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Genome Biology

, 9:R90

First Online: 28 May 2008Received: 07 March 2008Revised: 17 May 2008Accepted: 28 May 2008


BackgroundThe picocyanobacterial genus Synechococcus occurs over wide oceanic expanses, having colonized most available niches in the photic zone. Large scale distribution patterns of the different Synechococcus clades based on 16S rRNA gene markers suggest the occurrence of two major lifestyles -opportunists-specialists-, corresponding to two distinct broad habitats -coastal-open ocean-. Yet, the genetic basis of niche partitioning is still poorly understood in this ecologically important group.

ResultsHere, we compare the genomes of 11 marine Synechococcus isolates, representing 10 distinct lineages. Phylogenies inferred from the core genome allowed us to refine the taxonomic relationships between clades by revealing a clear dichotomy within the main subcluster, reminiscent of the two aforementioned lifestyles. Genome size is strongly correlated with the cumulative lengths of hypervariable regions or -islands-. One of these, encompassing most genes encoding the light-harvesting phycobilisome rod complexes, is involved in adaptation to changes in light quality and has clearly been transferred between members of different Synechococcus lineages. Furthermore, we observed that two strains RS9917 and WH5701 that have similar pigmentation and physiology have an unusually high number of genes in common, given their phylogenetic distance.

ConclusionWe propose that while members of a given marine Synechococcus lineage may have the same broad geographical distribution, local niche occupancy is facilitated by lateral gene transfers, a process in which genomic islands play a key role as a repository for transferred genes. Our work also highlights the need for developing picocyanobacterial systematics based on genome-derived parameters combined with ecological and physiological data.

AbbreviationsANIaverage nucleotide identity

GOSGlobal Ocean Sampling

HLhigh light

LGTlateral gene transfer

LLlow light

MLmaximum likelihood

NJneighbor joining

WGSwhole genome shotgun.

Electronic supplementary materialThe online version of this article doi:10.1186-gb-2008-9-5-r90 contains supplementary material, which is available to authorized users.

Alexis Dufresne, Martin Ostrowski contributed equally to this work.

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Autor: Alexis Dufresne - Martin Ostrowski - David J Scanlan - Laurence Garczarek - Sophie Mazard - Brian P Palenik - Ian T Paul

Fuente: https://link.springer.com/

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