Browsing by Author "Dagan, Tal"

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    Role of natural transformation in the evolution of small cryptic plasmids in Synechocystis sp. PCC 6803
    (2023) Nies, Fabián; Wein, Tanita; Hanke, Dustin M.; Springstein, Benjamin L.; Alcorta Loyola, Jaime Andrés; Taubenheim, Claudia; Dagan, Tal
    Small cryptic plasmids have no clear effect on the host fitness and theirfunctional repertoire remains obscure. The naturally competent cyanobacte-riumSynechocystissp. PCC 6803 harbours several small cryptic plasmids;whether their evolution with this species is supported by horizontal transferremains understudied. Here, we show that the small cryptic plasmid DNA istransferred in the population exclusively by natural transformation, wherethe transfer frequency of plasmid-encoded genes is similar to that ofchromosome-encoded genes. Establishing a system to follow gene transfer,we compared the transfer frequency of genes encoded in cryptic plasmidspCA2.4 (2378 bp) and pCB2.4 (2345 bp) within and between populations oftwoSynechocystissp. PCC 6803 labtypes (termed Kiel and Sevilla). Ourresults reveal that plasmid gene transfer frequency depends on the recipientlabtype. Furthermore, gene transfer via whole plasmid uptake in the Sevillalabtype ranged among the lowest detected transfer rates in our experi-ments. Our study indicates that horizontal DNA transfer via natural transfor-mation is frequent in the evolution of small cryptic plasmids that reside innaturally competent organisms. Furthermore, we suggest that the contribu-tion of natural transformation to cryptic plasmid persistence inSynechocys-tisis limited.
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    The order of trait emergence in the evolution of cyanobacterial multicellularity
    (2019) Hammerschmidt, Katrin; Landan, Giddy; Domingues Kümmel Tria, Fernando; Alcorta Loyola, Jaime Andrés; Dagan, Tal
    The transition from unicellular to multicellular organisms is one of the most significant events in the history of life. Key to this process is the emergence of Darwinian individuality at the higher level: groups must become single entities capable of reproduction for selection to shape their evolution. Evolutionary transitions in individuality are characterized by cooperation between the lower level entities and by division of labor. Theory suggests that division of labor may drive the transition to multicellularity by eliminating the trade-off between two incompatible processes that cannot be performed simultaneously in one cell. Here we examine the evolution of the most ancient multicellular transition known today, that of cyanobacteria, where we reconstruct the sequence of ecological and phenotypic trait evolution. Our results show that the prime driver of multicellularity in cyanobacteria was the expansion in metabolic capacity offered by nitrogen fixation, which was accompanied by the emergence of the filamentous morphology and succeeded by a reproductive life cycle. This was followed by the progression of multicellularity into higher complexity in the form of differentiated cells and patterned multicellularity.