Genome and metabolic network of "Candidatus Phaeomarinobacter ectocarpi" Ec32, a new candidate genus of Alphaproteobacteria frequently associated with brown algae

Simon M Dittami, Tristan Barbeyron, Catherine Boyen, Jeanne Cambefort, Guillaume Collet, Ludovic Delage, Angélique Gobet, Agnès Groisillier, Catherine Leblanc, Gurvan Michel, Delphine Scornet, Anne Siegel, Javier E Tapia, Thierry Tonon

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Rhizobiales and related orders of Alphaproteobacteria comprise several genera of nodule-inducing symbiotic bacteria associated with plant roots. Here we describe the genome and the metabolic network of "Candidatus Phaeomarinobacter ectocarpi" Ec32, a member of a new candidate genus closely related to Rhizobiales and found in association with cultures of the filamentous brown algal model Ectocarpus. The "Ca. P. ectocarpi" genome encodes numerous metabolic pathways that may be relevant for this bacterium to interact with algae. Notably, it possesses a large set of glycoside hydrolases and transporters, which may serve to process and assimilate algal metabolites. It also harbors several proteins likely to be involved in the synthesis of algal hormones such as auxins and cytokinins, as well as the vitamins pyridoxine, biotin, and thiamine. As of today, "Ca. P. ectocarpi" has not been successfully cultured, and identical 16S rDNA sequences have been found exclusively associated with Ectocarpus. However, related sequences (≥97% identity) have also been detected free-living and in a Fucus vesiculosus microbiome barcoding project, indicating that the candidate genus "Phaeomarinobacter" may comprise several species, which may colonize different niches.

Original languageEnglish
Pages (from-to)241
JournalFrontiers in genetics
Publication statusPublished - 25 Jul 2014

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