SPONGE ASSOCIATED CYANOBACTERIA: LIFE INSIDE A HOST CELL

Cyanobacteria form stable symbiotic interactions with eukaryotic hosts. The symbiotic host range is wide and includes mosses, angiosperm plants, lichens, sponges and others. Given the basal evolutionary phylogenetic position of marine sponges, the sponge-cyanobacteria interaction has been suggested to be one of the oldest host-bacteria interactions, dating back more than 500 million years. Sponge-associated cyanobacteria are polyphyletic, implying that they derived from multiple independent symbiotic events. Among the various lineages, Synechococcus-like species are the most commonly reported and widespread in sponges. These include the widespread and extracellular Candidatus Synechococcus spongiarium and a less common intracellular Candidatus Synechococcus feldmannii. Ca. S. feldmannii has been detected mostly in the sponge Petrosia ficiformis, appears to be a facultative symbiont, is transferred horizontally, habitats inside host cells (intracellular). Whilst the symbiotic lifestyle of Ca. S. spongiarum was recently studied via comparative genomics, nothing is known about the adaptations and symbiotic features of Ca. S. feldmannii. The latter (as the majority of sponge symbiont lineages) remains uncultivated, thus I used culture independent approaches based on next generation sequencing for revealing the first genome of an intracellular sponge symbiont, Ca. S. feldmannii. Genomic adaptations of Ca. S. feldmannii to its endosymbiotic lifestyle will be discussed.