Publications

4870

Summary Accumulating evidence supports a role for Chlamydia ‐related organisms as emerging pathogens for human and animals. Assessment of their pathogenicity requires strain availability, at least for animal models and serological studies. As these obligate intracellular species are able to grow inside amoebae, we used co‐culture with Acanthamoeba castellanii in an attempt to recover new Chlamydia ‐related species from river water. We isolated two strains from eight water samples. The first strain is a new Parachlamydia acanthamoebae strain that differs from previously described isolates by only two bases in the complete 16S rRNA gene sequence. The second isolate is the first representative of a new Chlamydiales family, as demonstrated by genetic and phylogenetic analyses of the 16S rRNA, 23S rRNA, ADP/ATP translocase and RnpB encoding genes. Using fluorescent in situ hybridization and electron microscopy, we demonstrated that it grows in high numbers in amoebae, where it exhibits a Chlamydia ‐like developmental cycle with reticulate bodies and star‐like elementary bodies. Based on these results, we propose to name this new species ‘ Criblamydia sequanensis ’. This work confirmed that amoebal co‐culture is a relevant method to isolate new chlamydiae, and that it can be successfully applied to ecosystems colonized with a complex microbial community.

ABSTRACT Laser capture microdissection in combination with fluorescent in situ hybridization was used to identify an unknown species of spirochetes from the pig colonic mucosa. The 16S rRNA gene was PCR amplified, and the closest related type strain was Treponema bryantii T (90.1%). The spirochete, here named “ Candidatus Treponema suis, ” was associated with colitis, including invasion of the surface epithelium as well as superficial parts of the mucosa.

ABSTRACTTwo hemotropic mycoplasmas have been recognized in cats,Mycoplasma haemofelisand “CandidatusMycoplasma haemominutum.” We recently described a third feline hemoplasma species, designated “CandidatusMycoplasma turicensis,” in a Swiss cat with hemolytic anemia. This isolate induced anemia after experimental transmission to two specific-pathogen-free cats and analysis of the 16S rRNA gene revealed its close relationship to rodent hemotropic mycoplasmas. The agent was recently shown to be prevalent in Swiss pet cats. We sought to investigate the presence and clinical importance of “CandidatusMycoplasma turicensis” infection in pet cats outside of Switzerland and to perform the molecular characterization of isolates from different countries. A “CandidatusMycoplasma turicensis”-specific real-time PCR assay was applied to blood samples from 426 United Kingdom (UK), 147 Australian, and 69 South African pet cats. The 16S rRNA genes of isolates from different countries were sequenced and signalment and laboratory data for the cats were evaluated for associations with “CandidatusMycoplasma turicensis” infection. Infections were detected in samples from UK, Australian, and South African pet cats. Infection was associated with the male gender, and “CandidatusMycoplasma haemominutum” andM. haemofeliscoinfection. Coinfected cats exhibited significantly lower packed cell volume (PCV) values than uninfected cats. Phylogenetic analyses revealed that some Australian and South African “CandidatusMycoplasma turicensis” isolates branched away from the remaining isolates. In summary, “CandidatusMycoplasma turicensis” infection in pet cats exists over a wide geographical area and significantly decreased PCV values are observed in cats coinfected with other feline hemoplasmas.

ABSTRACT The symbiotic bacteria associated with the stomach disc, a large aggregate of bacteriocytes on the ventral side of the midgut, of human body and head lice were characterized. Molecular phylogenetic analysis of 16S rRNA gene sequences showed that the symbionts formed a distinct and well-defined clade in the Gammaproteobacteria . The sequences exhibited AT-biased nucleotide composition and accelerated molecular evolution. In situ hybridization revealed that in nymphs and adult males, the symbiont was localized in the stomach disc, while in adult females, the symbiont was not in the stomach disc but in the lateral oviducts and the posterior pole of the oocytes due to female-specific symbiont migration. We propose the designation “ Candidatus Riesia pediculicola” for the louse symbionts.

ABSTRACTTo survive in host cells, intracellular pathogens or symbiotic bacteria require protective mechanisms to overcome the oxidative stress generated by phagocytic activities of the host. By genomic library tagging, we cloned adps(stands forDNA-bindingprotein fromstarved cells) gene of the symbiotic “CandidatusLegionella jeonii” organism (called the X bacterium) (dpsX) that grows inAmoeba proteus. The gene encodes a 17-kDa protein (pI 5.19) with 91% homology to Dps and DNA-binding ferritin-like proteins of other organisms. The cloned gene complemented thedpsmutant ofEscherichia coliand conferred resistance to hydrogen peroxide. DpsXproteins purified fromE. colitransformed with thedpsXgene were in oligomeric form, formed a complex with pBlueskript SKII DNA, and protected the DNA from DNase I digestion and H2O2-mediated damage. The expression of thedpsXgene in “CandidatusLegionella jeonii” was enhanced when the host amoeba was treated with 2 mM H2O2and by phagocytic activities of the host cell. These results suggested that the Dps protein has a function protective of the bacterial DNA and that its gene expression responds to oxidative stress generated by phagocytic activities of the host cell. With regard to the fact that invasion ofLegionellasp. into respiratory phagocytic cells causes pneumonia in mammals, further characterization ofdpsXexpression in theLegionellasp. that multiplies in a protozoan host in the natural environment may provide valuable information toward understanding the protective mechanisms of intracellular pathogens.

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.

Two Gram-positive bacilli, designated as strains SMC 4352-1T and SMC 4352-2T, were isolated sequentially from the blood of a newborn child with sepsis. They could not be identified by using conventional clinical microbiological methods. 16S rRNA gene sequencing and phylogenetic analysis revealed that both strains belonged to the genus Bacillus but clearly diverged from known Bacillus species. Strain SMC 4352-1T and strain SMC 4352-2T were found to be closely related to Bacillus firmus NCIMB 9366T (98.2 % sequence similarity) and Bacillus cibi JG-30T (97.1 % sequence similarity), respectively. They also displayed low DNA–DNA reassociation values (less than 40 %) with respect to the most closely related Bacillus species. On the basis of their polyphasic characteristics, strain SMC 4352-1T and strain SMC 4352-2T represent two novel species of the genus Bacillus, for which the names Bacillus infantis sp. nov. (type strain SMC 4352-1T=KCCM 90025T=JCM 13438T) and Bacillus idriensis sp. nov. (type strain SMC 4352-2T=KCCM 90024T=JCM 13437T) are proposed.