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- Andersson, Jan O, et al.
(författare)
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A century of typhus, lice and Rickettsia
- 2000
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Ingår i: Research in Microbiology. - : EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER. - 0923-2508 .- 1769-7123. ; 151:2, s. 143-150
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Tidskriftsartikel (refereegranskat)abstract
- At the beginning of the 20th century, it was discovered at the Pasteur Institute in Tunis that epidemic typhus is transmitted by the human body louse. The complete genome sequence of its causative agent, Rickettsia prowazekii, was determined at Uppsala University in Sweden at the end of the century. In this mini-review, we discuss insights gained from the genome sequence of this fascinating and deadly organism.
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| 2. |
- Naumov, Gennadi I., et al.
(författare)
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Genetic characterization of the nonconventional yeast Hansenula anomala
- 2001
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Ingår i: Research in Microbiology. - : Elsevier. - 0923-2508 .- 1769-7123. ; 152:6, s. 551-562
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Tidskriftsartikel (refereegranskat)abstract
- We describe genetic, molecular and taxonomic characteristics of the yeast Hansenula anomala. Pulsed-field gel electrophoresis of chromosomal DNAs from 19 H. anomala strains and related species indicated that H. anomala had a clearly different karyotype. Chromosome length polymorphism of the H. anomala strains was independent of their geographic origin and source of isolation. The strains were classified into four groups of similar karyotypes and one strain showed a unique profile. The sizes of chromosomes ranged from 850 to 3500 kb in different strains. The haploid chromosome number of H. anomala is at least nine. We have found RAPD primers discriminating at both the species and strain levels. All the primers tested except the M13 core sequence generated unique patterns with most strains. The results indicate the usefulness of PCR analysis with primer M13 for identification of the H. anomala species. Screening of the CBS (Utrecht) collection strains of H. anomala showed that they are rather difficult objects for genetic hybridization analysis. The strains have low fertility, viz. very poor sporulation, low mating type activities and, as a rule, nonviable ascospores. The majority of the hybrids obtained are polyploid, probably tetraploid, as judged by the segregation of control auxotrophic markers. Nevertheless, some monosporic cultures of the strains studied, including the biocontrol yeast J121, formed diploid hybrids with regular meiotic segregation of control auxotrophic markers. As a rule, H. anomala isolates are homothallic, showing delayed self-diploidization. Rare stable heterothallic strains of H. anomala also occur.
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| 3. |
- Maisnier-Patin, Sophie, et al.
(författare)
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Adaptation to the deleterious effects of antimicrobial drug resistance mutations by compensatory evolution
- 2004
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 155:5, s. 360-369
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Tidskriftsartikel (refereegranskat)abstract
- Compensatory mutations, due to their ability to mask the deleterious effects of another mutation, are important for the adaptation and evolution of most organisms. Resistance to antibiotics, antivirals, antifungals, herbicides and insecticides is usually associated with a fitness cost. As a result of compensatory evolution, the initial fitness costs conferred by resistance mutations (or other deleterious mutations) can often be rapidly and efficiently reduced. Such compensatory evolution is potentially of importance for (i) the long-term persistence of drug resistance, (ii) reducing the rate of fitness loss associated with the accumulation of deleterious mutations in small asexual populations, and (iii) the evolution of complexity of cellular processes.
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| 4. |
- Roth, John R, et al.
(författare)
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Amplification-mutagenesis : how growth under selection contributes to the origin of genetic diversity and explains the phenomenon of adaptive mutation
- 2004
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 155:5, s. 342-351
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of a particular bacterial genetic system has been interpreted as evidence that selective stress induces general mutagenesis or even preferentially directs mutations to sites that improve growth (adaptive mutation). It has been proposed that changes in mutability are a programmed response to stress in non-growing cells. In contrast, the amplification-mutagenesis model suggests that stress has no direct effect on the mutation rate and that mutations arise in cells growing under strong selection. In this model, stress serves only as a selective pressure that favors cells with multiple copies of a growth-limiting gene. Mutations are made more probable because more target copies are added to the selection plate-more cells with more mutational targets per cell. The amplification-mutagenesis process involves standard genetic events and therefore should apply to all biological systems. Idiosyncrasies of the particular system described here accelerate this process, allowing an evolutionary series of events to be completed in only a few days.
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