Reclassification of Leptospira parva Hovind-Hougen et al. 1982 as Turneriella parva gen. nov., comb. nov.

Abstract

Analysis of the G+C content, DNADNA relatedness to other leptospires and 16S rRNA gene sequence of Leptospira parva showed that this species was not related to other Leptospira species. On the basis of these data, it is proposed that Leptospira parva should be transferred to the genus Turneriella as Turneriella parva gen. nov., comb. nov., with strain H^T (=NCTC 11395^T=ATCC BAA-1111^T) as the type strain.

Published online ahead of print on 17 February 2005 as DOI 10.1099/ijs.0.63088-0.

The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains H^T and S-308-81 are AY293856 and AY398688, respectively.

We thank Professor Dr Hans Trüper for his kind advice regarding the etymology of the genus name.

Footnotes

†Present address: Provincial Laboratory, Saskatchewan Health, 3211 Albert Street, Regina, Saskatchewan, Canada S4S 5W6.

Leptospires were traditionally classified as belonging to two species, Leptospira interrogans and Leptospira biflexa, comprising pathogenic and non-pathogenic strains, respectively (Johnson & Faine, 1984). A more complex classification, based upon DNADNA relatedness, recognizes 13 species with validly published names and four as yet unnamed genomospecies (Brenner et al., 1999; Perolat et al., 1998; Ramadass et al., 1992; Yasuda et al., 1987).

Leptospira parva strain H^T was isolated from contaminated bovine albumin liquid culture medium, and was recognized as being distinct from strains belonging to both existing species of the genus Leptospira (Hovind-Hougen et al., 1981). Moreover, the G+C content differed markedly from that of strains of other Leptospira species (Hovind-Hougen et al., 1981). That Leptospira parva was not closely related to other species within the genus was further confirmed by DNADNA relatedness studies (Yasuda et al., 1987) and 16S rRNA gene sequencing (Hookey et al., 1993) (Fig. 1).

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Fig. 1. Phylogenetic relationships between the genera of the family Leptospiraceae. The unrooted tree was obtained by neighbour-joining 16S rRNA gene sequences representing the leptospiral clades, Leptonema illini and T. parva. The 16S rRNA genes of strains of known species were resequenced to near full-length and high redundancy before further analysis. Neighbour-joining was implemented on CLUSTAL_X-aligned sequences, with branch placement analysed by bootstrapping 1000 times for confidence resulting in all branch values of 1000 (not shown). The tree was drawn using TreeExplorer. Bar, 29 nucleotide substitutions per 1454 aligned base pairs. GenBank/EMBL/DDBJ accession numbers are as follows. Pathogenic Leptospira spp.: Leptospira borgpetersenii serovar Ballum strain Mus 127, AY631884. Intermediate Leptospira spp.: Leptospira inadai serovar Lyme^T, AY631896; Leptospira fainei serovar Hurstbridge strain BUT 6^T, AY631885. Saprophytic Leptospira species: Leptospira biflexa serovar Patoc strain Patoc I^T, AY631876. Leptonema illini serovar Illini strain 3055^T, AY714984. T. parva strain H^T, AY293856.

A second strain, S-308-81 (=ATCC BAA-1112), was isolated from the uterus of a sow in Northern Ireland. The 16S rRNA gene sequence of this strain was found to be identical to that of strain H^T. DNA was extracted from strains H^T and S-308-81 and purified, as described previously (Brenner et al., 1982). DNA from strain H^T was labelled with [³²P]dCTP (Brenner et al., 1999), and the DNADNA relatedness and percentage divergence between the two strains were determined by using the hydroxyapatite method, at an optimal reassociation temperature of 55 °C. The DNADNA relatedness (relative binding ratio) was 81 % and the percentage divergence in related DNA sequences was 0·2 % (Table 1). These two strains meet the criteria for the molecular definition of a species (Brenner et al., 1999). DNADNA relatedness studies (Table 1) have shown Leptospira parva strain H^T to be distinct from strains of other Leptospira species and from Leptonema illini (Brenner et al., 1999).

Table 1. DNADNA relatedness between T. parva HT and reference strains of Leptospira species and Leptonema illini

A proposal was made at the ICSB Subcommittee on the Taxonomy of Leptospira (TSC) meeting in 1990 to transfer Leptospira parva from the genus Leptospira to a newly created genus, Turneria, as Turneria parva (Marshall, 1992). This proposal was agreed to at the TSC meeting, but apparently was not prepared for publication, so the name currently has no standing in nomenclature. The nomenclature of this species has become a source of confusion, with some authors referring incorrectly to Leptospira parva as Leptospira parva incertae sedis (Hookey, 1993) and others using the genus name Turneria, which has no standing in nomenclature. Moreover, the genus name Turneria is illegitimate because it is the name of genera of both plants (Dicotyledones: Turneraceae) and animals (Formicidae, Hymenoptera and Sauropterygia, Reptilia).

In order to clarify this situation, we propose the transfer of Leptospira parva to the genus Turneriella as Turneriella parva gen. nov., comb. nov., with strain H^T as the type strain (Hovind-Hougen et al., 1981). We believe that this fulfils the original intention of the proposal minuted from the 1990 TSC meeting (Marshall, 1992). The description of T. parva is given below, and the description of the family Leptospiraceae Hovind-Hougen 1979 is emended, to take into account the proposed changes.

Emended description of Leptospiraceae Hovind-Hougen 1979
Comprises three genera, Leptospira, Leptonema and Turneriella, defined by differences in G+C content, DNADNA relatedness and 16S rRNA gene sequences. The G+C contents of the genera Leptospira, Leptonema and Turneriella are 3343, 54 and 48 mol%, respectively (Yasuda et al., 1987). Other characteristics are as described previously (Hovind-Hougen, 1979; Johnson & Faine, 1984). The type genus is Leptospira Noguchi 1917.

Description of Turneriella gen. nov.
Turneriella (Tur'ne.ri.el.la. N.L. fem. n. Turneriella to honour Leslie Turner, an English medical microbiologist who made definitive contributions to the knowledge of leptospirosis).

Cells are Gram-negative, flexible and helical, measuring 0·3x3·57·5 µm; wavelength is 0·30·5 µm (Hovind-Hougen et al., 1981). Motile by means of two axial filaments. Obligately aerobic. Oxidase-positive. The type species is Turneriella parva (Hovind-Hougen et al. 1982) Levett et al. 2005.

Description of Turneriella parva comb. nov.
Turneriella parva (par'va. L. fem. adj. parva small).

Basonym: Leptospira parva Hovind-Hougen et al. 1982.

Exhibits the following characteristics in addition to those given in the genus description. DNA G+C content is 48 mol% (Yasuda et al., 1987). Growth is inhibited by 200 µg 8-azaguanine ml¹ and 10 µg 2,6-diamonopurine ml¹. Produces lipase. Grows at 13, 30 and 37 °C after prolonged incubation. Strains have been isolated from contaminated culture medium, from tap water and from the uterus of a sow. Not pathogenic for hamsters. The type strain is H^T (=NCTC 11395^T=ATCC BAA-1111^T).

Abstract

Footnotes

References