General Medicine

Phylogenetic analysis and phenotypic characterization were used to assign a multicellular magnetotactic prokaryote the name ‘Candidatus Magnetoglobus multicellularis’. ‘Candidatus Magnetoglobus multicellularis' lives in a large hypersaline coastal lagoon from Brazil and has properties that are unique among prokaryotes. It consists of a compact assembly or aggregate of flagellated bacterial cells, highly organized in a sphere, that swim in either helical or straight trajectories. The life cycle of ‘Candidatus Magnetoglobus multicellularis' is completely multicellular, in which one aggregate grows by enlarging the size of its cells and approximately doubling the volume of the whole organism. Cells then divide synchronously, maintaining the spherical arrangement; finally the cells separate into two identical aggregates. Phylogenetic 16S rRNA gene sequence analysis showed that ‘Candidatus Magnetoglobus multicellularis' is related to the dissimilatory sulfate-reducing bacteria within the Deltaproteobacteria and to other previously described, but not yet well characterized, multicellular magnetotactic prokaryotes.

Filamentous bacteria frequently occurring in the pelagic zone of natural freshwater lakes and ponds were previously identified as being related to Haliscomenobacter hydrossis based upon their 16S rRNA gene sequences. These bacteria exhibit a specific morphology characterized by the formation of straight, stick-like filaments of variable length (5 to >100 μm) and quite stable, but narrow, width (0.25 to 0.35 μm). Bacteria with these morphological characteristics form a monophyletic but broad phylogenetic group with a maximal divergence of 16S rRNA gene sequences of 12.0 %. This monophyletic group consists of at least three monophyletic subclusters. H. hydrossis is affiliated to one of these subclusters and represents the sole recognized species affiliated to the broad monophyletic group. ‘Candidatus Haliscomenobacter calcifugiens' and ‘Candidatus Aquirestis calciphila’ are uncultured representatives of the other two subclusters and have 16S rRNA gene sequence dissimilarities of 5.4 % and 8.2 %, respectively, with the type strain of H. hydrossis. ‘Candidatus H. calcifugiens' and ‘Candidatus A. calciphila’ have a 16S rRNA gene sequence dissimilarity of 8.5 %. These large ribosomal divergences justify the classification of these environmentally important bacteria as a novel species and a new genus, respectively. Intensive attempts to cultivate these filamentous bacteria have resulted in the establishment of mixed cultures, however, attempts to establish pure cultures have failed.

Six strains (CB7T, CB18, CB23, CB26, CB28 and CB35T) were isolated from human faeces. Based on phylogenetic analysis, phenotypic characteristics, cellular fatty acid profiles and menaquinone profiles, these strains could be included within the genusPrevotellaand made up two clusters. 16S rRNA gene sequence analysis indicated that five strains were most closely related toPrevotella veroralis, sharing about 92 % sequence similarity; the remaining strain was most closely related toPrevotella shahii, sharing about 90 % sequence similarity. All six strains were obligately anaerobic, non-pigmented, non-spore-forming, non-motile, Gram-negative rods. The cellular fatty acid compositions of the six strains differed significantly from those of otherPrevotellaspecies. Five strains (CB7T, CB18, CB23, CB26 and CB28) contained dimethyl acetals and the major menaquinones of these strains were MK-11, MK-12 and MK-13. The major menaquinones of CB35Twere MK-12 and MK-13. Based on phenotypic and phylogenetic findings, two novel species,Prevotella coprisp. nov. andPrevotella stercoreasp. nov., are proposed, representing the two different strain clusters. The DNA G+C contents of strains CB7Tand CB35Twere 45.3 and 48.2 mol%, respectively. The type strains ofP. copriandP. stercoreaare CB7T(=JCM 13464T=DSM 18205T) and CB35T(=JCM 13469T=DSM 18206T), respectively.

Four formate-utilizing methanogens were isolated from ovine (strain KM1H5-1PT) and bovine (strains AK-87, OCP and ZA-10T) rumen contents. Based on 16S rRNA gene sequence analysis, the methanogen strains were found to belong to the order Methanobacteriales in the genus Methanobrevibacter. Strains ZA-10T and KM1H5-1PT gained energy for growth by the reduction of CO2 to CH4 using H2 or formate exclusively as electron donors. Increasing formate concentrations to 220 mM in batch cultures increased the growth of strain KM1H5-1PT but did not affect the growth of strain ZA-10T. Substrate specificity and resistance to cell-wall lysis supported the affiliation of the strains to the genus Methanobrevibacter. Strains ZA-10T and KM1H5-1PT showed 16S rRNA gene sequence similarity of 98.0 and 98.6 % to their closest recognized relatives, Methanobrevibacter thaueri CWT and Methanobrevibacter ruminantium M1T, respectively. DNA–DNA hybridization experiments indicated that the strains were not affiliated at the species level to their closest recognized relatives, with DNA reassociation values of only 28 % between strains ZA-10T and Methanobrevibacter thaueri CWT and <25 % between strains KM1H5-1PT and Methanobrevibacter ruminantium M1T. Based on the data presented, the new strains are considered to represent two novel species of the genus Methanobrevibacter, for which the names Methanobrevibacter millerae sp. nov. (type strain ZA-10T=DSM 16643T=OCM 820T) and Methanobrevibacter olleyae sp. nov. (type strain KM1H5-1PT=DSM 16632T=OCM 841T) are proposed.

A Gram-negative, chemoheterotrophic, facultatively anaerobic coccus, designated IMCC1545T, was isolated from the digestive tract of a marine clamworm, Periserrula leucophryna, inhabiting a tidal flat of the Yellow Sea. Cells of strain IMCC1545T are non-motile, dividing by binary fission. The predominant fatty acids are anteiso-C15 : 0 and C18 : 0. The respiratory quinone is menaquinone-7 and the DNA G+C content is 52.1 mol%. Phylogenetic analyses based on 16S rRNA gene sequences using three treeing algorithms revealed that the strain formed a novel genus-level lineage within the phylum ‘Verrucomicrobia’. The most closely related named organisms to strain IMCC1545T are ‘Fucophilus fucoidanolyticus’ SI-1234 (86.5 % 16S rRNA gene sequence similarity), Alterococcus agarolyticus ADT3T (81.8 %) and Opitutus terrae PB90-1T (80.3 %), which belong to subdivision 4 of the ‘Verrucomicrobia’. Subdivision 4 of the ‘Verrucomicrobia’ (here named Opitutae classis nov.) was divided into two clades, a clade containing strain IMCC1545T and a clade containing Opitutus terrae. From the taxonomic data obtained in this study, it is proposed that the new marine isolate be placed into a novel genus and species named Puniceicoccus vermicola gen. nov., sp. nov. (the type strain of Puniceicoccus vermicola is IMCC1545T=KCCM 42343T=NBRC 101964T) within Puniceicoccaceae fam. nov and Puniceicoccales ord. nov in the class Opitutae. The family Opitutaceae fam. nov. and order Opitutales ord. nov. are also formally proposed.

An intracellular bacterium with the unique ability to enter mitochondria exists in the European vector of Lyme disease, the hard tick Ixodes ricinus. Previous phylogenetic analyses based on 16S rRNA gene sequences suggested that the bacterium formed a divergent lineage within the Rickettsiales (Alphaproteobacteria). Here, we present additional phylogenetic evidence, based on the gyrB gene sequence, that confirms the phylogenetic position of the bacterium. Based on these data, as well as electron microscopy (EM), in situ hybridization and other observations, we propose the name ‘Candidatus Midichloria mitochondrii’ for this bacterium. The symbiont appears to be ubiquitous in females of I. ricinus across the tick's distribution, while lower prevalence is observed in males (44 %). Based on EM and in situ hybridization studies, the presence of ‘Candidatus M. mitochondrii’ in females appears to be restricted to ovarian cells. The bacterium was found to be localized both in the cytoplasm and in the intermembrane space of the mitochondria of ovarian cells. ‘Candidatus M. mitochondrii’ is the first bacterium to be identified that resides within animal mitochondria.

The taxonomic position of a group of mesophilic actinomycetes isolated from arid Australian soils was determined using a polyphasic approach. The organisms shared chemical and morphological markers typical of members of the genus Amycolatopsis. They had identical 16S rRNA gene sequences and formed a distinct phyletic line in the Amycolatopsis mediterranei clade, being most closely related to A. mediterranei. In addition, they shared a range of phenotypic properties that distinguished them from representatives of all of the species classified in this clade. The combined genotypic and phenotypic data indicate that the strains merit species status within the genus Amycolatopsis. The name proposed for the novel species is Amycolatopsis australiensis sp. nov.; the type strain is GY048T (=DSM 44671T=NCIMB 14142T).