Publications

4749

‘Candidatus Phytoplasma cynodontis’ is widespread in bermudagrass and has only been found in monocotyledonous plants. Molecular studies carried out on strains collected in Italy, Serbia, and Albania enabled verification of molecular variability in the 16S ribosomal RNA (rRNA) gene. Based on restriction fragment length polymorphism and sequence analyses, the strains from Serbia were clearly differentiated from all others and assigned to a new ribosomal DNA (rDNA) subgroup designated as 16SrXIV-C. A system for amplification of fragments containing the ‘Ca. P. cynodontis’ groEL gene was developed to enable study of its variability in related strains belonging to different 16SrXIV subgroups. Despite the fact that the groEL gene exhibited a greater sequence variation than 16S rRNA, the phylogenetic tree based on groEL gene sequence analysis was highly congruent with the 16S rDNA-based tree. The groEL gene analyses supported differentiation of the Serbian strains and definition of the new subgroup 16SrXIV-C. Phylogenetic analyses of both genes confirmed distinct phylogenetic lineages for strains belonging to 16SrXIV subgroups. Furthermore, groEL is the only nonribosomal marker developed for characterization of ‘Ca. P. cynodontis’ thus far, and its application in molecular surveys should provide better insight into the relationships among these phytoplasmas and correlation between strain differentiation and their geographical distribution.

Abstract The bacterial family Rickettsiaceae includes a group of well-known etiological agents of many human and vertebrate diseases, including epidemic typhus-causing pathogen Rickettsia prowazekii. Owing to their medical relevance, rickettsiae have attracted a great deal of attention and their host-pathogen interactions have been thoroughly investigated. All known members display obligate intracellular lifestyles, and the best-studied genera, Rickettsia and Orientia, include species that are hosted by terrestrial arthropods. Their obligate intracellular lifestyle and host adaptation is reflected in the small size of their genomes, a general feature shared with all other families of the Rickettsiales. Yet, despite that the Rickettsiaceae and other Rickettsiales families have been extensively studied for decades, many details of the origin and evolution of their obligate host-association remain elusive. Here we report the discovery and single-cell sequencing of ‘Candidatus Arcanobacter lacustris’, a rare environmental alphaproteobacterium that was sampled from Damariscotta Lake that represents a deeply rooting sister lineage of the Rickettsiaceae. Intriguingly, phylogenomic and comparative analysis of the partial ‘Candidatus Arcanobacter lacustris’ genome revealed the presence chemotaxis genes and vertically inherited flagellar genes, a novelty in sequenced Rickettsiaceae, as well as several host-associated features. This finding suggests that the ancestor of the Rickettsiaceae might have had a facultative intracellular lifestyle. Our study underlines the efficacy of single-cell genomics for studying microbial diversity and evolution in general, and for rare microbial cells in particular.

ABSTRACT Chemoautotrophic marine bacteria from the SUP05 clade of marine gammaproteobacteria often dominate low-oxygen waters in upwelling regions, fjords, and hydrothermal systems. Here, we announce the complete genome sequence of “ Candidatus Thioglobus autotrophica” strain EF1, the first cultured chemoautotrophic representative from the SUP05 clade.

ABSTRACT “ Candidatus Phytoplasma pruni” strain CX, belonging to subgroup 16SrIII-A, is a plant-pathogenic bacterium causing economically important diseases in many fruit crops. Here, we report the draft genome sequence, which consists of 598,508 bases, with a G+C content of 27.21 mol%.

ABSTRACT Mixotrophic marine bacteria from the SUP05 clade are ubiquitous in the ocean. Here, we announce the complete genome sequence of “ Candidatus Thioglobus singularis” strain PS1, the first cultured mixotrophic representative from the SUP05 clade.

The phenotypic and genotypic characteristics of four Bordetella hinzii-like strains from human respiratory specimens and representing nrdA gene sequence based genogroups 3, 14 and 15 were examined. In a 16S rRNA gene sequence based phylogenetic tree, the four strains consistently formed a single coherent lineage but their assignment to the genus Bordetella was equivocal. The respiratory quinone, polar lipid and fatty acid profiles generally conformed to those of species of the genus Bordetella and were characterized by the presence of ubiquinone 8, of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and several aminolipids, and of high percentages of C16 : 0, cyclo-C17 : 0 and summed feature 2, as major chemotaxonomic marker molecules, respectively. The DNA G+C content was about 66 mol%, which corresponded with that of the high-percentage DNA G+C content genera of the family Alcaligenaceae including the genus Bordetella. DNA–DNA hybridization experiments revealed the presence of three distinct genomospecies and thus confirmed phenotypic differences as revealed by means of extensive biochemical characterization. We therefore propose to formally classify Bordetella genogroups 3, 14 and 15 as Bordetella bronchialis sp. nov. (type strain LMG 28640T = AU3182T = CCUG 56828T), Bordetella sputigena sp. nov. (type strain LMG 28641T = CCUG 56478T) and Bordetella flabilis sp. nov. (type strain LMG 28642T = AU10664T = CCUG 56827T). In addition, we propose to reclassify Achromobacter sediminum into the novel genus Verticia, as Verticia sediminum, gen. nov., comb. nov., on the basis of its unique phylogenetic position, its marine origin and its distinctive phenotypic, fatty acid and polar lipid profile.

ABSTRACT “ Candidatus Neoehrlichia mikurensis” is the tick-borne agent of neoehrlichiosis, an infectious disease that primarily affects immunocompromised patients. So far, the genetic variability of “ Ca . Neoehrlichia” has been studied only by comparing 16S rRNA genes and groEL operon sequences. We describe the development and use of a multilocus sequence analysis (MLSA) protocol to characterize the genetic diversity of clinical “ Ca . Neoehrlichia” strains in Europe and their relatedness to other species within the Anaplasmataceae family. Six genes were selected: ftsZ , clpB , gatB , lipA , groEL , and 16S rRNA. Each MLSA locus was amplified by real-time PCR, and the PCR products were sequenced. Phylogenetic trees of MLSA locus relatedness were constructed from aligned sequences. Blood samples from 12 patients with confirmed “ Ca . Neoehrlichia” infection from Sweden ( n = 9), the Czech Republic ( n = 2), and Germany ( n = 1) were analyzed with the MLSA protocol. Three of the Swedish strains exhibited identical lipA sequences, while the lipA sequences of the strains from the other nine patients were identical to each other. One of the Czech strains had one differing nucleotide in the clpB sequence from the sequences of the other 11 strains. All 12 strains had identical sequences for the genes 16S rRNA, ftsZ , gatB , and groEL . According to the MLSA, among the Anaplasmataceae , “ Ca . Neoehrlichia” is most closely related to Ehrlichia ruminantium , less so to Anaplasma phagocytophilum , and least to Wolbachia endosymbionts. To conclude, three sequence types of infectious “ Ca . Neoehrlichia” were identified: one in the west of Sweden, one in the Czech Republic, and one spread throughout Europe.