| 1. |
- Valeur, Anders, et al.
(författare)
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Differences in lipid composition between free-living and initially adhered cells of a Gram-negative bacterium
- 1988
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Ingår i: Archives of Microbiology. - 0302-8933. ; 149:6, s. 521-526
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Tidskriftsartikel (refereegranskat)abstract
- The phospholipid fatty acid composition and poly-β-hydroxybutyrate (PHB) content of initially adhered and free-living cells of a Pseudomonas sp. isolated from the rape plant Brassica napus were examined with gas chromatography (GC). Five different adhesion experiments were made including variations in surface charge (hydrophilic and lipophilic), temperature, media composition and time of adhesion. Lipids and poly-β-hydroxybutyrate (PHB) were extracted with a chloroform-methanol-water mixture, hydrolyzed and esterified with pentafluorobenzyl bromide. Analysis was performed with capillary gas chromatography and flame ionization detection. A pronounced difference in both the ratio saturated/unsaturated fatty acids and in PHB content between free-living and adhered bacteria were found. The free-living bacteria has a significantly smaller ratio of saturated/unsaturated C16 and C18 fatty acids and also a smaller ratio of total C18/total C16 fatty acids. Bacteria adhered to the lipophilic surface had a higher ratio of saturated to unsaturated C16 fatty acids than at the hydrophilic surface. There were no major differences between the treatments regarding the amount of bacteria adhered to the surface or their lipid composition.
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| 2. |
- Gunnarsson, Torsten, et al.
(författare)
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Recycling of fecal pellets in isopods : Microorganisms and nitrogen compounds as potential food for Oniscus asellus L
- 1986
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 18:6, s. 595-600
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Tidskriftsartikel (refereegranskat)abstract
- The isopod Oniscus asellus was fed wood pieces. The fecal pellets produced during 6 days were reingested twice. Both fresh and ageing pellets were examined for microorganisms and nitrogen compounds including proteins and bacterial cell wall compounds, d-alanine and diaminopimelic acid. In old pellets, the plate counts of fungi decreased but that of bacteria as well as the concentrations of proteins and bacterial cell wall compounds increased from the first to the third gut passage. Immediately after a gut passage, the counts of microorganisms were lower than before the passage whereas the concentrations of bacterial cell wall compounds and proteins were higher. This indicates that both growth and lysis of bacteria occurred in the guts but that a considerable part of the bacterial cells were not digested and assimilated by the isopods. Comparison of the bacterial cell wall compounds also indicated shifts in the ratio of Gram-positive and Gram-negative bacteria during gut passages and during ageing of the fecal pellets. The concentration of total N did not markedly change after the second and third gut passages, indicating that the availability of N decreased due to accumulation of N into relatively recalcitrant proteins and bacterial cell walls.
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| 3. |
- Malmcrona-Friberg, Karin, et al.
(författare)
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Chemical changes in cell envelope and poly-β-hydroxybutyrate during short term starvation of a marine bacterial isolate
- 1986
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Ingår i: Archives of Microbiology. - 0302-8933. ; 144:4, s. 340-345
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Tidskriftsartikel (refereegranskat)abstract
- Qualitative and quantitative changes were observed in lipids, poly-β-hydroxybutyrate (PHB), and a cell wall peptidoglycan consitutent in a marine bacterial isolate during starvation for 24 h in an energy and nutrient-free medium. While the amount and composition of the membrane fatty acids fluctuated within the first hours of starvation, the total amount of fatty acids decreased during the starvation period. Furthermore, the ratio of monounsaturated to saturated fatty acids decreased and the proportion of short chain fatty acids increased. In the very early phase of starvation the bacteria contained PHB, which had been accumulated during the growth phase, but after 3 h no PHB was detected. Cells starved for phosphorus showed a different pattern as PHB was initially accumulated and did not decrease until 5 h of starvation. Synthesis of the cell wall amino acid d-alanine was initiated during the first phase of starvation. The effects of these changes on membrane fluidity and uptake of substrates as well as the use of fatty acids and PHB as energy resources during starvation are discussed.
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| 4. |
- Mårdén, Per, et al.
(författare)
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Physiological and morphological changes during short term starvation of marine bacterial islates
- 1985
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Ingår i: Archives of Microbiology. - 0302-8933. ; 142:4, s. 326-332
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Tidskriftsartikel (refereegranskat)abstract
- Three marine bacteria were examined for physiological and morphological changes in the initial phase of starvation. It was found that the starvation process was induced in a similar way irrespective of whether the cells were suspended in nutrient and energy free artificial seawater (NSS) or NSS supplemented with nitrogen and phosphorus. An initial phase of increased activity was consistent with a decreased response to added nutrients. Recovery from starvation exhibited the same response in both these starvation regimes, measured throughout the starvation period. Cells in nitrogen or phosphorus deprived starvation regimes, showed a high and rapid increased activity, followed by a delayed and more pronounced decline in respiratory activity. The initial phase of starvation also included a loss of poly-β-hydroybutyrate as observed by transmission electron microscopy (TEM). Two bacterial strains showed formation of small vesicles on the outer cell layer when examined by TEM. This formation and release of vesicles was related to the continuous size reduction during starvation survival. The results are discussed in terms of defining the mechanisms of initial cellular responses to nutrient deprivation.
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| 5. |
- Odham, Goran, et al.
(författare)
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Determination of microbial fatty acid profiles at femtomolar levels in human urine and the initial marine microfouling community by capillary gas chromatography-chemical ionization mass spectrometry with negative ion detection
- 1985
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Ingår i: Journal of Microbiological Methods. - : Elsevier BV. - 0167-7012. ; 3:5-6, s. 331-344
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Tidskriftsartikel (refereegranskat)abstract
- Room temperature esterification with the electron capturing pentafluorobenzyl bromide in glass capillaries, with analysis by capillary gas-liquid chromatography coupled with chemical ionization mass spectrometry and negative ion detection in the selected ion mode, allowed detection and identification of fatty acids from microbial biofilms at the femtomolar level. This sensitivity was achieved without loss of specificity of the mass spectrometric analysis. The detection of all the fatty acids commonly associated with bacteria was quantitative and linearly related to their concentration at a sensitivity permitting detection of about 600 bacteria the size of Escherichia coli. With this technique it was possible to detect the characteristic 3-hydroxy fatty acid of the lipopolysaccharide lipid A of E. coli infecting human urine at concentrations representing 10 4 bacteria and define the community structure of the initial marine microfouling community attached to a teflon surface at concentrations below the detectability by gas chromatography with flame ionization detection.
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| 6. |
- Tunlid, Anders, et al.
(författare)
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Determination of 13C-enrichment in bacterial fatty acids using chemical ionization mass spectrometry with negative ion detection
- 1987
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Ingår i: Journal of Microbiological Methods. - : Elsevier BV. - 0167-7012. ; 7:2-3, s. 77-89
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Tidskriftsartikel (refereegranskat)abstract
- Saturated, monoenoic and β-hydroxysubstituted fatty acids, 13C-labelled at the carboxyl group, were prepared from natural or synthetic unlabelled analogues. The synthetic route involves decarboxylation of the unlabelled fatty acid to the next lower iodide, displacement of iodide for [13C]cyanide and hydrolysis. The fatty acids were converted to their pentafluorobenzyl esters and analysed by selected ion monitorint using chemical ionization and negative ion detection. Measurements of the signal ratios for the negative carboxylate ion (m) and the (m + 1) ion showed that at 95% confidence level and n = 5, mean values differing by 1.0 atom% 13C will be significantly resolved. The calculated standard deviation was the same for the studied bacterial acids including the phospholipid ester-linked palmitoleic acid, β-hydroxymyristic acid in the lipopolysaccharides and β-hydroxybutyric acid in the storage polymer poly-β-hydroxyalkanoate. Sodium [1-13C]acetate or D-[13C6]glucose were pulse administered to a Gram-negative marine bacterium isolate. Phospholipid ester-linked fatty acids and β-hydroxybutyric acid showed extensive 13C-incorporation within 15 min after the pulse. After approximately 60 min a maximum of 10 atom% excess of 13C was reached for palmitoleic acid. The method provides the potential to measure the metabolic activity of bacterial communities by measuring the incorporation of 13C-labelled substrates into specific fatty acids that can be utilized as biomarkers for biomass, community structure and nutritional status.
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| 7. |
- Tunlid, Anders, et al.
(författare)
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Precision and sensitivity of the measurement of 15 N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry
- 1985
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Ingår i: Journal of Microbiological Methods. - 0167-7012. ; 3:3-4, s. 237-245
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Tidskriftsartikel (refereegranskat)abstract
- Sensitive detection of cellular components from specific groups of microbes can be utilized as 'signatures' in the examination of microbial consortia from soils, sediments or biofilms. Utilizing capillary gas chromatography/mass spectrometry and stereospecific derivatizing agents, D-alanine, a component localized in the prokaryotic (bacteria) cell wall, can be detected reproducibly. Enrichments of D- 15 N]alanine determined in E. coli grown with [ 15 N]ammonia can be determined with precision at 1.0 atom%. Chemical ionization with methane gas and the detection of negative ions (M-HF) - · and (M-F or M+H - HF) - formed from the heptafluorobutyryl D-2 butanol ester of D-alanine allowed as little as 8 pg (90 fmol) to be detected reproducibly. This method can be utilized to define the metabolic activity in terms of 15 N incorporation at the level of 10 3 -10 4 cells, as a function of the 15 N- 14 N ratio.
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