{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,23]],"date-time":"2026-01-23T16:56:43Z","timestamp":1769187403519,"version":"3.49.0"},"reference-count":57,"publisher":"Microbiology Society","issue":"Pt_6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2014,6,1]]},"abstract":"The symbiosis Azolla<\/jats:italic>\u2013Anabaena azollae<\/jats:italic>, with a worldwide distribution in pantropical and temperate regions, is one of the most studied, because of its potential application as a biofertilizer, especially in rice fields, but also as an animal food and in phytoremediation. The cyanobiont is a filamentous, heterocystic cyanobacterium that inhabits the foliar cavities of the pteridophyte and the indusium on the megasporocarp (female reproductive structure). The classification and phylogeny of the cyanobiont is very controversial: from its morphology, it has been named Nostoc azollae<\/jats:italic>, Anabaena azollae<\/jats:italic>, Anabaena variabilis<\/jats:italic> status azollae<\/jats:italic> and recently Trichormus azollae<\/jats:italic>, but, from its 16S rRNA gene sequence, it has been assigned to \n \n Nostoc<\/jats:italic>\n <\/jats:ext-link>\n <\/jats:named-content> and\/or \n \n Anabaena<\/jats:italic>\n <\/jats:ext-link>\n <\/jats:named-content>, and from its phycocyanin gene sequence, it has been assigned as non-Nostoc<\/jats:italic> and non-Anabaena<\/jats:italic>. The literature also points to a possible co-evolution between the cyanobiont and the Azolla<\/jats:italic> host, since dendrograms and phylogenetic trees of fatty acids, short tandemly repeated repetitive (STRR) analysis and restriction fragment length polymorphism (RFLP) analysis of nif<\/jats:italic> genes and the 16S rRNA gene give a two-cluster association that matches the two-section ranking of the host (Azolla<\/jats:italic>). Another controversy surrounds the possible existence of more than one genus or more than one species strain. The use of freshly isolated or cultured cyanobionts is an additional problem, since their morphology and protein profiles are different. This review gives an overview of how morphological, chemical and genetic analyses influence the classification and phylogeny of the cyanobiont and future research.<\/jats:p>","DOI":"10.1099\/ijs.0.059238-0","type":"journal-article","created":{"date-parts":[[2014,4,16]],"date-time":"2014-04-16T06:06:36Z","timestamp":1397628396000},"page":"1830-1840","source":"Crossref","is-referenced-by-count":38,"title":["Classification and phylogeny of the cyanobiont Anabaena azollae Strasburger: an answered question?"],"prefix":"10.1099","volume":"64","author":[{"given":"Ana L.","family":"Pereira","sequence":"first","affiliation":[{"name":"Interdisciplinary Centre of Marine and Environmental Research (CIIMAR\/CIMAR), University of Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal"}]},{"given":"Vitor","family":"Vasconcelos","sequence":"additional","affiliation":[{"name":"Department of Biology, Faculty of Sciences of the University of Porto, Rua do Campo Alegre, 4069-007 Porto, Portugal"},{"name":"Interdisciplinary Centre of Marine and Environmental Research (CIIMAR\/CIMAR), University of Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal"}]}],"member":"345","reference":[{"key":"r1","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1016\/S0378-1097(03)00784-5","article-title":"The cyanobiont in an Azolla fern is neither Anabaena nor Nostoc","volume":"229","author":"Baker","year":"2003","journal-title":"FEMS Microbiol Lett"},{"key":"r2","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1007\/BF02277375","article-title":"Pigment distribution and nitrogen fixation in Anabaena azollae","volume":"61","author":"Becking","year":"1981","journal-title":"Plant Soil"},{"key":"r3","first-page":"447","article-title":"Cyanobacterial-plant symbioses: signalling and development","volume-title":"The Cyanobacteria. 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