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Departament de Microbiologia i Parasitologia Sanitàries, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain
Correspondence
J. Gaspar Lorén
jgloren{at}ub.edu
| ABSTRACT |
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Published online ahead of print on 15 June 2004 as DOI 10.1099/ijs.0.63202-0.
The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains 93M, 431E, 848TT, 849T and 869N are AY532688AY532692, respectively.
A dendrogram of AFLP profiles and tables showing 16S rRNA gene sequence similarities and DNADNA hybridization data are available as supplementary material in IJSEM Online.
| MAIN TEXT |
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-Proteobacteria. Aeromonads are autochthonous to aquatic environments worldwide and are usual microbiota (as well as primary or secondary pathogens) of fish, amphibians and other animals. Some motile species (mainly Aeromonas caviae, Aeromonas hydrophila and Aeromonas veronii bv. Sobria) are opportunistic pathogens of humans (Janda & Abbott, 1998
The taxonomy of the genus Aeromonas appears to change continually, due to the addition of newly described species and the reclassification or extended description of existing taxa. Since the first DNADNA hybridization study that was performed on Aeromonas (Popoff et al., 1981
) and the description of the genus with four phenospecies (A. caviae, A. hydrophila, Aeromonas salmonicida and A. sobria) in Bergey's Manual of Systematic Bacteriology (Popoff, 1984
), 18 Aeromonas species have been described: A. hydrophila, Aeromonas bestiarum, A. salmonicida, A. caviae, Aeromonas media, Aeromonas eucrenophila, Aeromonas sobria, Aeromonas jandaei, A. veronii, Aeromonas sp. HG11, Aeromonas schubertii, Aeromonas sp. HG13 (enteric Group 501), Aeromonas trota, Aeromonas allosaccharophila, Aeromonas encheleia, Aeromonas popoffii, Aeromonas culicicola and the most recently described species, Aeromonas simiae (Huys et al., 2002
; Pidiyar et al., 2002
; Esteve et al., 2003
; Harf-Monteil et al., 2004
).
The present investigation was initiated to determine the taxonomic position of a group of five strains that were isolated from bivalve molluscs, which clustered together as a separate phenon (phenon VI) in a previous phenotypic study (Miñana-Galbis et al., 2002
). We have completed the phenotypic study and subjected this group of strains to amplified fragment length polymorphism (AFLP) analysis, 16S rRNA gene sequencing, DNA G+C content determination and DNADNA homology determination. In this genotypic study, we included the reference strains of the Aeromonas DNA hybridization groups (HGs) that are currently described. The data indicated that our strains are genotypically and phenotypically distinct from the Aeromonas species that have been accepted until now and that they constitute a homogeneous taxon, for which the name Aeromonas molluscorum sp. nov. is proposed.
The five strains 848TT (=CECT 5864T=LMG 22214T), 93M (=CECT 5865=LMG 22215), 431E (=CECT 5866=LMG 22216), 849T (=CECT 5867=LMG 22217) and 869N (=CECT 5868=LMG 22218) were isolated from wedge-shells (Donax trunculus), mussels (Mytilus sp.), cockles (Cardium sp.), wedge-shells (Donax trunculus) and razor-shells (Ensis sp.), respectively, from various retail markets in Barcelona (Spain) between April and October 1997. Bivalves without their shells (25 g) were suspended 1/10 (w/v) in 1/4 Ringer's solution for homogenization in a Masticator (IUL Instruments). Samples and serial dilutions were cultured on m-Aeromonas selective agar base Havelaar (Biolife) and the same medium with 10 mg ampicillin l1 for 2448 h at 25 °C. Samples were also enriched in tryptone soy broth (TSB) and alkaline peptone water (pH 9·0) overnight and then inoculated on the above-mentioned media. Isolates were grown on tryptone soy agar (TSA) for purification and further study. Strains were maintained in TSB with 20 % (v/v) glycerol at 40 °C.
Cell size, morphology and flagellar arrangement were determined by transmission electron microscopy (JEOL 1010). Cells were grown on TSA supplemented with 0·5 % (w/v) NaCl for 48 h at 25 °C and, after further suspension in MilliQ water, were examined by negative staining with 2 % (w/v) uranyl acetate.
Physiological and biochemical characterization, unless otherwise stated, was performed at 25 °C and all media contained 1 % (w/v) NaCl (Miñana-Galbis et al., 2002
). Gram-staining, motility, glucose oxidationfermentation test, oxidase and catalase activity, nitrate reduction, indole production, susceptibility to vibriostatic agent O/129, swarming motility, production of a brown diffusible pigment, gas production from D-glucose, methyl red (MR) and VogesProskauer (VP) reactions,
-galactosidase activity (ONPG), hydrogen sulfide production from cysteine and thiosulfate, growth on MacConkey agar, salt tolerance, pH and temperature ranges for growth, acid production from carbohydrates, hydrolysis of arbutin, DNA, elastin, aesculin, starch, urea and xanthine, utilization of substrates as sole carbon and energy sources and sensitivity to antibiotics were determined as described previously (Miñana-Galbis et al., 2002
). Arginine dehydrolase (ADH), lysine decarboxylase (LDC) and ornithine decarboxylase (ODC) activity (Moeller's method) and gelatin hydrolysis by using tannic acid (1 %) as the gelatin-precipitating reagent were determined as described by Smibert & Krieg (1994)
.
For 16S rRNA gene sequencing and phylogenetic analysis, DNA was extracted by using a REALPURE genomic DNA extraction kit (RBMEG03; Durviz). Oligonucleotide primers used for PCR amplification and sequencing of the 16S rRNA gene were those described by Martínez-Murcia et al. (1999)
. DNA was subjected to PCR amplification in a total volume of 50 µl that contained 50 mM KCl, 15 mM Tris/HCl (pH 8·0), 1·5 mM MgCl2, 0·2 mM each deoxyribonucleotide (dATP, dCTP, dGTP, dTTP; Amersham Biosciences), 1·25 U AmpliTaq Gold DNA polymerase (Applera) and 25 pmol each primer. The reaction mixtures were subjected to the following thermal cycling: an initial single step of 95 °C for 9 min, 30 cycles of 94 °C for 60 s, 51 °C for 30 s and 72 °C for 90 s, and a final single step of 72 °C for 10 min. PCR products were purified by using Montage PCR centrifugal filter devices (Millipore) and prepared for sequencing by employing a BigDye Terminator v3.1 cycle sequencing kit (Applera). The amplified 16S rRNA genes were sequenced with an ABI PRISM 3730 DNA analyser by the Scientific and Technical Services of Barcelona University.
The sequences obtained were aligned with 16S rRNA gene sequences of the type strains of all members of the genus Aeromonas that were available in GenBank by using the CLUSTAL_X program version 1.8 (Thompson et al., 1997
). Distances and clustering with the neighbour-joining and maximum-parsimony methods (pairwise deletion and Kimura two-parameter model) were determined by using the MEGA program version 2.1 (Kumar et al., 2001
). Stability of the relationships was assessed by bootstrapping (1000 replicates).
AFLP analysis, which included DNA extraction and purification (Pitcher et al., 1989
), AFLP fingerprinting, data processing and numerical analysis (Huys & Swings, 1999
), was performed by the BCCM/LMG (Belgian Coordinated Collections of Microorganisms/Laboratorium voor Microbiologie from Universiteit Gent) Identification Service.
For DNADNA hybridization and determination of DNA G+C content, genomic DNA of bacterial strains was prepared according to a modification of the procedure of Wilson (1987)
. The G+C content of each DNA sample was determined by three independent analyses using the HPLC technique (Mesbah et al., 1989
). DNADNA hybridizations were performed in four replicates at 47 °C according to a modification of the method described by Ezaki et al. (1989)
. These analyses were performed by the BCCM/LMG Identification Service.
The five strains isolated from bivalve molluscs (848TT, 93M, 431E, 849T and 869N) were identified as belonging to the genus Aeromonas as they were Gram-negative, rod-shaped, motile by one polar flagellum, oxidase-positive, facultatively anaerobic, glucose-fermentative and resistant to vibriostatic agent O/129 and could grow in the absence of NaCl, but not at 6 % (w/v) NaCl. Cells of all isolates were about 1·22·2x0·51·0 µm in size. Their antibiotic-resistance pattern was similar to that of all Aeromonas species (Kämpfer et al., 1999
). These strains formed non-pigmented, circular colonies with a diameter of 34 mm on TSA when incubated at 25 °C. The growth-temperature range was 437 °C and optimal growth occurred at 2530 °C.
The novel mesophilic species showed several differentiating phenotypic features in relation to other mesophilic Aeromonas species (Table 1
). Four or more tests allowed differentiation of A. molluscorum from all Aeromonas species except A. caviae, A. media and A. simiae. Negative reactions in the tests for indole production and starch hydrolysis allowed the separation of A. molluscorum from A. caviae. Brown pigment production and the above-mentioned tests discriminated A. molluscorum from A. media. A. molluscorum could be differentiated from A. simiae by lysine decarboxylation and acid production from L-arabinose and D-mannitol. These results allowed the phenotypic discrimination of A. molluscorum from all Aeromonas taxa that have been described to date.
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The DNA G+C content of strains 93M, 431E, 848TT, 849T and 869N was 59·059·4 mol%, which agrees with the range described for the genus Aeromonas (5763 mol%; Holt et al., 1994
). Results of DNADNA hybridization experiments are summarized in Supplementary Table B in IJSEM Online. We chose two representative isolates from the novel Aeromonas species, the type strain (848TT) and strain 93M. These two strains showed 93 % DNADNA similarity, clearly above the level of 70 % that is accepted as the limit for species delineation (Wayne et al., 1987
). The type strain of A. molluscorum clearly showed <70 % DNADNA similarity (2745 %) with any of the type/reference strains of the current Aeromonas HGs. Therefore, A. molluscorum constitutes a new Aeromonas HG.
Based on the results of DNADNA hybridization, phenotypic characterization, AFLP analysis and 16S rRNA gene sequencing, we propose that strains 93M, 431E, 848TT, 849T and 869N represent a novel species within the genus Aeromonas, for which we propose the name Aeromonas molluscorum sp. nov.
Description of Aeromonas molluscorum sp. nov.
Aeromonas molluscorum (mol.lus.co'rum. N.L. pl. n. Mollusca a zoological phylum; N.L. gen. pl. n. molluscorum of molluscs classified in the phylum Mollusca).
Cells are Gram-negative, straight, motile rods with a polar flagellum, 1·22·2 µm long and 0·51·0 µm wide. Colonies on TSA are 34 mm in diameter, translucent to opaque, circular and beige in colour after 48 h at 25 °C. Growth occurs at 437 °C, but not at 40·5 °C; optimal growth occurs at 2530 °C. Oxidase- and catalase-positive, reduces nitrate to nitrite and is resistant to vibriostatic agent O/129 (150 µg). Indole, brown diffusible pigment, swarming, gas from D-glucose and hydrogen sulfide from cysteine and thiosulfate are not produced. Positive for glucose oxidationfermentation, ADH, MR and ONPG tests. Negative for VP, LDC and ODC tests. Grows on MacConkey agar. Able to grow at 03 % NaCl and pH 9·0, but not at 6 % NaCl or pH 4·5. All strains hydrolyse arbutin, DNA, aesculin and gelatin, but not starch, elastin, urea or xanthine. All strains produce acid from L-arabinose, arbutin (except strain 93M), D-cellobiose (except strain 431E), dextrin, D-galactose, glycerol, D-mannitol, D-mannose, D-sucrose and D-trehalose, but not from lactose, D-melibiose, D-raffinose, L-rhamnose, sorbitol or D-xylose. The following substrates are used as sole carbon and energy sources: acetate (except strain 93M), L-arabinose, arbutin, L-arginine, D-cellobiose (except strain 431E), citrate, aesculin, D-fructose, D-galactose, D-glucose, glycerol, L-histidine, maltose, D-mannitol, D-mannose, N-acetylglucosamine, D-sucrose, salicin (except strain 93M) and D-trehalose. None of the strains uses adonitol, dulcitol, inositol, inulin, lactose, D-melezitose, D-melibiose, D-raffinose, L-rhamnose, sorbitol, L-sorbose or D-xylose. All strains are resistant to ampicillin (10 µg) (except strain 431E), erythromycin (15 µg) and penicillin G (10 µg). All strains show intermediate sensitivity to streptomycin (10 µg) and are sensitive to amikacin (30 µg), amoxycillin+clavulanic acid (30 µg) (intermediate sensitivity for strains 93M and 869N), cefoxitin (30 µg) (except strain 93M), ceftriaxon (30 µg), cefuroxime (30 µg), cephalothin (30 µg) (except strains 93M and 869N), ciprofloxacin (5 µg), colistin (50 µg), gentamicin (10 µg), imipenem (10 µg), polymyxin B (300 U), tetracycline (30 µg), tobramycin (10 µg) and trimethoprim+sulfamethoxazole (1·25 µg+23·75 µg). DNA G+C content is 59·059·4 mol%.
The type strain, 848TT (=CECT 5864T=LMG 22214T), was isolated from wedge-shells (Donax trunculus) obtained from a retail market in Barcelona (Spain) in 1997.
| ACKNOWLEDGEMENTS |
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| REFERENCES |
|---|
|
|
|---|
Carson, J., Wagner, T., Wilson, T. & Donachie, L. (2001). Miniaturized tests for computer-assisted identification of motile Aeromonas species with an improved probability matrix. J Appl Microbiol 90, 190200.[CrossRef][Medline]
Esteve, C., Valera, L., Gutiérrez, C. & Ventosa, A. (2003). Taxonomic study of sucrose-positive Aeromonas jandaei-like isolates from faeces, water and eels: emendation of A. jandaei Carnahan et al. 1992. Int J Syst Evol Microbiol 53, 14111419.
Euzéby, J. P. (1998). Necessary corrections according to Judicial Opinions 16, 48 and 52. Int J Syst Bacteriol 48, 613.
Ezaki, T., Hashimoto, Y. & Yabuuchi, E. (1989). Fluorometric deoxyribonucleic acid-deoxyribonucleic acid hybridization in microdilution wells as an alternative to membrane filter hybridization in which radioisotopes are used to determine genetic relatedness among bacterial strains. Int J Syst Bacteriol 39, 224229.
Harf-Monteil, C., Le Flèche, A., Riegel, P., Prévost, G., Bermond, D., Grimont, P. A. D. & Monteil, H. (2004). Aeromonas simiae sp. nov., isolated from monkey faeces. Int J Syst Evol Microbiol 54, 481485.
Holt, J. C., Krieg, N. R., Sneath, P. H. A., Stanley, J. Y. & Williams, S. T. (1994). Subgroup 2: family Vibrionaceae. In Bergey's Manual of Determinative Bacteriology, 9th edn, pp. 190274. Baltimore: Lippincott Williams & Wilkins.
Huys, G. & Swings, J. (1999). Evaluation of a fluorescent amplified fragment length polymorphism (FAFLP) methodology for the genotypic discrimination of Aeromonas taxa. FEMS Microbiol Lett 177, 8392.[CrossRef]
Huys, G., Kämpfer, P., Altwegg, M. & 7 other authors (1997). Aeromonas popoffii sp. nov., a mesophilic bacterium isolated from drinking water production plants and reservoirs. Int J Syst Bacteriol 47, 11651171.
Huys, G., Kämpfer, P., Albert, M. J., Kühn, I., Denys, R. & Swings, J. (2002). Aeromonas hydrophila subsp. dhakensis subsp. nov., isolated from children with diarrhoea in Bangladesh, and extended description of Aeromonas hydrophila subsp. hydrophila (Chester 1901) Stanier 1943 (Approved Lists 1980). Int J Syst Evol Microbiol 52, 705712.[Abstract]
Huys, G., Pearson, M., Kämpfer, P., Denys, R., Cnockaert, M., Inglis, V. & Swings, J. (2003). Aeromonas hydrophila subsp. ranae subsp. nov., isolated from septicaemic farmed frogs in Thailand. Int J Syst Evol Microbiol 53, 885891.
Janda, J. M. & Abbott, S. L. (1998). Evolving concepts regarding the genus Aeromonas: an expanding panorama of species, disease presentations, and unanswered questions. Clin Infect Dis 27, 332344.[Medline]
Kämpfer, P., Christmann, C., Swings, J. & Huys, G. (1999). In vitro susceptibilities of Aeromonas genomic species to 69 antimicrobial agents. Syst Appl Microbiol 22, 662669.[Medline]
Kumar, S., Tamura, K., Jakobsen, I. B. & Nei, M. (2001). MEGA2: molecular evolutionary genetic analysis software. Bioinformatics 17, 12441245.
Martínez-Murcia, A. J. (1999). Phylogenetic positions of Aeromonas encheleia, Aeromonas popoffii, Aeromonas DNA hybridization Group 11 and Aeromonas Group 501. Int J Syst Bacteriol 49, 14031408.
Martínez-Murcia, A. J., Antón, A. I. & Rodríguez-Valera, F. (1999). Patterns of sequence variation in two regions of the 16S rRNA multigene family of Escherichia coli. Int J Syst Bacteriol 49, 601610.
Mesbah, M., Premachandran, U. & Whitman, W. B. (1989). Precise measurement of the G+C content of deoxyribonucleic acid by high-performance liquid chromatography. Int J Syst Bacteriol 39, 159167.
Miñana-Galbis, D., Farfán, M., Lorén, J. G. & Fusté, M. C. (2002). Biochemical identification and numerical taxonomy of Aeromonas spp. isolated from environmental and clinical samples in Spain. J Appl Microbiol 93, 420430.[CrossRef][Medline]
Pidiyar, V., Kaznowski, A., Narayan, N. B., Patole, M. & Shouche, Y. S. (2002). Aeromonas culicicola sp. nov., from the midgut of Culex quinquefasciatus. Int J Syst Evol Microbiol 52, 17231728.[Abstract]
Pitcher, D. G., Saunders, N. A. & Owen, R. J. (1989). Rapid extraction of bacterial genomic DNA with guanidium thiocyanate. Lett Appl Microbiol 8, 151156.
Popoff, M. (1984). Genus III. Aeromonas. In Bergey's Manual of Systematic Bacteriology, pp. 545548. Edited by N. R. Krieg & J. G. Holt. Baltimore: Williams & Wilkins.
Popoff, M. Y., Coynault, C., Kiredjian, M. & Lemelin, M. (1981). Polynucleotide sequence relatedness among motile Aeromonas species. Curr Microbiol 5, 109114.
Smibert, R. M. & Krieg, N. R. (1994). Phenotypic characterization. In Methods for General and Molecular Bacteriology, pp. 607655. Edited by P. Gerhardt, R. G. E. Murray, W. A. Wood & N. R. Krieg. Washington, DC: American Society for Microbiology.
Stackebrandt, E. & Goebel, B. M. (1994). Taxonomic note: a place for DNA-DNA reassociation and 16S rRNA sequence analysis in the present species definition in bacteriology. Int J Syst Bacteriol 44, 846849.
Thompson, J. D., Gibson, T. J., Plewniak, F., Jeanmougin, F. & Higgins, D. G. (1997). The CLUSTAL_X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Res 25, 48764882.
Valera, L. & Esteve, C. (2002). Phenotypic study by numerical taxonomy of strains belonging to the genus Aeromonas. J Appl Microbiol 93, 7795.[CrossRef][Medline]
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, 463464.
Wilson, K. (1987). Preparation of genomic DNA from bacteria. In Current Protocols in Molecular Biology, pp. 2.4.1.2.4.5. Edited by F. M. Ausubel, R. Brent, R. E. Kingston, D. D. Moore, J. G. Seidman, J. A. Smith & K. Struhl. New York: Greene Publishing and Wiley Interscience.
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