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- Alsmark, Cecilia
(författare)
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Comparative Genomics of Obligate and Facultative Intracellular Parasites
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The α-proteobacteria Rickettsia prowazekii and Bartonella henselae are the causative agents of epidemic typhus and cat scratch disease respectively. Whereas R. prowazekii is an obligate intracellular parasite, B. henselae can live and proliferate both outside and inside the eukaryotic host cell. Besides the obvious medical interest to identify the complete gene set of two human pathogens, their genome sequences are also important for the study of evolutionary processes. Both R. prowazekii and B. henselae have small genomes, but their last common ancestor of these two bacteria was most likely a free-living organism with a substantially larger genome.The aim of this thesis is to compare the complete genomes of R. prowazekii and B. henselae and to decipher the evolutionary processes leading to the adaptation to an intracellular lifestyle. The working hypothesis was that the facultative intracellular B. henselae is an intermediate between a free living bacteria and the obligate R. prowazekii, which is corroborated. B. henselae has a broader biosynthetic repertoire than R. prowazekii, including the presence of genes for glycolysis and de novo biosynthesis of purines and pyrimidines. However, both bacteria have reduced gene sets for biosynthesis of amino acids and cofactors compared to free-living bacteria.Comparisons of gene order in bacteria reveal that several operons are well conserved between distantly related species. The genome sequences of R. prowazekii and B. henselae show that many of the operons that are usually conserved, are broken and rearranged in these species. One of the mechanisms of reductive evolution include intra-chromosomal recombination between repeated loci. This process expels one of the repeats and cause rearrangements in the gene order of the flanking regions. While the R. prowazekii genome almost completely lack repeated sequences, the B. henselae genome is rich in repeats. These repeats are, however, most often located within regions associated with pathogenicity islands. The higher number of scrambled operons, and the lower number of repeats, in R. prowazekii compared to B. henselae imply that the reductive process has gone further in the former species.
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| 2. |
- Holmberg, Martin, et al.
(författare)
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Evaluation of human seroreactivity to Bartonella species in Sweden
- 1999
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Ingår i: Journal of Clinical Microbiology. - 0095-1137 .- 1098-660X. ; 37:5, s. 1381-1384
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Tidskriftsartikel (refereegranskat)abstract
- Among the species that compose the expanding genus Bartonella, thus far only B. henselae and B. quintana have reportedly been isolated from humans in Europe. To evaluate the prevalence of Bartonella infection in Sweden,we conducted a retrospective serological examination of 126 human serum samples. These samples were analyzed for antibodies to B. henselae, B. quintana, and B. elizabethae, Serum samples from 100 blood donors, who spanned the ages of 20 to 60 and had no apparent clinical signs of illness, were also studied as a control group. An immunoglobulin G indirect fluorescence antibody assay revealed 4 and 8.3% Bartonella positivity rates for the blood donor and patient group, respectively, when a cutoff titer of greater than or equal to 64 was chosen. Among the blood donors, four were seropositive to B, elizabethae; one of these also had concordant positive titer to B. henselae, In the patient group, 14 serum samples were positive against Bartonella spp, These serum specimens represented nine patients. In three of these seropositive patients, paired serum samples displayed a fourfold increase in antibody titer to at least one of the three antigens, These three patients are discussed. In this report we also present a case study of a 60-year-old Swedish male with fatal myocarditis, Postmortem serological analysis revealed a high titer against B. elizabethae, PCR and nucleotide sequencing of the myocardial tissue from this patient, and of Liver tissue from one of the other three patients, showed sequences similar to B. quintana, The age, geographical origin, animal contacts, and serological response pattern to the different Bartonella antigens differed among the four patients. This study substantiates the presence of Bartonella spp, in Sweden, documents the seroreactivity to three Bartonella antigens in Swedish patients, and reports the first two cases of B. quintana-like infections in Sweden.
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