}2c, iso-C15 : 0, anteiso-C15 : 0, C16 : 1{omega}7c and anteiso-C17 : 0. Strictly anaerobic. The temperature range for growth is 15–45 °C, with optimum growth at 37 °C. The pH range for growth is 5·5–9·0, with optimum growth at approximately pH 7·5. Growth occurs with yeast extract, peptone, tryptone, fructose, cellobiose, maltose, trehalose, xylose, ribose, citrate, malate and crotonate, but not with glucose, lactose, sucrose, galactose, lactate, succinate, butyrate or acetate. Dismutates crotonate to acetate and butyrate. Growth is not stimulated in the presence of other electron acceptors such as fumarate, sulfur and thiosulfate.

The type strain is B11-2T (=AS 1.2897T=JCM 11672T). The G+C content of its genomic DNA is 30·6 mol%.

Emended description of the genus Alkaliphilus
Straight to slightly curved rods that are motile by means of flagella, Gram-positive and spore-forming. Anaerobic. Neutrophilic or alkaliphilic heterotrophs. Utilize only proteinaceous substrates such as yeast extract, peptone and tryptone as sole energy source. G+C content of genomic DNA is in the range 30–36 mol%. Cell walls contain meso-diaminopimelic acid, glycine, aspartate, glutamate and ribose. Members of the genus are characterized by fatty acid profiles that contain straight-chain acids and branched acids. Predominant fatty acids are C14 : 0 and C16 : 0 or C14 : 0, iso-C15 : 0 and C16 : 0. On the basis of 16S rRNA gene sequence analyses, the genus is most closely related to the genera Clostridium and Tindallia and is a member of cluster XI within the low-GC Gram-positive group of bacteria. The type species of the genus is Alkaliphilus transvaalensis.


   ACKNOWLEDGEMENTS
 
This study was supported by grants from the China National Foundation of Sciences (no. 30025001) and the Chinese Academy of Sciences. We thank Yajun Song (Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences) for assistance with the assay of cellular fatty acids and Yamei Zhang (Institute of Microbiology, Chinese Academy of Sciences) for assistance with the measurement of cell wall compositions.


   REFERENCES
TOP
 ABSTRACT
 MAIN TEXT
 REFERENCES
 
Beaty, P. S. & McInerney, M. J. (1987). Growth of Syntrophomonas wolfei in pure culture on crotonate. Arch Microbiol 147, 389–393.[CrossRef]

Cato, E. P., George, W. L. & Finegold, S. M. (1986). Genus Clostridium Prazmowski 1880, 23AL. In Bergey's Manual of Systematic Bacteriology, vol. 2, pp. 1141–1200. Edited by P. H. A. Sneath, N. S. Mair, M. E. Sharp & J. G. Holt. Baltimore: Williams & Wilkins.

Chan, M., Himes, R. H. & Akagi, J. M. (1971). Fatty acid composition of thermophilic, mesophilic, and psychrophilic clostridia. J Bacteriol 106, 876–881.[Abstract/Free Full Text]

Collins, M. D., Lawson, P. A., Willems, A., Cordoba, J. J., Fernandez-Garayzabal, J., Garcia, P., Cai, J., Hippe, H. & Farrow, J. A. E. (1994). The phylogeny of the genus Clostridium: proposal of five new genera and eleven new species combinations. Int J Syst Bacteriol 44, 812–826.[Abstract/Free Full Text]

De Ley, J., Cattoir, H. & Reynaerts, A. (1970). The quantitative measurement of DNA hybridization from renaturation rates. Eur J Biochem 12, 143–153.[Medline]

Dong, X., Cheng, G. & Stams, A. J. M. (1994). Butyrate oxidation by Syntrophospora bryantii in coculture with different methanogens and in pure culture with pentenoate as electron acceptor. Appl Microbiol Biotechnol 42, 647–652.[CrossRef]

Felsenstein, J. (1993). PHYLIP (phylogeny inference package), version 3.5c. Department of Genetics, University of Washington, Seattle, USA.

Hungate, R. E. (1969). A roll-tube method for cultivation of strict anaerobes. Methods Microbiol 3B, 117–132.

Marmur, J. (1961). A procedure for the isolation of deoxyribonucleic acid from microorganisms. J Mol Biol 3, 208–218.

Marmur, J. & Doty, P. (1962). Determination of the base composition of deoxyribonucleic acid from its thermal denaturation temperature. J Mol Biol 4, 109–118.

McInerney, M. J., Bryant, M. P. & Pfennig, N. (1979). Anaerobic bacterium that degrades fatty acids in syntrophic association with methanogens. Arch Microbiol 122, 129–135.[CrossRef]

Rainey, F. A. & Stackebrandt, E. (1993). 16S rDNA analysis reveals phylogenetic diversity among the polysaccharolytic clostridia. FEMS Microbiol Lett 113, 125–128.[CrossRef][Medline]

Rainey, F. A., Ward-Rainey, N. L., Janssen, P. H., Hippe, H. & Stackebrandt, E. (1996). Clostridium paradoxum DSM 7308T contains multiple 16S rRNA genes with heterogeneous intervening sequences. Microbiology 142, 2087–2095.[Abstract/Free Full Text]

Schink, B. (1992). Syntrophism among prokaryotes. In The Prokaryotes, 2nd edn, pp. 276–299. Edited by A. Balows, H. G. Trüper, M. Dworkin, W. Harder & K.-H. Schleifer. New York: Springer Verlag.

Schink, B. (1997). Energetics of syntrophic cooperation in methanogenic degradation. Microbiol Mol Biol Rev 61, 262–280.[Abstract]

Stackebrandt, E., Kramer, I., Swiderski, J. & Hippe, H. (1999). Phylogenetic basis for a taxonomic dissection of the genus Clostridium. FEMS Immunol Med Microbiol 24, 253–258.[CrossRef][Medline]

Stams, A. J. M. (1994). Metabolic interactions between anaerobic bacteria in methanogenic environments. Antonie van Leeuwenhoek 66, 271–294.[CrossRef][Medline]

Staneck, J. L. & Roberts, G. D. (1974). Simplified approach to identification of aerobic actinomycetes by thin-layer chromatography. Appl Microbiol 28, 226–231.[Medline]

Takai, K., Moser, D. P., Onstott, T. C., Spoelstra, N., Pfiffner, S. M., Dohnalkova, A. & Fredrickson, J. K. (2001). Alkaliphilus transvaalensis gen. nov., sp. nov., an extremely alkaliphilic bacterium isolated from a deep South African gold mine. Int J Syst Evol Microbiol 51, 1245–1256.[Abstract]

Wayne, L. G., Brenner, D. J., Colwell, R. R. & 9 other authors (1987). International Committee on Systematic Bacteriology. Report of the ad hoc committee on reconciliation of approaches to bacterial systematics. Int J Syst Bacteriol 37, 463–464.[Free Full Text]

Winker, S. & Woese, C. R. (1991). A definition of the domains Archaea, Bacteria and Eucarya in terms of small subunit ribosomal RNA characteristics. Syst Appl Microbiol 14, 305–310.[Medline]

Wofford, N. Q., Beaty, P. S. & McInerney, M. J. (1986). Preparation of cell-free extracts and the enzymes involved in fatty acid metabolism in Syntrophomonas wolfei. J Bacteriol 167, 179–185.[Abstract/Free Full Text]

Zhao, H. X., Yang, D. C., Woese, C. R. & Bryant, M. P. (1990). Assignment of Clostridium bryantii to Syntrophospora bryantii gen. nov., comb. nov. on the basis of a 16S rRNA sequence analysis of its crotonate-grown pure culture. Int J Syst Bacteriol 40, 40–44.[Abstract/Free Full Text]




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