<p>Phylogeny and morphology were examined for the cyanobionts from the water fern <i>Azolla </i>and the cyanobacterial genus<i> Nostoc</i> originating from symbioses with different host plants (genera <i>Gunnera, Cycas,</i> <i>Dioon,</i> <i>Encephalarthos, Macrozamia, </i>and <i>Anthoceros</i>), the lichen genus<i> Pannaria</i>, and free-living <i>Nostoc</i> isolates from different habitats. <i>Nostoc</i> isolates of <i>Pannaria</i> formed a closely related group, but, in general, no monophyletic nature was attributed to the genus <i>Nostoc</i>, in contrast to the cyanobionts from <i>Azolla </i>which were contained in a unique monophyletic group. No correlation was detected between the diversity of the studied cyanobacteria and their geographical origin, while high host specificity was proved for the <i>Azolla</i> cyanobionts and the <i>Nostoc</i> isolates from the bipartite <i>Pannaria</i> lichen. Two patterns of evolution leading to symbiotically competent heterocystous cyanobacteria were distinguished, one comprising symbiotic <i>Nostoc </i>species and the other comprising cyanobacteria in association with the water fern <i>Azolla</i>.</p><p>The production of the non-protein amino acid BMAA, a potential neurotoxin, was also examined. A rapid and sensitive method involving the lysis and extraction of amino acids from cyanobacteria combined with an HPLC assay for fluorescence detection of BMAA was developed. To determine whether the plant or the cyanobacterium was the origin of the BMAA in the cyanobacterium-<i>Azolla </i>symbiosis, the cyanobacterium-free <i>Azolla pinnata</i> var <i>imbricata </i>strain 511 was examined. HPLC analysis demonstrated a significant BMAA production in the absence of the cyanobacterium. However, PCR and cloning revealed the presence of bacteria of the genus <i>Ochrobactrum </i>in the plant.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:su-6861 |
| Date | January 2007 |
| Creators | Papaefthimiou, Dimitra |
| Publisher | Stockholm University, Department of Botany, Stockholm : Botaniska institutionen |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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