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FEMS Microbiol Lett ; 366(2)2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30629176


Diatom diazotroph associations (DDAs) are a widespread marine planktonic symbiosis between several diatom genera and di-nitrogen (N2)-fixing bacteria. Combining single cell confocal microscopy observations and molecular genetic approaches on individual field collected cells, we determined the phylogenetic diversity, distribution and evolution of the DDAs. Confocal analyses coupled with 3-D imaging re-evaluated the cellular location of DDA symbionts. DDA diversity was resolved by paired gene sequencing (18S rRNA and rbcL genes, 16S rRNA and nifH genes). A survey using the newly acquired sequences against public databases found sequences with high similarity (99-100%) to either host (18S rRNA) or symbiont (16S rRNA) in atypical regions for DDAs (high latitudes, anoxic basin and copepod gut). Concatenated phylogenies were congruent for the host and cyanobacteria sequences and implied co-evolution. Time-calibrated trees dated the appearance of N2 fixing planktonic symbiosis from 100-50Mya and were consistent with the symbiont cellular location: symbioses with internal partners are more ancient. An ancestral state reconstruction traced the evolution of traits in DDAs and highlight that the adaptive radiation to the marine environment was likely facilitated by the symbiosis. Our results present the evolutionary nature of DDAs and provide new genetic and phenotypic information for these biogeochemically relevant populations.

Evolução Biológica , Cianobactérias/genética , Diatomáceas/genética , Variação Genética , Simbiose , Cianobactérias/classificação , Cianobactérias/isolamento & purificação , Cianobactérias/fisiologia , Diatomáceas/classificação , Diatomáceas/microbiologia , Diatomáceas/fisiologia , Fixação de Nitrogênio , Filogenia , Água do Mar/microbiologia , Água do Mar/parasitologia
Mol Phylogenet Evol ; 33(1): 91-108, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15324841


Phylogenetic relationships within Fagonia were inferred from analyses of plastid trnL intron and nuclear ribosomal ITS DNA sequences. Sampling of the genus was nearly complete, including 32 of 34 species. Phylogenetic analysis was carried out using parsimony, and Bayesian model averaging. The latter method allows model-based inference while accounting for model-selection uncertainty, and is here used for the first time in phylogenetic analyses. All species of Fagonia in the Old World, except F. cretica, form a weakly supported clade, and all Fagonia species of the New World, except F. scoparia, are well supported as sister to the Old World clade. Fagonia scoparia, from Mexico, and F. cretica, from Northern Africa, are well supported as sisters to all other Fagonia species. Vicariance-dispersal analysis, using DIVA, indicated that the occurrences of Fagonia in South America and southern Africa are due to dispersals, and also, that the ancestor of Fagonia had a distribution compatible with the boreotropics hypothesis.

Teorema de Bayes , Filogenia , Zygophyllaceae/genética , Sequência de Bases , DNA Espaçador Ribossômico/genética , Geografia , Funções Verossimilhança , Modelos Genéticos , Dados de Sequência Molecular , Plastídeos/genética , Análise de Sequência de DNA