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Heterocystous cyanobacteria living within symbiosomes: genetic and physiological aspects
Kalmar University.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Kalmar: Högskolan i Kalmar , 2005. , 30 p.
Series
, Dissertation series / University of Kalmar, Faculty of Natural Science, ISSN 1650-2779 ; 20
Keyword [en]
Microbiology, cyanobacteria, plants, symbiosis, nitrogen-fixation
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:sh:diva-17116ISBN: 91-89584-42-2OAI: oai:DiVA.org:sh-17116DiVA: diva2:557916
Public defence
(English)
Opponent
Supervisors
Funder
Swedish Research Council
Available from: 2012-10-01 Created: 2012-10-01 Last updated: 2012-10-01Bibliographically approved
List of papers
1. Host specificity in the Richelia - diatom symbiosis revealed by hetR gene sequence analysis
Open this publication in new window or tab >>Host specificity in the Richelia - diatom symbiosis revealed by hetR gene sequence analysis
1999 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 1, no 5, 431-438 p.Article in journal (Refereed) Published
Abstract [en]

The filamentous heterocyst-forming cyanobacterium Richelia intracellularis forms associations with diatoms and is very abundant in tropical and subtropical seas. The genus Richelia contains only one species, R. intracellularis Schmidt, although it forms associations with several diatom genera and has considerable variation in size and morphology. The genetic diversity, and possible host specificity, within the genus Richelia is unknown. Using primers against hetR, a gene unique for filamentous cyanobacteria, specific polymerase chain reaction (PCR) products were obtained from natural populations of R. intracellularis filaments associated with three diatom genera. Phylogenetic analyses of these sequences showed that they were all in the same clade. This clade contained only the R. intracellularis sequences. The genetic affiliation of hetR sequences of R. intracellularis to those of other heterocystous cyanobacteria strongly suggests that it was not closely related to endosymbiotic Nostoc spp, hetR sequences. Sequences from R, intracellularis-Hemiaulus membranaceus sampled in the Atlantic and Pacific Oceans were almost identical, demonstrating that the genetic relatedness was not dependent on geographical location, All sequences displayed a deep divergence between symbionts from different genera and a high degree of host specificity.

National Category
Natural Sciences
Identifiers
urn:nbn:se:sh:diva-17126 (URN)000084962800009 ()
Funder
Swedish Research Council
Available from: 2012-10-01 Created: 2012-10-01 Last updated: 2012-10-01Bibliographically approved
2. Cloning and expression of a putative cyclodextrin glucosyltransferase from the symbiotically competent cyanobacterium Nostoc sp PCC 9229
Open this publication in new window or tab >>Cloning and expression of a putative cyclodextrin glucosyltransferase from the symbiotically competent cyanobacterium Nostoc sp PCC 9229
2003 (English)In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 219, no 2, 181-185 p.Article in journal (Refereed) Published
Abstract [en]

A polymerase chain reaction-based method was used to isolate a Nostoc sp. PCC 9229 cDNA from infected glands of Gunnera chilensis. The complete gene sequence was isolated from a genomic Nostoc sp. PCC 9229 library. Sequence analysis showed 84% amino acid similarity to a putative cyclodextrin glycosyltransferase from Nostoc sp. PCC 7120 and the gene was therefore termed cgt. Southern blot revealed that the cgt gene was present in symbiotically competent cyanobacteria. The cgt gene was expressed in free-living nitrogen-fixing cultures in light or in darkness when supplemented with fructose. This is the first expression analysis of a cgt gene from a cyanobacterium. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

National Category
Natural Sciences
Identifiers
urn:nbn:se:sh:diva-17124 (URN)10.1016/S0378-1097(02)1204-1 (DOI)000181567500005 ()
Funder
Swedish Research Council
Available from: 2012-10-01 Created: 2012-10-01 Last updated: 2012-10-01Bibliographically approved
3. The effect of exogenous carbohydrates on nitrogen fixation and hetR expression in Nostoc PCC 9229 forming symbiosis with Gunnera
Open this publication in new window or tab >>The effect of exogenous carbohydrates on nitrogen fixation and hetR expression in Nostoc PCC 9229 forming symbiosis with Gunnera
2000 (English)In: Symbiosis, ISSN 0334-5114, Vol. 28, no 1, 63-76 p.Article in journal (Refereed) Published
Abstract [en]

The cyanobacterium Nostoc PCC 9229 forms an intracellular nitrogen-fixing symbiosis with the angiosperm Gunnera. In symbiosis the cyanobacterium is enclosed in darkness and receives carbon from the plant in an unknown form. Out of five putative plant carbohydrate sources tested in vitro, fructose and glucose were found to support nitrogen fixation in darkness. The other three dextrin, sucrose and Gunnera sp. mucilage could not induce nitrogenase activity in darkness. The stimulatory effect by fructose was also observed in illuminated samples. After four weeks incubation in darkness, nitrogenase was still active in cultures when fructose was added and multiple thick-walled nitrogen-fixing cells (heterocysts) were observed, and chlorophyll levels unchanged. The expression as shown by Northern blot analysis revealed that fructose influenced the gene expression of hetR, a gene necessary for heterocyst formation, in darkness. Fructose and glucose may therefore be the carbohydrates supplied by the host plant to induce heterocyst differentiation and nitrogen fixation in the cyanobiont Nostoc PCC 9229.

Keyword
carbohydrates, hetR, N2-fixation, Nostoc, symbiosis
National Category
Natural Sciences
Identifiers
urn:nbn:se:sh:diva-17125 (URN)000086607100005 ()
Funder
Swedish Research Council
Available from: 2012-10-01 Created: 2012-10-01 Last updated: 2012-10-01Bibliographically approved
4. Sucrose synthase and glutamine synthetase expression in greenhouse cultivated Gunnera manicata forming symbiosis with Nostoc sp.
Open this publication in new window or tab >>Sucrose synthase and glutamine synthetase expression in greenhouse cultivated Gunnera manicata forming symbiosis with Nostoc sp.
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:sh:diva-17127 (URN)
Note

Som manuskript i avhandling. As manuscript in dissertation.

Available from: 2008-01-30 Created: 2012-10-01 Last updated: 2012-10-01Bibliographically approved

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