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- Möllenkvist, Andrea, et al.
(författare)
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The Moraxella catarrhalis immunoglobulin D-binding protein MID has conserved sequences and is regulated by a mechanism corresponding to phase variation
- 2003
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 185:7, s. 2285-2295
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of the Moraxella catarrhalis immunoglobulin D (IgD)-binding outer membrane protein MID and its gene was determined in 91 clinical isolates and in 7 culture collection strains. Eighty-four percent of the clinical Moraxella strains expressed MID-dependent IgD binding. The mid gene was detected in all strains as revealed by homology of the signal peptide sequence and a conserved area in the 3' end of the gene. When MID proteins from five different strains were compared, an identity of 65.3 to 85.0% and a similarity of 71.2 to 89.1% were detected. Gene analyses showed several amino acid repeat motifs in the open reading frames, and MID could be called a putative autotransport protein. Interestingly, homopolymeric [polyguanine [poly(G)]] tracts were detected at the 5' ends within the open reading frames. By flow cytometry, using human IgD and fluorescein isothiocyanate-conjugated anti-IgD polyclonal antibodies, most strains showed two peaks: one high- and one low-intensity peak. All isolates expressing high levels of MID had 1, 2, or 3 triplets of G's in their poly(G) tracts, while strains not expressing MID had 4, 7, 8, or 10 G's in their poly(G) tracts or point mutations causing a putative preterminated translation. Northern blot analysis revealed that the mid gene was regulated at the transcriptional level. Experiments with nonclumping variants of M. catarrhalis proved that bacteria lost their MID expression by removing a G in their poly(G) tracts. Moraxella strains isolated from the nasopharynx or from blood and sputum specimens expressed MID at approximately the same frequency. In addition, no variation was observed between strains of different geographical origins (Australia, Europe, Japan, or the United States). MID and the mid gene were found solely in M. catarrhalis, whereas related Neisseria and Moraxella species did not express MID. Taken together, MID appears to be a conserved protein that can be found in essentially all M. catarrhalis strains. Furthermore, MID is governed by poly(G) tracts when bacteria undergo phase variation.
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| 2. |
- Godhe, Anna, et al.
(författare)
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Polymerase chain reaction in detection of Gymnodinium mikimotoi and Alexandrium minutum in field samples from Southwest India
- 2001
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Ingår i: Marine Biotechnology. - 1436-2228 .- 1436-2236. ; 3:2, s. 152-162
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Tidskriftsartikel (refereegranskat)abstract
- Polymerase chain reaction (PCR) primers were constructed for the detection of two toxic dinoflagellate species, Gymnodinium mikimotoi and Alexandrium minutum. The primers amplified a product of expected size from cultured cells of G. mikimotoi and A. minutum. The species-specific primers targeting G. mikimotoi did not yield any product with a wide range of other cultured algae used as negative controls. Primers designed for A. minutum were species-group-specific since it PCR yielded a product from the closely related species A. ostenfeldii and A. andersonii, but not from other species of this genus tested. The confirmation of PCR products was performed by digestion of the products with restriction enzymes. Sensitivity analyses of the primers on DNA template from cultured cells was positive by PCR at a DNA template concentration of 1.5 x 10(-4) ng/microl (0.3 cells/L) for A. minutum, and at a DNA concentration of 2.5 x 10(-2) ng/microl (697 cells/L) for G. mikimotoi. The PCR method for detection of G. mikimotoi and A. minutum was applied on field samples collected with a plankton net. Gymnodinium mikimotoi could be detected in 11 field samples by microscopy, and all these field samples were positive by PCR. The cell counts of G. mikimotoi in simultaneously collected water samples ranged from 306 to 2077/L. Alexandrium minutum could be detected by microscopy in 3 different field samples. The cell counts in water samples collected at the same time as the net samples ranged from 115 to 1115 cells/L. Alexandrium minutum was detected by PCR in these field samples, with the exception of the sample displaying the lowest cell count (115 cells/L). Plankton samples that were negative by microscopy for any of the two target species were also negative by PCR. All the PCR products from field samples were confirmed by restriction enzyme digestion. The application of PCR-based detection of harmful algal bloom species for aquaculture and monitoring purposes in natural field samples is discussed.
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| 3. |
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| 4. |
- Svensson, Susanne, et al.
(författare)
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A case of consistent spatial differences in content of diarrhetic shellfish toxins (DST) among three bivalve species : Mytilus edulis, Ostrea edulis and Cerastoderma edule
- 2000
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Ingår i: Journal of Shellfish Research. - 0730-8000 .- 1943-6319. ; 19:2, s. 1017-1020
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Tidskriftsartikel (refereegranskat)abstract
- Content of diarrhetic .shellfi.sh toxins (DST) was compared among mussels (Mytilus edulis), oysters (Ostrea edulis). and cockles (Cercuioderma edule) at two spatial scales: regions (100 km apart) and locations within regions (5 km apart). Samples were analysed for DST using protein phosphatase inhibiton assay in individual digestive glands. Concentrations of DST in all oysters and cockles were below the detection limit in the assay, whereas mussels from both regions and all locations contained mean levels of DST above the regulation limit for harvest and marketing. Thus interspecific differences in content of DST were found along the Swedish west coast. Some behavioral and physiological phenomena are proposed to explain the differences among species. These include differential uptake and processing of toxic algae, biotransformation of toxins, and reduced filtration at low temperatures. These findings may have some implications for harvest and cultivation of bivalves and suggest a possibility that cockles and oysters could be marketed for human consumption during periods of elevated levels of DST in mussels.
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