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Institut National de la Recherche Agronomique, Unité d'Ecologie Microbienne des Insectes et Interactions hôte-Pathogène, Université Montpellier II, Place Eugène Bataillon, Case courrier 54, Bâtiment 24, 34095 Montpellier CEDEX 5, France
Correspondence
Patrick Tailliez
tailliez{at}univ-montp2.fr
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. The bacteria of this genus are symbiotically associated with insect-pathogenic nematodes of the genus Steinernema (Travassos, 1927). This genus currently comprises Xenorhabdus nematophila Thomas and Poinar 1979 (the type species), three further species described by Akhurst & Boemare (1988) (Xenorhabdus beddingii, X. bovienii and X. poinarii), Xenorhabdus japonica described by Nishimura et al. (1994), four species described recently by Lengyel et al. (2005) (Xenorhabdus budapestensis, X. ehlersii, X. innexi, X. szentirmaii) and ‘Xenorhabdus indica’, described by Somvanshi et al. (2006) but not yet validly published. Our collection comprised 76 Xenorhabdus strains isolated from at least 27 Steinernema species collected in 32 countries. The strains were characterized by molecular and phenotypic approaches. The phylogenetic spectrum of these Xenorhabdus strains was found to be broad, including many novel species dispersed among type strains in the 16S rRNA gene phylogenetic tree.
Bacterial strains and culture conditions
The bacterial strains studied were part of our collection (31 strains) (Université Montpellier II, France) or were provided by the DSMZ collection (six strains) (http://www.dsmz.de) (Table 1). Thirty-nine new isolates were obtained from the infective stages of nematodes of the genus Steinernema (Table 1) by the hanging-drop technique (Poinar, 1966). Bacteriological purity was checked by plating on nutrient agar supplemented with 0.004 % (w/v) triphenyltetrazolium chloride and 0.0025 % (w/v) bromothymol blue (NBTA medium) at 28 °C (Akhurst, 1980). The isolates were examined for the main phenotypic characteristics of the genus Xenorhabdus, using the methods of Boemare & Akhurst (1988). Strains were stored at –80 °C in LB broth (Difco) containing 15 % glycerol (v/v).
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. Phenotypic tests on agar plates (ampicillin susceptibility, dye adsorption, colony pigmentation, antibiosis, cultures in Tween media, gelatin hydrolysis, DNase and lecithinase activities, haemolysis) have been described elsewhere (Akhurst, 1980; Boemare & Akhurst, 1988; Akhurst et al., 1996). Phenotypic data were analysed with BioNumerics software (Applied Maths). Five similarity matrices were calculated using only variable characters, each corresponding to a set of data: growth at different temperatures (11 variable characters), enzyme activities (n=10), carbon source assimilation (n=69), carbon source fermentation (n=45) and phenotypic tests on agar plates (n=18). Weakly positive results were scored as 0.5 and the data were compared using the Gower similarity coefficient (Gower & Legendre, 1986). The five similarity matrices were combined such that each set of data contributed equally to the combined similarity matrix, regardless of the number of characters it contained. The resulting dendrogram was calculated by the unweighted pair group method using arithmetic means (UPGMA) (Sokal & Michener, 1958).
Molecular characterization of bacterial strains and data analysis
Total bacterial genomic DNA was extracted with the QIAamp DNA mini kit (Qiagen). The almost-complete 16S rRNA gene was amplified by PCR using primers 16SP1 (5'-GAAGAGTTTGATCATGGCTC-3', corresponding to Escherichia coli 16S rRNA positions 6–25, forward) and 16SP2 (5'-AAGGAGGTGATCCAGCCGCA-3', corresponding to positions 1522–1540, reverse). PCR was carried out in a final volume of 50 µl containing 20–100 ng DNA, 3 mM MgCl2 (Invitrogen), 0.1 mM of each primer, 200 µM of each dNTP (Invitrogen) and 2.5 U Taq DNA polymerase (Invitrogen) in the buffer supplied with the enzyme. Amplification conditions were: 94 °C for 2 min followed by 35 cycles of 30 s at 95 °C, 30 s at 63 °C and 1 min at 72 °C, followed by 7 min at 72 °C. PCR products were purified using a Montage PCR device (Millipore). Sequences overlapping the 16S rRNA gene were then obtained using three sequencing primers (SP1, 5'-ACCGCGGCTGCTGGCACG-3', position 514 reverse; SP2, 5'-CTCGTTGCGGGACTTAAC-3', position 1089 reverse; and 16SP2) and merged using SeqMan II (DNAStar). Multiple alignments of the 16S rRNA gene sequences were obtained with CLUSTAL W (http://clustalw.genome.jp/) and the distance tree was calculated using the model of Jukes & Cantor (1969) and the neighbour-joining (NJ) method (Saitou & Nei, 1987) included in PAUP software (Swofford, 2003). Bootstrap analysis was carried out with 1000 datasets. We also used the maximum-likelihood (ML) and parsimony methods included in PAUP to compare the topologies of the phylogenetic trees obtained for a given set of sequences.
The 16S rRNA gene restriction fragment length polymorphism (RFLP) typing method was carried out as described previously (Fischer-Le Saux et al., 1998). The RFLP data are not presented here, but were used to select representative strains of X. bovienii (11/25), X. nematophila (6/13) and X. poinarii (4/5) from the strains of our collection for which 16S rRNA gene sequences have been determined. Randomly amplified polymorphic DNA (RAPD) profiles (Williams et al., 1990) were determined using primers P1 (5'-TGCTCTGCCC-3'), P2 (5'-GGTGACGCAG-3') and P3 (5'-TCGCTGGGAC-3') in separate reactions. Enterobacterial repetitive intergenic consensus (ERIC) (Hulton et al., 1991) PCR profiles were determined using the primers ERIC1R (5'-GCTATGCTCCYGGGGRTT-3') and ERIC2 (5'-ACTATGTGAYTGGGGTGA-3'). The sequences of the ERIC primers proposed by Versalovic et al. (1991) were modified to correspond to the ERIC sequences present in the Xenorhabdus genome (http://maizeapache.ddpsc.org/xeno_blast/index.html). PCR amplifications were performed in a final volume of 50 µl containing 1x PCR buffer (Qbiogene), 20–100 ng bacterial genomic DNA, 0.2 mM MgCl2, 0.5 µM primer, 200 µM of each dNTP and 3.75 U Taq DNA polymerase (concentration of enzyme stock 15 U µl–1). PCR was carried out in a GeneAmp 2400 thermal cycler PCR system (Perkin Elmer) programmed for 30 cycles of amplification of 1 min at 94 °C, 1 min at 48 °C (ERIC) or 42 °C (RAPD), 3 min (ERIC) to 6 min (RAPD) of temperature ramping to 72 °C and 1 min at 72 °C, after an initial 5 min denaturation at 94 °C. Electrophoresis was carried out as described previously (Tailliez et al., 1998). Molecular typing profiles were acquired with a CCD camera (Sony) and photocapture software (PHOTO-CAPT; Fisher Bioblock Scientific). For each strain, the ERIC profile and the three RAPD profiles were combined and then compared using Pearson's similarity coefficient. The resulting dendrogram was calculated with the UPGMA module of the GelCompar software (Applied-Maths).
Comparison of 16S rRNA gene sequences
Fig. 1 shows the distance tree resulting from comparison of the 16S rRNA gene sequences of 54 representative Xenorhabdus strains selected from the 76 strains studied (Table 1). Representative strains were selected from the species X. nematophila, X. bovienii and X. poinarii, taking into account geographical origin, species of nematode host and the diversity of 16S rRNA gene RFLP profiles. The 16S rRNA gene sequence obtained from strain IAM 14265T, which should correspond to X. japonica SK-1T, was actually similar to that of X. nematophila strains and therefore significantly different from the sequence of X. japonica SK-1T deposited in GenBank under accession number D78008. Our result was confirmed by the staff of the IAM collection. We therefore used the X. japonica type strain deposited in the DSMZ under accession number DSM 16522T instead. This strain has a 16S rRNA gene sequence (GenBank accession number DQ202310) very similar to the GenBank sequence of X. japonica SK-1T.
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; Moran et al., 1993), the common ancestor of the genus Xenorhabdus probably emerged between 250 and 500 million years ago. These data are consistent with Poinar's speculations that nematodes of the genus Steinernema probably emerged about 375 million years ago (Poinar, 1993). On the bacterial evolution time scale, we can consider the genus Xenorhabdus to have emerged relatively recently. Forty-seven sequences were distributed between 13 groups, G1 to G13, based on high bootstrap values (>98 %) in the distance tree. Seven sequences, corresponding to strains TH01T, ID10T, USNJ01T, VC01T, Q1T, PR06-AT and X. beddingii DSM 4764T, were not included in these groups. The composition of the 13 groups of sequences was confirmed using the ML and parsimony methods of phylogenetic tree reconstruction and using the 16S rRNA gene sequences of Photorhabdus luminescens subsp. laumondii TT01T (GenBank accession no. AJ007404), Proteus vulgaris CIP 103181T (AJ301683) and E. coli ATCC 11775T (X80725) as outgroups (data not shown). Although the bootstrap values at the nodes between groups G1 to G4 were less than 50 %, these four groups were linked similarly by the ML and parsimony methods, suggesting that they were phylogenetically related. Similarly, the sequence of strain ID10T was linked to those of group G5 and the sequence of strain PR06-AT was linked to those of group G11 in all three methods of phylogenetic tree reconstruction. The sequences of strains TH01T, USNJ01T, VC01T and Q1T and the X. beddingii type strain DSM 4764T were not robustly linked to any of the 13 groups of sequences defined in this work. Moreover, relationships between the groups, with the exception of relationships between G1, G2, G3 and G4 (see above), appeared to be unreliable, suggesting (i) that the 16S rRNA gene sequences used were insufficiently informative for phylogenetic analysis and/or (ii) an explosive radiation of diversity within the genus Xenorhabdus.
Comparison of molecular typing profiles
The differences between two Xenorhabdus 16S rRNA gene sequences were often less than 3 % (and always less than 5 %), so this frequently used bacterial taxonomy threshold (Stackebrandt & Goebel, 1994) cannot be used here to support proposals for novel species of Xenorhabdus. This observation was also true for the genus Photorhabdus of nematode-symbiotic bacteria (Akhurst et al., 2004). Quantitative DNA–DNA hybridization data were available only for representative strains of five species with validly published names, X. nematophila, X. bovienii, X. poinarii, X. beddingii and X. japonica (Boemare et al., 1993; Nishimura et al., 1994), and for strains K77, SaVT and Q1T (Boemare et al., 1993). We therefore assessed the relationships between our strains using a combination of molecular typing techniques (ERIC and RAPD fingerprinting) that could be performed easily for such a large collection of bacteria. These molecular typing methods are based on the amplification of conserved and variable regions of the genome. They enabled us to group together strains belonging to the same species based on the amplification of conserved genomic regions (migration of bands of the same size in different profiles). This approach was used successfully for Campylobacter and its relatives (Mazurier et al., 1992), for which phenotypic inertness has prevented the development of a phenotypic identification scheme (Vandamme et al., 1996), and for some closely related species of lactobacilli showing an overall phenotypic similarity (e.g. the Lactobacillus acidophilus group) (Gancheva et al., 1999). Similarly, the combined use of RAPD and ERIC fingerprinting was used successfully to differentiate Salmonella species (Lim et al., 2005).
A comparison of the molecular typing profiles of the 76 Xenorhabdus strains studied (Fig. 2) led to the identification of groups corresponding to those defined by 16S rRNA gene sequences analysis, except for group G6, in which strain VN01 and X. japonica DSM 16522T displayed very different molecular typing profiles (Pearson similarity coefficient of 10 %), and for group G8, in which strain TB20 displayed a unique molecular typing profile. Within group G8, strains TB01, TB10 and TB30, all of which originated from China, clustered together and strains CA04 and USNY95, both isolated from Steinernema kraussei, and strain Si, isolated from Steinernema intermedium, were distinguished on the basis of their molecular typing profiles. In addition, the DNA–DNA relatedness between X. bovienii T228T (associated with Steinernema feltiae) and strain Si (associated with S. intermedium) was only 64 %, whereas the DNA relatedness between the X. bovienii type strain T228T and strains F3 and SK2 (associated with Steinernema affine and S. kraussei, respectively) was 75 % (Boemare et al., 1993). Within group G9, X. poinarii strain CU01, isolated from Steinernema cubanum, was distinguished from the four X. poinarii strains isolated from Steinernema glaseri. Similarly, the DNA–DNA relatedness between X. poinarii G6T (associated with S. glaseri) and strain CU01 (associated with S. cubanum) was only 68 %, with a 
Tm value of 3 °C, whereas the DNA–DNA relatedness between X. poinarii G6T and strain NC33 (associated with S. glaseri) was 96 %, with a Tm value of 2.4 °C (Fischer-Le Saux et al., 1999a). These results obtained using the DNA–DNA hybridization technique and our molecular typing method indicated the particular position of strains Si and CU01 within X. bovienii and X. poinarii, respectively. Strains TH01T, ID10T, VC01T, PR06-AT, USNJ01T, Q1T and X. beddingii DSM 4764T, the 16S rRNA gene sequences of which were not included in any group, displayed unique molecular typing profiles.
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; Fischer-Le Saux et al., 1999a; Nishimura et al., 1994), thus indicating that our molecular typing technique has a level of resolution comparable to that of DNA–DNA hybridization. In addition, the groupings substantiate those obtained from analysis of 16S rRNA gene sequences. These results suggest that our approach is a reliable alternative to the quantitative DNA–DNA hybridization method generally used in bacterial taxonomy in cases in which a large number of bacterial strains with very similar 16S rRNA gene sequences are studied. Based on this approach, we were able (i) to classify 32 new isolates to the previously described Xenorhabdus species, adding new members to recently described species previously represented by the type strain only (Lengyel et al., 2005; Somvanshi et al., 2006), (ii) to confirm the validity of the five species proposed by Lengyel et al. (2005) and Somvanshi et al. (2006), despite the absence of quantitative DNA–DNA hybridization data and the high level of similarity of their 16S rRNA gene sequences (e.g. X. budapestensis–X. ehlersii, 98 %; X. szentirmaii–X. nematophila, 97.5 %), (iii) to propose the description of ten novel Xenorhabdus species (see below) and (iv) to assign 16 strains to these novel Xenorhabdus species, with isolates VN01 and TB20 remaining unclassified.
Comparison of phenotypic patterns
All the strains displayed the phenotypic characters of form I described previously for the genus Xenorhabdus (Akhurst & Boemare, 2005) with the exception of X. ehlersii DSM 16337T and X. japonica DSM 16522T, provided by the DSMZ, which contained form II only. All strains except X. bovienii BE05, X. ehlersii DSM 16337T and X. japonica DSM 16522T produced antibiotics and none of the strains displayed any of the following characters: bioluminescence, oxidase, catalase, urease or nitrate reductase activity, Voges–Proskauer reaction, ONPG (o-nitrophenol 
-D-galactopyranoside) and H2S production. Table 2 summarizes the most significant phenotypic features of the strains of the previously described Xenorhabdus species and of the ten novel Xenorhabdus species proposed here.
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). Similarity coefficients exceeded 70 %, suggesting that phenotypic analysis would be unlikely to lead to the identification of phenotypic features for reliable discrimination between Xenorhabdus species. A comparison of the phenotypic patterns led to the identification of two main phenotypic groups. Phenotypic group GA comprised strains able to grow at temperatures of 35–42 °C, whereas phenotypic group GB comprised strains growing at temperatures below 35 °C, suggesting that some Xenorhabdus species may have become adapted to tropical or temperate regions and/or influenced by the optimal growth and development temperature of their nematode host [e.g. the optimum temperatures for growth and development of Steinernema carpocapsae, S. monticolum, S. scarabaei and S. weiseri, associated with X. nematophila, Xenorhabdus hominickii sp. nov., Xenorhabdus koppenhoeferi sp. nov. and X. bovienii (group GB), respectively, ranged from 20 to 25 °C, whereas those of Steinernema riobrave and S. abbasi, associated with Xenorhabdus cabanillasii sp. nov. and ‘X. indica’ (group GA), respectively, ranged from 30 to 35 °C (Cabanillas et al., 1994; Elawad et al., 1997; Mrá
ek et al., 2003; Saunders & Webster, 1999; Stock & Koppenhöfer, 2003; Stock et al., 1997)]. The reliable phylogenetic relationships between strains of groups G1 to G4 (Fig. 1) were supported by the ability of the corresponding strains to grow at temperatures above 35 °C. Similarly, the phylogenetic relationships identified between strains ID10T and the ‘X. indica’ strains (group G5) and between strain PR06-AT and strains FRM16T and FRG31 (Xenorhabdus doucetiae sp. nov., group G11) were supported by the ability of these strains to grow at temperatures above 35 °C.
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) was generally consistent with the molecular classifications presented in Figs 1 and 2. The phenotypic patterns of the X. nematophila strains clustered together except for X. nematophila strain BE06, which was clustered with X. japonica DSM 16522T (phase II). The X. nematophila strains were characterized by an ability to grow only at temperatures below 35 °C, to produce acid from trehalose and to assimilate fructose and an inability to assimilate D-gluconate. Colonies were not pigmented. The phenotypic patterns of the X. bovienii strains also clustered together except for strains CA04 and USNY95. Similarly, strain TB20 displayed a unique phenotypic pattern. The X. bovienii strains were characterized mainly by their ability to grow only at temperatures below 33 °C and their ability to assimilate D-gluconate (Table 2). Strain VN01 and X. japonica DSM 16522T (group G6) had very different phenotypic patterns (Fig. 3; Table 2) and therefore could not be considered to belong to the same species on the basis of our phenotypic and molecular analysis alone. Strains KE01T, KR01 and KR05 (X. hominickii, group G7) clustered together based on phenotypic patterns, confirming that these strains belonged to the same species. The phenotypic patterns of the X. poinarii strains isolated from S. glaseri clustered together and were distinguished from the phenotypic pattern of X. poinarii CU01 isolated from S. cubanum. The X. poinarii strains were characterized mainly by their ability to grow at 40 °C, an absence of DNase and lecithinase activities and an inability to assimilate putrescine (Table 2). Strains JM26 and USTX62T (X. cabanillasii, group G13) clustered together on the basis of phenotypic patterns, confirming that they belonged to the same species. Thus, at least for these strains, phenotypic analysis confirmed the high reliability of our molecular classification of the Xenorhabdus strains.
For groups G4 and G12, the phenotypic patterns of the corresponding strains were not grouped together in hierarchical analysis (Fig. 3). However, for group G4 (Xenorhabdus kozodoii sp. nov.), composed of three strains originating from different countries (Italy, Russia, Spain), a combination of phenotypic features (proposed in the species description below) was found to distinguish these strains from the other Xenorhabdus strains studied (Table 2). Similarly, for group G12, composed of three strains, including the type strain X. szentirmaii DSM 16338T, a combination of phenotypic features was used to distinguish these three strains unambiguously from the other Xenorhabdus strains studied [acid produced from sorbitol, assimilation of D(+)-malate, no lecithinase activity and no assimilation of fructose]. Unlike strain DSM 16348T, strains AR81 and K77 were able to assimilate ribose and to produce acid from fructose, mannose and inositol.
For each of groups G1 (X. ehlersii), G2 (X. budapestensis), G3 (X. innexi), G5 (‘X. indica’) and G11 (X. doucetiae), the phenotypic patterns of the corresponding strains were not grouped together (Fig. 3) and no phenotypic feature could be identified that distinguished these groups unambiguously from the other Xenorhabdus strains studied. However, the biochemical characteristics of the type strain X. ehlersii DSM 16337T defined by Lengyel et al. (2005) were shared by the four new isolates that we assigned to this species, with the exception of assimilation of fructose, arabinose, xylose, rhamnose, phenylacetate and tyrosine, displayed by none of the four isolates. Unlike the type strain X. budapestensis DSM 16342T (Lengyel et al., 2005), strain CN03 produced indole, hydrolysed aesculin, produced acid from acetylglucosamine and assimilated maltotriose, maltose, N-acetyl-D-glucosamine, D-gluconate, L-glutamate, L-proline, L-alanine and L-serine. The biochemical characteristics of the type strain X. innexi DSM 16336T (Lengyel et al., 2005) were shared by strain UY61, but UY61 was also able to assimilate Simmons' citrate and histidine, to produce indole and to ferment inositol. The biochemical characteristics of the proposed type strain ‘X. indica’ DSM 17382 (Somvanshi et al., 2006) were shared by strain OM01, but OM01 was also able to assimilate N-acetyl-D-glucosamine and tyrosine and to hydrolyse aesculin. No combination of phenotypic traits was identified that distinguished strains TH01T, ID10T, USNJ01T, VC01T, Q1T, PR06-AT, X. japonica DSM 16522T or X. beddingii DSM 4764T from the other Xenorhabdus species (Table 2).
Description of Xenorhabdus cabanillasii sp. nov.
Xenorhabdus cabanillasii [ca.ba.nil'la.si.i. N.L. gen. masc. n. cabanillasii in honour of H. E. Cabanillas, who described the nematode host of this bacterium, Steinernema riobrave (Cabanillas et al., 1994)].
The upper temperature limiting growth of the two known strains of this species in LB broth lies between 39 and 40 °C. Assimilates Simmons' citrate, does not hydrolyse aesculin, does not ferment ribose, sorbitol, trehalose or gluconate and does not assimilate ribose, inositol, D-malate, cis-aconitate, D-gluconate, putrescine, lactate, succinate, D-glucosamine, propionate or tyrosine. Known strains are symbiotically associated with the entomopathogenic nematode Steinernema riobrave, from which two geographical ecotypes have been isolated, USTX62T from Texas (USA) and JM26 from the Caribbean island of Jamaica.
The type strain is strain USTX62T (=CIP 109066T=DSM 17905T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is AY521244.
Description of Xenorhabdus doucetiae sp. nov.
Xenorhabdus doucetiae [dou.ce'ti.ae. N.L. gen. fem. n. doucetiae in honour of M. M. A. Doucet, who described the first Steinernema species from South America (Doucet, 1986)].
The upper temperature limiting growth of the two known strains of this species in LB broth lies between 40 and 42 °C. Produces acid from trehalose and assimilates inositol, cis-aconitate and citrate. Known strains are symbiotically associated with the entomopathogenic nematode Steinernema diaprepesi (Nguyen & Duncan, 2002), isolated in Central America and the Caribbean islands.
The type strain is strain FRM16T (=CIP 109074T=DSM 17909T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211709.
Description of Xenorhabdus griffiniae sp. nov.
Xenorhabdus griffiniae [grif.fi'ni.ae. N.L. gen. fem. n. griffiniae in honour of C. T. Griffin, who has contributed to the systematics of the nematode host, Steinernema hermaphroditum (Stock et al., 2004)].
The upper threshold limiting growth in LB broth is 39 °C. Colonies are not pigmented. Does not acidify inositol, sorbitol, maltose, trehalose or gluconate. Assimilates putrescine. The type strain is symbiotically associated with the entomopathogenic nematode Steinernema hermaphroditum, isolated in Indonesia.
The type strain is strain ID10T (=CIP 109073T=DSM 17911T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211710.
Description of Xenorhabdus hominickii sp. nov.
Xenorhabdus hominickii (ho.mi.ni'cki.i. N.L. gen. masc. n. hominickii in honour of W. M. Hominick, who has contributed to the systematics of entomopathogenic nematode–bacterium complexes).
The maximum temperature at which the three known strains of this species can grow is between 33 and 35 °C. Colonies are yellow. Produces indole, an exceptional characteristic in the genus Xenorhabdus, and hydrolyses aesculin. Produces acid from D-malate and 5-ketogluconate and does not assimilate Simmons' citrate, citrate, cis-aconitate, inositol or D-glucosamine. The isolates of this species are symbiotically associated with the entomopathogenic nematodes Steinernema karii (Waturu et al., 1997) and Steinernema monticolum (Stock et al., 1997), from Kenya and Korea, respectively.
The type strain is strain KE01T (=CIP 109072T=DSM 17903T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211719.
Description of Xenorhabdus koppenhoeferi sp. nov.
Xenorhabdus koppenhoeferi [kop.pen.hoe'fe.ri. N.L. gen. masc. n. koppenhoeferi in honour of A. Koppenhöfer, who has contributed to the systematics of the nematode host, Steinernema scarabaei (Stock & Koppenhöfer, 2003)].
The upper temperature limiting growth in LB broth is 33 °C. Colonies are yellow. Produces acid from maltose and 5-ketogluconate. The type strain is symbiotically associated with the entomopathogenic nematode Steinernema scarabaei, isolated from New Jersey (USA).
The type strain is strain USNJ01T (=CIP 109199T=DSM 18168T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ205450.
Description of Xenorhabdus kozodoii sp. nov.
Xenorhabdus kozodoii [ko.zo'do.i.i. N.L. gen. masc. n. kozodoii in honour of E. M. Kozodoi, who described the nematode host Steinernema arenarium (Neoplectana anomali) (Kozodoi, 1984)].
The upper temperature limiting growth of the three known strains of this species in LB broth is between 38 and 41 °C. Produces acid from gluconate and assimilates putrescine. Has no DNase activity and does not assimilate fructose. Does not produce acid from 5-ketogluconate. Known strains are symbiotically associated with the entomopathogenic nematodes Steinernema arenarium and Steinernema apuliae (Triggiani et al., 2004), isolated in Russia and Italy, respectively.
The type strain is strain SaVT (=CIP 109068T=DSM 17907T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211716.
Description of Xenorhabdus mauleonii sp. nov.
Xenorhabdus mauleonii (mau.le.o'ni.i. N.L. gen. masc. n. mauleonii in honour of H. Mauléon, who has made a major contribution to studies of the ecology and biodiversity of entomopathogenic nematode–bacterium complexes in the Caribbean region).
The upper temperature limiting growth in LB broth is 40 °C. Colonies are yellow and assimilate Simmons' citrate and D-malate. Does not assimilate D-glucosamine or tyrosine. The type strain is symbiotically associated with an as-yet-unidentified species of Steinernema isolated from the Caribbean island of St. Vincent.
The type strain is strain VC01T (=CIP 109075T=DSM 17908T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211715.
Description of Xenorhabdus miraniensis sp. nov.
Xenorhabdus miraniensis (mi.ra.ni.en'sis. N.L. fem. adj. miraniensis from Mirani, a small town in Australia, the source of the nematode from which the type strain was isolated).
The upper temperature limiting growth in LB broth is 38 °C. Has no DNase activity and assimilates Simmons' citrate and many carbohydrates, including D-malate, lactate, D-glucosamine, L-aspartate and L-tyrosine. The type strain is symbiotically associated with an as-yet-undescribed nematode of the Steinernematidae (Akhurst & Boemare, 1988) isolated at Mirani in Queensland (Australia) and has not yet been found elsewhere.
The type strain is strain Q1T (=CIP 109069T=DSM 17902T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211713.
Description of Xenorhabdus romanii sp. nov.
Xenorhabdus romanii [ro.ma'ni.i. N.L. gen. masc. n. romanii in honour of J. Román, who described the nematode host Steinernema puertoricense (Román & Figueroa, 1994)].
The upper temperature limiting growth in LB broth is 37 °C. Colonies are yellow and display no DNase activity or aesculin hydrolysis. Does not assimilate histidine and assimilates D-malate inefficiently. The type strain is symbiotically associated with the entomopathogenic nematode Steinernema puertoricense, isolated in Puerto Rico.
The type strain is strain PR06-AT (=CIP 109070T=DSM 17910T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ211717.
Description of Xenorhabdus stockiae sp. nov.
Xenorhabdus stockiae [sto'cki.ae. N.L. gen. fem. n. stockiae in honour of S. P. Stock, a leading figure in the systematics of Steinernema and particularly of the nematode host of this bacterium, Steinernema siamkayai (Stock et al., 1998)].
The upper temperature limiting growth in LB broth is 39 °C. Colonies are pink. Assimilates D-glucosamine and tyrosine in particular, but does not produce acid from trehalose. The type strain is symbiotically associated with the entomopathogenic nematode Steinernema siamkayai, isolated in Thailand.
The type strain is strain TH01T(=CIP 109067T=DSM 17904T). The GenBank accession number of the 16S rRNA gene sequence of the type strain is DQ202309.
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ACKNOWLEDGEMENTS |
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for providing nematodes and/or Xenorhabdus strains. |
REFERENCES |
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TOPABSTRACTMAIN TEXTREFERENCES |
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