Strong phospholipase A (PLA) and phospholipase C (PLC) activities as potential virulence factors are the outstanding characteristics of eight strains of small oral spirochaetes isolated from deep periodontal lesions. By qualitative dot-blot DNA-DNA hybridization and 16S rDNA sequence comparison, these spirochaetes form a distinct phylogenetic group, with Treponema maltophilum as its closest cultivable relative. Growth of these treponemes, cells of which contain two endoflagella, one at each pole, was autoinhibited by the PLA-mediated production of lysolecithin unless medium OMIZ-Pat was prepared without lecithin. N-Acetylglucosamine was essential and d-ribose was stimulatory for growth. All isolates were growth-inhibited when 1% foetal calf serum was added to the medium. Growth on agar plates supplemented with human erythrocytes produced haemolysis. In addition to PLA and PLC, the new isolates displayed strong activities of alkaline and acid phosphatases, β-galactosidase, β-glucuronidase, N-acetyl-β-glucosaminidase and sialidase, intermediate activities of C4- and C8-esterases, naphthol phosphohydrolase and α-fucosidase and a distinctive 30 kDa antigen detectable on Western blots. This phenotypically and genotypically homogeneous group is proposed as a novel species, Treponema lecithinolyticum sp. nov., with isolate OMZ 684T designated as the type strain. A molecular epidemiological analysis using a T. lecithinolyticum-specific probe showed this organism to be associated with affected sites when compared with unaffected sites of periodontitis patients. This association was more pronounced in patients with rapidly progressive periodontitis than in those with adult periodontitis.

The detailed phylogenetic relationships for genus Marinilabilia and related taxa were analysed by using DNA gyrase B subunit gene (gyrB) sequences. Anaerobic bacteria in the Cytophaga-Flavobacterium-Bacteroides phylum, namely genera Marinilabilia, Bacteroides, Rikenella, Prevotella and Porphyromonas and Cytophaga fermentans, were clustered in the same branch and the facultative anaerobes Marinilabilia and Cytophaga fermentans formeed a subcluster in the branch of the anaerobic bacteria. Phylogenetic analysis using 16S rDNA sequences gave a similar result but with a lower bootstrap value for each cluster. The gyrB sequences of Marinilabilia salmonicolor and Marinilabilia agarovorans were the same, and the relatedness of their chromosomal DNA, as determined by DNA-DNA hybridization, was greater than 70%. These genetic aspects led to the conclusion that M. salmonicolor IFO 15948T and M. agarovorans IFO 14957T belong to a single species. Since M. salmonicolor was described first, as Cytophaga salmonicolor, M. salmonicolor is a senior subjective synonym of M. agarovorans. Therefore, the name M. salmonicolor should be retained and strain IFO 14957T should be reclassified as M. salmonicolor. However, the agar-degrading ability of strain IFO 14957T is a prominent biochemical characteristic. It is therefore proposed that strain IFO 14957T should be renamed M. salmonicolor biovar agarovorans.

Phytoplasmas associated with the plant diseases ash yellows (AshY, occurring in Fraxinus) and lilac witches'-broom (LWB, occurring in Syringa) represent a putative species-level taxon. Phytoplasmal DNA from 19 ash or lilac sources across the known geographic range of AshY (71–113 °W) was examined to determine if AshY and LWB phytoplasmas are a coherent group, if variability exists in both conserved and anonymous DNA, and if variability in 16S rDNA is related to host or geographic origin. The 16S rRNA gene and the 16S-23S spacer were amplified using primer pair P1/P7 and analysed using 15 restriction enzymes. RFLPs were detected in digests obtained with Alul, Hhal or Taql, for a total of four RFLP profile types. Sequencing of the amplimers from strains AshY1T, AshY3, AshY5 and LWB3 (which represent the four 16S rDNA RFLP profile types) revealed only three positions in the 16S rRNA gene and one position in the 16S-23S spacer at which differences occurred; these were single nucleotide substitutions. Sequence homology between any two strains was >99.8%. A portion of a ribosomal protein operon, amplified with primer pair rpF1/R1 from each of the four strains noted above, was analysed with six restriction enzymes, resulting in the detection of two RFLP profiles with Msel. Southern analysis, utilizing two non-specific probes from other phytoplasma groups, revealed three RFLP profile types in anonymous chromosomal DNA of strains representing the four 16S rDNA genotypes. Two strains, AshY3 and LWB3, had unique combinations of characters in the various assays. On the basis of RFLP profiles, the strains from the other plants sampled comprised two groups. The grouping was not clearly related to host or geographic origin. The genome size of strain AshY3 was estimated from PFGE data to be 645 kbp. Phylogenetic analysis of a 1423 bp 16S rDNA sequence from strains AshY1T, AshY3, AshY5 and LWB3, together with sequences from 14 other mollicutes archived in GenBank, produced a tree on which the AshY and LWB strains clustered as a discrete group, consistent with previous analyses utilizing only type strain AshY1T. Thus, the AshY phytoplasma group is coherent but heterogeneous. The name ‘Candidatus Phytoplasma fraxini’ is proposed for this group.