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- Dominguez-Escobar, Julia, et al.
(författare)
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Phylogenetic and molecular clock inferences of cyanobacterial strains within Rivulariaceae from distant environments
- 2011
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 316:2, s. 90-99
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Tidskriftsartikel (refereegranskat)abstract
- Heterocyst-forming cyanobacteria are important players at both evolutionary and ecological scales, but to date it has been difficult to establish their phylogenetic affiliations. We present data from a phylogenetic and molecular clock analysis of heterocystous cyanobacteria within the family Rivulariaceae, including the genera Calothrix, Rivularia, Gloeotrichia and Tolypothrix. The strains were isolated from distant geographic regions including fresh and brackish water bodies, microbial mats from beach rock, microbialites, pebble beaches, plus PCC strains 7103 and 7504. Phylogenetic inferences (distance, likelihood and Bayesian) suggested the monophyly of genera Calothrix and Rivularia. Molecular clock estimates indicate that Calothrix and Rivularia originated similar to 1500 million years ago (MYA) ago and species date back to 400-300 MYA while Tolypothrix and Gloeotrichia are younger genera (600-400 MYA).
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| 2. |
- Falcon, Luisa I, et al.
(författare)
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Ultrastructure of unicellular N-2 fixing cyanobacteria from the tropical North Atlantic and subtropical North Pacific Oceans
- 2004
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Ingår i: Journal of Phycology. ; 40:6, s. 1074-1078
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Nitrogen fixing unicellular marine cyanobacteria may have a major role in the global biogeochemistry of N; nevertheless, little is known about their phylogeny and morphology. We isolated N-2 fixing unicellular cyanobacteria from the tropical North Atlantic and subtropical North Pacific Oceans and examined ultrastructural dynamics during dark:light cycles when grown in incubators. The isolate from the subtropical North Pacific was larger and showed a size variation from 3 to 7 mum but had similar morphology and cell division-plane characteristics as the isolate from the North Atlantic (2.5 mum). Nitrogen fixation only occurred during the dark phase, and ultrastructural analysis demonstrated changes in the appearance and quantity of large carbohydrate-like granules present in the cells. To verify the composition of these carbohydrate-like granules, staining with periodic acid, thioacetic acid, and silver was carried out, and a positive reaction was obvious in all cells. The cells from the Atlantic seemed to empty their polysaccharide granules during the night, whereas those from the Pacific showed a decrease in the number of their granules. Our work suggests that phylogenetically related strains of unicellular N-2 fixing cyanobacteria from different oceans showed similar carbohydrate-like granules that could be used to fuel N-2 fixation during darkness.
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