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Bacterial strains affiliated to the phylogenetically shallow subcluster C (PnecC) of the 28 Polynucleobacter cluster, which is characterized by a minimal 16S rRNA gene sequence similarity of approx. 98.5 percent, have been reported to occur as obligate endosymbionts of 30 ciliates (Euplotes spp.), as well as to occur as free-living cells in the pelagic zone of freshwater habitats. We investigated if these two groups of closely related bacteria represent 32 strains fundamentally differing in lifestyle, or if they simply represent different stages of a facultative endosymbiotic lifestyle. The phylogenetic analysis of 16S rRNA gene and 16S34 23S ITS sequences of five endosymbiont strains from two different Euplotes species and 40 pure culture strains demonstrated host-species-specific clustering of the endosymbiont 36 sequences within the PnecC subcluster. The sequences of the endosymbionts showed characteristics indicating an obligate endosymbiotic lifestyle. Cultivation experiments 38 revealed fundamental differences in physiological adaptations, and determination of the genome sizes indicated a slight size reduction in endosymbiotic strains. We conclude that the 40 two groups of PnecC bacteria represent obligately free-living and obligately endosymbiotic strains, respectively, and do not represent different stages of the same complex lifecycle. 42 These closely related strains occupy completely separated ecological niches. To our best knowledge, this is the closest phylogenetic relationship between obligate endosymbionts and 44 obligately free-living bacteria ever revealed.

The white-clawed crayfish is a complex of species (Austropotamobius pallipes plus A. italicus, Crustacea) pivotal to riverine environments. Regrettably, it is endangered in many European countries due to a recent massive decline. We carried out a fine-scale survey on white-clawed crayfish distribution, morphology and genetics in an under-investigated region of central Italy (Lunigiana, Tuscany) to improve local knowledge and aid conservation management of the species. The torrential fauna of Lunigiana is scarcely known and habitat alterations due to the anthropic exploitation of the territory represent a potential threat to its persistence. We investigated crayfish occurrence in eight streams of the Magra River Basin. We performed nocturnal and diurnal transects, took morphometric measurements, collected samples for genetic analysis and checked for the occurrence of ectosymbionts. Crayfish were disclosed in two streams (Civasola, Verdesina). Morphometric and phylogenetic analysis (mtDNA COI gene Bayesian tree reconstruction) concurrently identified both populations as Austropotamobius italicus carinthiacus. In the Verdesina stream, crayfish were heavily infested by branchiobdellidans (Annelida). Verdesina crayfish were also significantly smaller than those found in the Civasola stream, where branchiobdellidans were absent. Hence, we hypothesized that such difference in size might be related to the high density of ectosymbionts. In the light of habitat features and of data herein provided, we propose that both Civasola and Verdesina streams should be considered as “natural ark sites” for A. italicus, with the Magra River Basin representing a regional stronghold for the conservation of the species.

During faunal studies of psammophilic ciliates along the coast of Qingdao, China, several marine karyorelictean species were isolated. Among them, four species within the genus Remanella were investigated, including two species new to science: i.e., R. rugosa, Remanella elongata sp. nov., Remanella aposinica sp. nov., and R. unicorpusculata. Remanella rugosa has been reported several times, but this study is the first to provide detailed morphological characters and phylogenetics. Remanella elongata sp. nov. can be distinguished from its congeners by the presence of complex cortical granules, fewer macronuclei, and longer body size. Remanella aposinica sp. nov. differs from its congeners by having 14–17 right lateral ciliary rows and 24–37 dikinetids of intrabuccal kinety. Poorly known Remanella rugosa var. unicorpusculata (Kahl, 1933) Foissner, 1996 should be elevated from subspecies to species level, Remanella unicorpusculata (Foissner, 1996) stat. nov., based on detailed redescriptions with statistical data, living morphology, infraciliature, and species definitions. Small subunit (SSU) rDNA was sequenced for the four species, and phylogenetic analysis revealed that all known taxa in Remanella formed the outline branch to the genus Loxodes with moderate to high bootstrap support among Remanella lineages. [ABSTRACT FROM AUTHOR]

In the past, studies on the relationships of the bacterial phyla Planctomycetes, Chlamydiae, Lentisphaerae, and Verrucomicrobia using different phylogenetic markers have been controversial. Investigations based on 16S rRNA sequence analyses suggested a relationship of the four phyla, showing the branching order Planctomycetes, Chlamydiae, Verrucomicrobia/Leutisphaerae. Phylogenetic analyses of 23S rRNA genes in this study also support a monophyletic grouping and their branching order--this grouping is significant for understanding cell division, since the major bacterial cell division protein FtsZ is absent from members of two of the phyla Chlamydiae and Planctomycetes. In Verrucomicrobia, knowledge about cell division is mainly restricted to the recent report of ftsZ in the closely related genera Prosthecobacter and Verrucomicrobium. In this study, genes of the conserved division and cell wall (dcw) cluster (ddl, ftsQ, ftsA, and ftsZ) were characterized in all verrucomicrobial subdivisions (1 to 4) with cultivable representatives (1 to 4). Sequence analyses and transcriptional analyses in Verrucomicrobia and genome data analyses in Lentisphaerae suggested that cell division is based on FtsZ in all verrucomicrobial subdivisions and possibly also in the sister phylum Lentisphaerae. Comprehensive sequence analyses of available genome data for representatives of Verrucomicrobia, Lentisphaerae, Chlamydiae, and Planctomycetes strongly indicate that their last common ancestor possessed a conserved, ancestral type of dcw gene cluster and an FtsZ-based cell division mechanism. This implies that Planctomycetes and Chlamydiae may have shifted independently to a non-FtsZ-based cell division mechanism after their separate branchings from their last common ancestor with Verrucomicrobia.

Two new bacteria belonging to the 'Candidatus Midichloria' clade hosted by two different strains of the cilicate protist Euplotes harpa, are described on the basis of ultrastructural observations, comparative 16S rRNA gene sequence analysis and an estimation of the percentage of infection. The data obtained for the two ciliate-borne bacteria are proposed to be belonging to the 'Candidatus Midichloria' clade 'Candidatus Anadelfobacter veles' and 'Candidatus Cyrtobacter comes'.