Published in:
Environmental Microbiology, 17 (2015) 10, Seite 4019-4034
Language:
English
DOI:
10.1111/1462-2920.12947
ISSN:
1462-2920;
1462-2912
Origination:
Footnote:
Description:
<jats:title>Summary</jats:title><jats:p>The marine bacterium <jats:styled-content style="fixed-case"><jats:italic>M</jats:italic></jats:styled-content><jats:italic>arinovum algicola</jats:italic> <jats:styled-content style="fixed-case">DG</jats:styled-content>898 is a representative of the Roseobacter group (<jats:italic>Rhodobacteraceae</jats:italic>, <jats:styled-content style="fixed-case"><jats:italic>A</jats:italic></jats:styled-content><jats:italic>lphaproteobacteria</jats:italic>) and harbours a wealth of 11 extrachromosomal replicons (<jats:styled-content style="fixed-case">ECRs</jats:styled-content>) unprecedented for <jats:italic>Proteobacteria</jats:italic>. The relevance of <jats:styled-content style="fixed-case">ECRs</jats:styled-content> has previously been exemplified by photosynthesis and biofilm plasmids, but the evolutionary forces for the emergence of multipartite genomes are largely unknown. The newly established genome revealed the exceptional metabolic potential of <jats:italic>Marinovum</jats:italic> and its adaptation to the phycosphere. Comparative codon usage analyses allowed the identification of eight chromids and three plasmids. Functional gene clustering is documented by the 52‐kb biofilm chromid that is required for surface attachment. The most conspicuous finding is the presence of a highly expressed chromid‐encoded flagellum gene cluster (<jats:styled-content style="fixed-case">FGC</jats:styled-content>, <jats:italic>fla2</jats:italic>) that is indispensable for swimming motility. <jats:styled-content style="fixed-case"><jats:italic>M</jats:italic></jats:styled-content><jats:italic>arinovum algicola</jats:italic> DG898 harbours an additional chromosome‐encoded flagellum (<jats:italic>fla1</jats:italic>) with unknown function. Comprehensive phylogenetic analyses revealed the presence of a third <jats:styled-content style="fixed-case">FGC</jats:styled-content> type (<jats:italic>fla3</jats:italic>) in <jats:italic>Rhodobacteraceae</jats:italic> and indicated the transmission of complete <jats:styled-content style="fixed-case">FGCs</jats:styled-content> via conjugation. The current <jats:italic>Marinovum</jats:italic> study indicates a functional correlation of the intracellular <jats:italic>fla2</jats:italic>‐chromid localization and the subcellular positioning of the flagellum. The proposed mechanism might represent – apart from horizontal transfer – a novel driving force for the emergence of multipartite genomes.</jats:p>