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Birgitta Bergman

Publications and source records attributed to Birgitta Bergman.

16 recordsLinked to original sources
PubMed2006

FtsZ may have dual roles in the filamentous cyanobacterium Nostoc/Anabaena sp. strain PCC 7120.

The cellular and subcellular localization of FtsZ, a bacterial cell division protein, were investigated in vegetative cells of the filamentous cyanobacterium Nostoc/Anabaena sp. strain PCC 7120. We show by using immunogold-transmission electron microscopy that FtsZ forms a ring structure in a filamentous cyanobacterium, similar to observations in unicellular bacteria and chloroplasts. This finding, that the FtsZ in a filamentous cyanobacterium accumulates at the growing edge of the division septa leading to the formation of the typical prokaryotic Z-ring arrangement, is novel. Moreover, an apparent cytoplasmic distribution of FtsZ occurred in vegetative cells. During the transition of vegetative cells into terminally differentiated heterocysts the cytoplasmic FtsZ levels decreased substantially. These findings suggest a conserved function of FtsZ among prokaryotes, including filamentous cyanobacteria with cell differentiation capacity, and possibly a role of FtsZ as a cytoskeletal component in the cytoplasm.

Bacterial Proteins↗
PubMed2006

Protein expression profiles in an endosymbiotic cyanobacterium revealed by a proteomic approach.

Molecular mechanisms behind adaptations in the cyanobacterium (Nostoc sp.) to a life in endosymbiosis with plants are still not clarified, nor are the interactions between the partners. To get further insights, the proteome of a Nostoc strain, freshly isolated from the symbiotic gland tissue of the angiosperm Gunnera manicata Linden, was analyzed and compared with the proteome of the same strain when free-living. Extracted proteins were separated by two-dimensional gel electrophoresis and were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry combined with tandem mass spectrometry. Even when the higher percentage of differentiated cells (heterocysts) in symbiosis was compensated for, the majority of the proteins detected in the symbiotic cyanobacteria were present in the free-living counterpart, indicating that most cellular processes were common for both stages. However, differential expression profiling revealed a significant number of proteins to be down-regulated or missing in the symbiotic stage, while others were more abundant or only expressed in symbiosis. The differential protein expression was primarily connected to i) cell envelope-associated processes, including proteins involved in exopolysaccharide synthesis and surface and membrane associated proteins, ii) to changes in growth and metabolic activities (C and N), including upregulation of nitrogenase and proteins involved in the oxidative pentose phosphate pathway and downregulation of Calvin cycle enzymes, and iii) to the dark, microaerobic conditions offered inside the Gunnera gland cells, including changes in relative phycobiliprotein concentrations. This is the first comprehensive analysis of proteins in the symbiotic state.

Bacterial Proteins↗
PubMed2006

Cyanobacterial chemotaxis to extracts of host and nonhost plants.

Chemotaxis may be important when forming cyanobacterial symbioses. However, knowledge of cyanobacterial attraction towards plants and factors affecting chemotaxis is limited. Chemo-attraction was observed in Nostoc strains 8964:3 and PCC 73102 towards exudate or crushed extract of the natural hosts Gunnera manicata, Cycas revoluta and Blasia pusilla, and the nonhost plants Trifolium repens, Arabidopsis thaliana and Oryza sativa. As all tested plant extracts generated chemotaxis, the possibility to attract cyanobacteria may be widespread in plants. Chemotaxis was reduced by increased temperature and darkness and was stimulated by phosphorous and iron starvation and elevated salt concentration. Sugars (arabinose, galactose, and glucose) had a positive effect on chemotaxis, whereas flavonoids (chrysin and naringenin) and amino acids (methionine, glycine, serine, phenylalanine, glutamine, and lysine) had no effect.

Arabidopsis↗
PubMed2006

Phosphorus-limited growth dynamics in two Baltic Sea cyanobacteria, Nodularia sp. and Aphanizomenon sp.

Rates of carbon (C) specific growth and nitrogen (N2) fixation were monitored in cultures of Baltic Sea Nodularia and Aphanizomenon exposed to gradual limitation by inorganic phosphorus (P). Both cyanobacteria responded by decreased cellular P content followed by lowered rates of growth and N2 fixation. C-specific growth and cellular N content changed faster in Aphanizomenon both when inorganic P was lowered as well as during reintroduction of P. Aphanizomenon also showed a more rapid increase in N-specific N2 fixation associated with increased C-specific growth. When ambient concentrations of inorganic P declined, both cyanobacteria displayed higher rates of alkaline phosphatase (APase) activity. Lower substrate half-saturation constants (KM) and higher Vmax : KM ratio of the APase enzyme associated with Nodularia suggest a higher affinity for dissolved organic P (DOP) substrate than Aphanizomenon. Aphanizomenon, which appears more sensitive to changes in ambient dissolved inorganic P, may be adapted to environments with elevated concentrations of P or repeated intrusions of nutrient-rich water. Nodularia on the other hand, with its higher tolerance to increased P starvation may have an ecological advantage in stratified surface waters of the Baltic Sea during periods of low P availability.

Aphanizomenon↗
PubMed2005

Diverse taxa of cyanobacteria produce beta-N-methylamino-L-alanine, a neurotoxic amino acid.

Cyanobacteria can generate molecules hazardous to human health, but production of the known cyanotoxins is taxonomically sporadic. For example, members of a few genera produce hepatotoxic microcystins, whereas production of hepatotoxic nodularins appears to be limited to a single genus. Production of known neurotoxins has also been considered phylogenetically unpredictable. We report here that a single neurotoxin, beta-N-methylamino-L-alanine, may be produced by all known groups of cyanobacteria, including cyanobacterial symbionts and free-living cyanobacteria. The ubiquity of cyanobacteria in terrestrial, as well as freshwater, brackish, and marine environments, suggests a potential for wide-spread human exposure.

Amino Acids, Diamino↗
PubMed2005

Competition among symbiotic cyanobacterial Nostoc strains forming artificial associations with rice (Oryza sativa).

Competition among four symbiotically competent Nostoc strains, colonizing rice roots, was examined using hetR-DGGE (denaturing gradient gel electrophoresis) as strain identification. Although mixed in various combinations, only one strain at a time associated with the rice roots. Nostoc strain 8964:3 was the most competitive and our data suggest that its competitive fitness was dependent on rapid hormogonial spreading as displayed on agar plates. Furthermore, rice roots induced hormogonia in all tested Nostoc strains, but only Nostoc strain 9104 showed positive chemotaxis towards the root. Inhibition of growth of competing cyanobacterial strains was not apparent.

Chemotaxis↗
PubMed2005

Unveiling of novel radiations within Trichodesmium cluster by hetR gene sequence analysis.

The filamentous nonheterocystous cyanobacterial genus Katagnymene is a common diazotrophic component of tropical and subtropical oceans. To assess the phylogenetic affiliation of this taxon, two partial 16S rRNA gene sequences and 25 partial hetR gene sequences originating from the genera Katagnymene and Trichodesmium collected from open, surface waters of the Atlantic, Indian, and Pacific oceans were compared. Single trichomes or colonies were identified morphologically by using light microscopy and then used directly as templates in hetR PCR analyses. In addition, three cultured strains, identified as Katagnymene pelagica, Katagnymene spiralis, and Trichodesmium sp., were examined. The data show that the genus Katagnymene is in the Trichodesmium cluster and that K. pelagica Lemmermann and K. spiralis Lemmermann are most likely one species, despite their different morphologies. Phylogenetic analyses also unveiled four distinct clusters in the Trichodesmium cluster, including one novel cluster. Our findings emphasize the conclusion that known morphological traits used to differentiate marine nonheterocystous cyanobacteria at the genus and species levels correlate poorly with genetic data, and a revision is therefore suggested.

Bacterial Proteins↗
PubMed2004

Mutagenesis of the cysteine residues in the transcription factor NtcA from Anabaena PCC 7120 and its effects on DNA binding in vitro.

NtcA is a transcription factor found in a wide variety of cyanobacteria. It is a key component in the control of the nitrogen metabolism, and regulates genes involved in ammonia assimilation, heterocyst differentiation and nitrogen fixation. NtcA expression is subject to nitrogen control, but there is also evidence that the binding of NtcA to DNA can be regulated by a redox mechanism involving the two cysteine residues in the NtcA protein from Anabaena PCC 7120. In order to investigate this further, the two cysteine residues in NtcA were mutated into alanine to give four variants of the protein: wild-type NtcA, the point-mutated variants Cys157Ala and Cys164Ala, as well as the double mutant Cys157Ala/Cys164Ala. The binding of a DNA probe containing a palindromic NtcA-binding motif was investigated by gel mobility shift analysis under non-reducing and reducing conditions. The experiments show that the DNA binding in vitro is stronger in the presence of the reducing agent DTT than in its absence. However, this effect is not due to breaking of a disulfide bond between the cysteine residues, since the double mutant containing no cysteines was also affected by DTT. A molecular model of a monomer of NtcA, based on the homologous cAMP receptor protein structure, was created in order to locate the positions of the cysteine residues. The NtcA model suggested that the positions of the sulfur atoms are not compatible with formation of a bond between them.

Anabaena↗
PubMed2004

Expression of cyanobacterial genes involved in heterocyst differentiation and dinitrogen fixation along a plant symbiosis development profile.

Members of the cyanobiont genus Nostoc, forming an endosymbiosis with members of the angiosperm genus Gunnera, undergo a number of characteristic phenotypic changes during the development of the symbiosis, the genetic background of which is largely unknown. Transcription patterns of genes related to heterocyst differentiation and dinitrogen fixation and corresponding protein profiles were examined, using reverse transcription-polymerase chain reaction and Western blots, along a developmental (apex to mature parts) sequence in Gunnera magellanica and G. manicata and under mimicked symbiotic conditions in a free-living Gunnera isolate (Nostoc strain 0102). The hetR gene was highly expressed and correlated positively with an increase in heterocyst frequency and with ntcA expression, whereas nifH expression was already high close to the growing apex and glnB (P(II)) expression decreased along the symbiotic profile. Although gene expression appeared to be regulated to a large extent in the same fashion as in free-living cyanobacteria, significant differences were apparent, such as the overexpression of both hetR and ntcA and the contrasting down-regulation of glnB, features indicating important regulatory differences between symbiotic and free-living cyanobacteria. The significance of these findings is discussed in a symbiotic context.

Bacterial Proteins↗
PubMed2004

Ocular changes, risk markers for eye disorders and effects of cataract surgery in elderly people: a study of an urban Swedish population followed from 70 to 97 years of age.

AIMS: To investigate the prevalence of and potential risk factors for ocular disorders and the effects of timing of cataract surgery from age 70-97 years. POPULATION: A representative population sample taken from within the Gerontological and Geriatric Population Studies (H 70) in Gothenburg, Sweden (n = 958). All subjects underwent eye examinations at age 70 years in 1971 and subsequently at ages 82, 88, 95 and 97 years. All inhabitants of Gothenburg aged 95 and 97 years were invited to participate in the study. RESULTS: Decreased vision (visual acuity < or = 0.5) was found in 20% and 80% of subjects at ages 82 and 97 years, respectively. Blood folate and physical activity at age 70 years correlated positively and body mass index (BMI) negatively to visual acuity (VA) > or = 0.8 at ages 82 and 88 years. Smoking at age 70 years correlated to early age-related maculopathy (ARM). Cataract surgery had been performed in 40% of subjects at age 97 years. Surgery 2 years earlier led to a 15% increase in time spent with improved vision. CONCLUSIONS: The deterioration of vision in elderly people is a major health problem, for which 'low' folate status, smoking, 'high' BMI and low physical activity are potential risk factors. Early cataract surgery is also beneficial in very old patients.

Aged↗
PubMed2004

N2 fixation by unicellular bacterioplankton from the Atlantic and Pacific oceans: phylogeny and in situ rates.

N2-fixing proteobacteria (alpha and gamma) and unicellular cyanobacteria are common in both the tropical North Atlantic and Pacific oceans. In near-surface waters proteobacterial nifH transcripts were present during both night and day while unicellular cyanobacterial nifH transcripts were present during the nighttime only, suggesting separation of N2 fixation and photosynthesis by unicellular cyanobacteria. Phylogenetic relationships among unicellular cyanobacteria from both oceans were determined after sequencing of a conserved region of 16S ribosomal DNA (rDNA) of cyanobacteria, and results showed that they clustered together, regardless of the ocean of origin. However, sequencing of nifH transcripts of unicellular cyanobacteria from both oceans showed that they clustered separately. This suggests that unicellular cyanobacteria from the tropical North Atlantic and subtropical North Pacific share a common ancestry (16S rDNA) and that potential unicellular N2 fixers have diverged (nifH). N2 fixation rates for unicellular bacterioplankton (including small cyanobacteria) from both oceans were determined in situ according to the acetylene reduction and 15N2 protocols. The results showed that rates of fixation by bacterioplankton can be almost as high as those of fixation by the colonial N2-fixing marine cyanobacteria Trichodesmium spp. in the tropical North Atlantic but that rates are much lower in the subtropical North Pacific.

Animals↗
PubMed2003

Cloning and expression of a putative cyclodextrin glucosyltransferase from the symbiotically competent cyanobacterium Nostoc sp. PCC 9229.

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.

Blotting, Northern↗
PubMed2002

Evidence for production of the phytohormone indole-3-acetic acid by cyanobacteria.

The ability of cyanobacteria to produce the phytohormone indole-3-acetic acid (IAA) was demonstrated. A colorimetric (Salkowski) screening of 34 free-living and symbiotically competent cyanobacteria, that represent all morphotypes from the unicellular to the highly differentiated, showed that auxin-like compounds were released by about 38% of the free-living as compared to 83% of the symbiotic isolates. The endogenous accumulation and release of IAA were confirmed immunologically (ELISA) using an anti-IAA antibody on 10 of the Salkowski-positive strains, and the chemical authenticity of IAA was further verified by chemical characterization using gas chromatography-mass spectrometry in Nostoc PCC 9229 (isolated from the angiosperm Gunnera) and in Nostoc 268 (free-living). Addition of the putative IAA precursor tryptophan enhanced IAA accumulation in cell extracts and supernatants. As the genome of the symbiotically competent Nostoc PCC 73102 contains homologues of key enzymes of the indole-3-pyruvic acid pathway, a transaminase and indolepyruvate decarboxylase (IpdC), the putative ipdC gene from this cyanobacterium was cloned and used in Southern blot analysis. Out of 11 cyanobacterial strains responding positively in the Salkowski/ELISA test, ipdC homologues were found in 4. A constitutive and possibly tryptophan-dependent production of IAA via the indole-3-pyruvic acid pathway is therefore suggested. The possible role of IAA in cyanobacteria in general and in their interactions with plants is discussed.

Amino Acid Sequence↗
PubMed2002

A longitudinal study of visual acuity and visual rehabilitation needs in an urban Swedish population followed from the ages of 70 to 97 years of age.

PURPOSE: To investigate the longitudinal change in visual acuity (VA) in the oldest members of the elderly population, to estimate future numbers of people with visual impairments, and to estimate needs for and the effects of visual rehabilitation. METHODS: In the Gerontological and Geriatric Population Studies in Gothenburg, Sweden (H 70), subjects underwent repeated eye examinations at the ages of 70, 82, 88, 95 and 97 years. Logistic regression analysis was used to estimate the probability of independent living as a function of distance VA at different ages. RESULTS: Rates of normal VA (>or= 0.8) declined from 86% of the study group at age 70 to 7% of the study group at age 95 (0% at age 97). The incidence of VA <or= 0.1 increased from 1.4% at age 70 to 27% (all women) at age 97. The deterioration was faster at higher ages. No statistically significant difference in best-corrected distance VA between genders was found. A substantial improvement was achieved by correcting refractive errors. There was a statistically significant correlation between distance VA and the probability of independent living at all ages except age 97. At ages 95 and 97, about 50% of the study group were able to read newspaper print with best-corrected glasses. CONCLUSIONS: The number of old people with impaired vision will increase. People aged 80 years and older should have regular eye-screening in order to preserve vision and present conditions of living. Cataract surgery and low vision rehabilitation should be offered when the subject can still benefit from it, preferably during their 80s at the latest.

Activities of Daily Living↗
PubMed2002

Colour perception among the very elderly related to visual and cognitive function.

Colour perception was studied among a representative sample of 95-year olds and compared with previously examined 80-year olds and a group with Alzheimer's disease (AD), mean age of 80 years. The 95-year olds' results were on a significantly lower level than the other two groups but showed a similar pattern as to colour -discrimination, -naming, -preferences and colour/form recognition. Visual function among 95-year olds had only minor influence on their result in contrast to cognitive function which had a more profound impact. Most interestingly though, the subjects with Alzheimer's diagnosis, younger than the 95-year olds but with a conclusive diagnosis of dementia, performed on an overall higher level than the 95-year olds. This advantage for the Alzheimer group remained even when compared with a sub sample of the 95-year olds with possible dementia diagnosis excluded. On the other hand, only including 95-year olds with a Mini Mental Examination score of >26 in comparison with the Alzheimer group made the differences between the two groups disappear. It is suggested that colour perception as measured in this study is well preserved throughout life. The overall lower colour perception ability in 95-year olds compared with both 80-year olds and subjects with AD may be an expression of the complexity of very high age rather than any isolated concomitant factor.

Aged↗