| 1. |
- Andersson, Jan O, et al.
(författare)
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Genomic rearrangements during evolution of the obligate intracellular parasite Rickettsia prowazekii as inferred from an analysis of 52015 bp nucleotide sequence
- 1997
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Ingår i: Microbiology. - 1350-0872 .- 1465-2080. ; 143:8, s. 2783-2795
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this study a description is given of the sequence and analysis of 52 kb from the 1.1 Mb genome of Rickettsia prowazekii, a member of the alpha-Proteobacteria. An investigation was made of nucleotide frequencies and amino acid composition patterns of 41 coding sequences, distributed in 10 genomic contigs, of which 32 were found to have putative homologues in the public databases. Overall, the coding content of the individual contigs ranged from 59 to 97%, with a mean of 81%. The genes putatively identified included genes involved in the biosynthesis of nucleotides, macromolecules and cell wall structures as well as citric acid cycle component genes. In addition, a putative identification was made of a member of the regulatory response family of two-component signal transduction systems as well as a gene encoding haemolysin. For one gene, the homologue of metK, an internal stop codon was discovered within a region that is otherwise highly conserved. Comparisons with the genomic structures of Escherichia coli, Haemophilus influenzae and Bacillus subtilis have revealed several atypical gene organization patterns in the R. prowazekii genome. For example, R. prowazekii was found to have a unique arrangement of genes upstream of dnaA in a region that is highly conserved among other microbial genomes and thought to represent the origin of replication of a primordial replicon. The results presented in this paper support the hypothesis that the R. prowazekii genome is a highly derived genome and provide examples of gene order structures that are unique for the Rickettsia.
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| 2. |
- Ausmees, Nora, et al.
(författare)
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Structural and putative regulatory genes involved in cellulose synthesis in Rhizobium leguminosarum bv. trifolii
- 1999
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 145, s. 1253-1262
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Tidskriftsartikel (refereegranskat)abstract
- Six genes involved in cellulose synthesis in Rhizobium leguminosarum bv. trifolii were identified using Tn5 mutagenesis. Four of them displayed homology to the previously cloned and sequenced Agrobacterium tumefaciens cellulose genes celA, celB, celC and celE. These genes are organized similarly in R. leguminosarum bv. trifolii. In addition, there were strong indications that two tandemly located genes, celR1 and celR2, probably organized as one operon, are involved in the regulation of cellulose synthesis. The deduced amino acid sequences of these genes displayed a high degree of similarity to the Caulobacter crescentus DivK and PleD proteins that belong to the family of two-component response regulators. This is to our knowledge the first report of genes involved in the regulation of cellulose synthesis. Results from attachment assays and electron microscopic studies indicated that cellulose synthesis in R. leguminosarum bv. trifolii is induced upon close contact with plant roots during the attachment process.
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| 3. |
- Backman, M, et al.
(författare)
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The phase-variable pilus-associated protein PilC is commonly expressed in clinical isolates of Neisseria gonorrhoeae, and shows sequence variability among strains
- 1998
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Ingår i: Microbiology (Reading, England). - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 144144 ( Pt 1), s. 149-156
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Tidskriftsartikel (refereegranskat)abstract
- Summary: PilC is a phase-variable protein associated with pilus-mediated adherence of pathogenic Neisseria to target cells. In this study, 24 strains of Neisseria gonorrhoeae with known epidemiological data were examined for expression of PilC. All strains produced PilC independently of serovar and site of isolation. To investigate whether the PilC protein is conserved or variable among gonococcal strains, the complete nucleotide sequence of pilC in four strains, isolated from either rectum, throat or blood, was determined. The deduced amino acid sequence in these strains differed from each other and from the two PilC proteins of N. gonorrhoeae MS11. These data demonstrate that PilC is commonly expressed, but the PilC sequence may vary among gonococcal strains.
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| 4. |
- Chalot, Michel, et al.
(författare)
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Kinetics, energetics and specificity of a general amino acid transporter from the ectomycorrhizal fungus Paxillus involutus
- 1996
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 142, s. 1749-1756
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics, energetics and specificity of a general amino acid transporter were studied in the ectomycorrhizal fungus Paxillus involutus (Batsch) Fr. The uptake of amino acids showed features characteristic of active transport. After correction for a non-mediated transport component, the kinetics of glutamate, glutamine, alanine and aspartate uptake measured over a wide concentration range followed the simple Michaelis-Menten saturation curves, The apparent K-m derived from the Eadie-Hofstee plots ranged from 7 mu M for alanine to 27 mu M for glutamate, Dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone and NaN3 strongly inhibited amino acid uptake, whereas dicyclohexylcarbodiimide. vanadate and the ionophores monensin and nonactin had no effect on the uptake. Both ph dependence and inhibition by protonophores are consistent with a proton symport mechanism for amino acid uptake by P. involutus, Competition studies indicated a broad substrate recognition by the uptake system, which resembles the general amino acid permease of yeast, Dixon plots of the inhibition of glutamate uptake by alanine, lysine and methionine sulfoximine showed that inhibitions were competitive, Tire physiological importance of this transporter for the exchange of nitrogenous compounds between fungal and host plant cells in ectomycorrhizal associations is discussed.
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| 5. |
- Johansson, Magnus, et al.
(författare)
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Transcription of the glnB and glnA genes in the photosynthetic bacterium Rhodospirillum rubrum
- 1996
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 142 ( Pt 5), s. 1265-1272
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Tidskriftsartikel (refereegranskat)abstract
- The PII protein, encoded by glnB, has a central role in the control of nitrogen metabolism in nitrogen-fixing prokaryotes. The glnB gene of Rhodospirillum rubrum was isolated and sequenced. The deduced amino acid sequence had very high sequence identity to other PII proteins. The glnA gene, encoding glutamine synthetase, was located 135 bp downstream of glnB and was partially sequenced. glnB is cotranscribed with glnA from a promoter with high similarity to the sigma 54-dependent promoter consensus sequence. A putative sigma 70 promoter was also identified further upstream of glnB. Northern blotting analyses showed that in addition glnA is either transcribed from an unidentified promoter or, more likely, that the glnBA transcript is processed to give the glnA mRNA. The total level of the two transcripts was much higher in nitrogen-fixing cells than in ammonia-grown cells.
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| 6. |
- Johansson, Per, et al.
(författare)
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Organisation of genes for tetrapyrrole biosynthesis in Gram-positive bacteria
- 1999
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 154, s. 529-538
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Tidskriftsartikel (refereegranskat)abstract
- Clusters of genes encoding enzymes for tetrapyrrole biosynthesis were cloned from Bacillus sphaericus, Bacillus stearothermophilus, Brevibacillus brevis and Paenibacillus macerans. The sequences of all hemX genes found, and of a 6.3 kbp hem gene cluster from P. macerans, were determined. The structure of the hem gene clusters was compared to that of other Gram-positive bacteria. The Bacillus and Brevibacillus species have a conserved organization of the genes hemAXCDBL, required for biosynthesis of uroporphyrinogen III (UroIII) from glutamyl-tRNA. In P. macerans, the hem genes for UroIII synthesis are also closely linked but their organization is different: there is no hemX gene and the gene cluster also contains genes, cysC(B) and cysG(A)-hemD, encoding the enzymes required for synthesis of sirohaem from UroIII. Bacillus subtilis contains genes for three proteins, NasF, YlnD and YlnF, with sequence similarity to Escherichia coli CysG, which is a multi-functional protein catalysing sirohaem synthesis from UroIII. It is shown that YlnF is required for sirohaem synthesis and probably catalyses the precorrin-2 to sirohaem conversion. YlnD probably catalyses precorrin-2 synthesis from UroIII and NasF seems to be specific for nitrite reduction.
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| 7. |
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| 8. |
- Jonsson, Maria, et al.
(författare)
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Transcriptional and translational regulation of the expression of the major outer surface proteins in Lyme disease Borrelia strains
- 1995
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Ingår i: Microbiology. - : Society for General Microbiology. - 1350-0872 .- 1465-2080. ; 141:6, s. 1321-1329
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Tidskriftsartikel (refereegranskat)abstract
- The major outer surface proteins of Lyme disease spirochaetes are differentially expressed in different isolates. Borrelia afzelii strain F1 expresses none, or very low amounts, of the OspA and OspB proteins. To elucidate the mechanisms that control the expression of these abundant surface proteins the ospAB operon of B. afzelii F1 was cloned, sequenced and compared to the previously sequenced ospAB operon of B. afzelii ACAI and Borrelia burgdorferi B31. The two B. afzelii strains showed almost 100% identity at the DNA level, although Coomassie-stained gels and Western blot analyses showed significant variation in the Osp protein content. Transcriptional analysis revealed that the amount of ospAB mRNA produced in B. afzelii F1 varies more than the amount of protein, suggesting that the expression of OspA and OspB proteins is regulated at both the transcriptional and the translational level. Furthermore, the inverse relationship between the transcription of ospC and the ospAB operon could indicate coregulation of these separately encoded operons.
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| 9. |
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| 10. |
- Meinander, N, et al.
(författare)
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A heterologous reductase affects the redox balance of recombinant Saccharomyces cerevisiae
- 1996
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 142, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- Recombinant Saccharomyces cerevisiae harbouring the xylose reductase (XR) gene XYL1 from Pichia stipitis was grown in anoxic chemostat culture at two different dilution rates. At each dilution rate a transient experiment, encompassing a shift in the sugar content of the medium from glucose to glucose plus xylose was performed. The steady states at the beginning and the end of the transients were compared in terms of specific product fluxes from glucose metabolism. At both dilution rates, the specific glycerol flux decreased and the specific acetate and CO2 fluxes increased. The specific ethanol flux was not affected. At the lower dilution rate, the production of biomass decreased during the transient, but at the higher dilution rate it increased. The changes in product pattern can be explained as being due to the redox perturbation caused by the consumption of reduced cofactors in the XR-catalysed reaction. Regeneration of NAD partly through xylose reduction instead of glycerol production decreased the formation of glycerol. Additionally, xylose reduction activated those pathways which produce reduced cofactors, such as acetate formation and the pentose phosphate pathway, indicated by increased acetate and CO, production. The dual cofactor specificity of XR, with a preference for NADPH over NADH, was evident from the effects of xylose reduction on product fluxes. Comparison of the xylose reduction rates at low and high glucose flux indicated that the supply of reduced cofactors partly controlled the reaction rate. At the higher dilution rate, control by some other factor such as xylose transport or XR activity increased. Calculation of carbon balances at the steady states showed that all substrate carbon was recovered in biomass or products. Based on the specific product fluxes, calculations of quantitative cofactor balances at the steady states was attempted. However, sensitivity calculations showed that analysis errors in the range of 5% caused substantial errors in the cofactor balance, without affecting the carbon balance.
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