| 1. |
- Graells, Tiscar, et al.
(författare)
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Legionella pneumophila recurrently isolated in a Spanish hospital : Two years of antimicrobial resistance surveillance
- 2018
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Ingår i: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 166, s. 638-646
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim of this study was to monitor the spread, persistence and antibiotic resistance patterns of Legionella spp. strains found in a hospital water distribution system. These environmental studies are intended to help detect the presence of antibiotic resistant strains before they infect patients.METHODS: Antimicrobial surveillance tests were performed at 27 different sampling points of the water network of a large Spanish hospital over two years. Water samples were screened for Legionella according to ISO 11731:2007. Legionella spp. isolates were identified by serotyping and by mass spectrometry (MALDI-ToF). Epidemiological molecular typing was done by Pulse-Field Gel Electrophoresis (PFGE) and by Sequence-Based Typing (SBT). Antibiotic susceptibility tests were performed using disk diffusion and ETEST®.RESULTS: Legionella spp. were recurrently isolated for 2 years. All isolates belonged the same group, L. pneumophila serogroups 2-14. Isolates were all attributed by SBT to sequence type (ST) ST328, although PFGE revealed 5 different patterns. No significant change in antibiotic susceptibility could be observed for this study period, irrespectively of the method used.CONCLUSION: Colonization of water systems by Legionella spp. is still occurring, although all the prevention rules were strictly followed. Antibiotic resistance monitoring may help us to find resistance in bacteria with environmental reservoirs but difficult to isolate from patients. The knowledge of the antibiotic susceptibility in environmental strains may help us to predict changes in clinical strains. This study might also help reconsidering Legionnaires' disease (LD) diagnostic methods. L. pneumophila serogroups 2-14 present all along the time of the investigation in the water distribution system can cause LD. However, they may not be detected by routine urine tests run on patients, thereby missing an ongoing LD infection.
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| 2. |
- Graells, Tiscar, et al.
(författare)
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The all-intracellular order Legionellales is unexpectedly diverse, globally distributed and lowly abundant.
- 2018
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press. - 0168-6496 .- 1574-6941. ; 94:12
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Tidskriftsartikel (refereegranskat)abstract
- Legionellales is an order of the Gammaproteobacteria, only composed of host-adapted, intracellular bacteria, including the accidental human pathogens Legionella pneumophila and Coxiella burnetii. Although the diversity in terms of lifestyle is large across the order, only a few genera have been sequenced, owing to the difficulty to grow intracellular bacteria in pure culture. In particular, we know little about their global distribution and abundance.Here, we analyze 16/18S rDNA amplicons both from tens of thousands of published studies and from two separate sampling campaigns in and around ponds and in a silver mine. We demonstrate that the diversity of the order is much larger than previously thought, with over 450 uncultured genera. We show that Legionellales are found in about half of the samples from freshwater, soil and marine environments, and quasi-ubiquitous in man-made environments. Their abundance is low, typically 0.1%, with few samples up to 1%. Most Legionellales OTUs are globally distributed, while many do not belong to a previously identified species.This study sheds a new light on the ubiquity and diversity of one major group of host-adapted bacteria. It also emphasizes the need to use metagenomics to better understand the role of host-adapted bacteria in all environments.
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| 3. |
- Lind, Anders E., et al.
(författare)
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Genomes of two archaeal endosymbionts show convergent adaptations to an intracellular lifestyle.
- 2018
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 12:11, s. 2655-2667
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Tidskriftsartikel (refereegranskat)abstract
- Endosymbiosis is a widespread phenomenon in the microbial world and can be based on diverse interactions between endosymbiont and host cell. The vast majority of the known endosymbiotic interactions involve bacteria that have invaded eukaryotic host cells. However, methanogenic archaea have been found to thrive in anaerobic, hydrogenosome-containing protists and it was suggested that this symbiosis is based on the transfer of hydrogen. Here, we used culture-independent genomics approaches to sequence the genomes of two distantly related methanogenic endosymbionts that have been acquired in two independent events by closely related anaerobic ciliate hosts Nyctotherus ovalis and Metopus contortus, respectively. The sequences obtained were then validated as originating from the ciliate endosymbionts by in situ probing experiments. Comparative analyses of these genomes and their closest free-living counterparts reveal that the genomes of both endosymbionts are in an early stage of adaptation towards endosymbiosis as evidenced by the large number of genes undergoing pseudogenization. For instance, the observed loss of genes involved in amino acid biosynthesis in both endosymbiont genomes indicates that the endosymbionts rely on their hosts for obtaining several essential nutrients. Furthermore, the endosymbionts appear to have gained significant amounts of genes of potentially secreted proteins, providing targets for future studies aiming to elucidate possible mechanisms underpinning host-interactions. Altogether, our results provide the first genomic insights into prokaryotic endosymbioses from the archaeal domain of life.
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| 4. |
- Martijn, Joran, et al.
(författare)
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Deep mitochondrial origin outside the sampled alphaproteobacteria
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 557:7703, s. 101-105
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria are ATP-generating organelles, the endosymbiotic origin of which was a key event in the evolution of eukaryotic cells(1). Despite strong phylogenetic evidence that mitochondria had an alphaproteobacterial ancestry(2), efforts to pinpoint their closest relatives among sampled alphaproteobacteria have generated conflicting results, complicating detailed inferences about the identity and nature of the mitochondrial ancestor. While most studies support the idea that mitochondria evolved from an ancestor related to Rickettsiales(3-9), an order that includes several host-associated pathogenic and endosymbiotic lineages(10,11), others have suggested that mitochondria evolved from a free-living group(12-14). Here we re-evaluate the phylogenetic placement of mitochondria. We used genome-resolved binning of oceanic metagenome datasets and increased the genomic sampling of Alphaproteobacteria with twelve divergent clades, and one clade representing a sister group to all Alphaproteobacteria. Subsequent phylogenomic analyses that specifically address long branch attraction and compositional bias artefacts suggest that mitochondria did not evolve from Rickettsiales or any other currently recognized alphaproteobacterial lineage. Rather, our analyses indicate that mitochondria evolved from a proteobacterial lineage that branched off before the divergence of all sampled alphaproteobacteria. In light of this new result, previous hypotheses on the nature of the mitochondrial ancestor(6,15,16) should be re-evaluated.
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| 5. |
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| 6. |
- Tamarit, Daniel, 1988-, et al.
(författare)
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Origin and evolution of the Bartonella Gene Transfer Agent
- 2018
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Ingår i: Molecular biology and evolution. - : Oxford University Press. - 0737-4038 .- 1537-1719. ; 35:2, s. 451-464
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Tidskriftsartikel (refereegranskat)abstract
- Gene transfer agents (GTAs) are domesticated bacteriophages that have evolved into molecular machines for the transferof bacterial DNA. Despite their widespread nature and their biological implications, the mechanisms and selective forcesthat drive the emergence of GTAs are still poorly understood. Two GTAs have been identifiedintheAlphaproteobacteria:the RcGTA, which is widely distributed in a broad range of species; and the BaGTA, which has a restricted host range thatincludes vector-borne intracellular bacteria of the genusBartonella. The RcGTA packages chromosomal DNA randomly,whereas the BaGTA particles contain a relatively higher fraction of genes for host interaction factors that are amplifiedfrom a nearby phage-derived origin of replication. In this study, we compare the BaGTA genes with homologous bac-teriophage genes identified in the genomes ofBartonellaspecies and close relatives. Unlike the BaGTA, the prophagegenes are neither present in all species, nor inserted into homologous genomic sites. Phylogenetic inferences and sub-stitution frequency analyses confirm codivergence of the BaGTA with the host genome, as opposed to multiple integra-tion and recombination events in the prophages. Furthermore, the organizationof segments flanking the BaGTA differsfrom that of the prophages by a few rearrangement events,which have abolished the normal coordination betweenphage genome replication and phage gene expression. Based on the results of our comparative analysis, we propose amodel for how a prophage may be transformed into a GTA that transfers amplified bacterial DNA segments.
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