Published in:
Environmental Microbiology, 11 (2009) 10, Seite 2627-2638
Language:
English
DOI:
10.1111/j.1462-2920.2009.01987.x
ISSN:
1462-2920;
1462-2912
Origination:
Footnote:
Description:
<jats:title>Summary</jats:title><jats:p>The <jats:italic>repABC</jats:italic> operon is the prevalent replication unit of alphaproteobacterial plasmids. Their semi‐autonomy is ensured by the essential replicase gene <jats:italic>repC</jats:italic> as well as the <jats:italic>repAB</jats:italic> partitioning cassette. While conserved <jats:italic>repAB</jats:italic> modules are widespread among bacterial plasmids and homologues are even responsible for chromosome partitioning, <jats:italic>repC</jats:italic> genes are exclusively present in <jats:italic>Alphaproteobacteria</jats:italic>. <jats:italic>RepABC</jats:italic> operons contain two strong incompatibility regions, namely a small regulative antisense RNA gene (<jats:italic>incα</jats:italic>) and a palindromic centromere region (<jats:italic>incβ</jats:italic>), which were previously used to classify these replicons. The present survey pursued a complementary strategy essentially following the rationale that all plasmids identified from a single bacterium are <jats:italic>per se</jats:italic> compatible. We established a novel classification scheme for plasmids based on comprehensive phylogenetic analyses of <jats:italic>repC</jats:italic>, <jats:italic>repA</jats:italic> and <jats:italic>repB</jats:italic> genes. Our case study is focused on the <jats:italic>Roseobacter</jats:italic> clade (<jats:italic>Rhodobacterales</jats:italic>), one of the most successful lineages of the marine bacterioplankton. Its global significance was shown in several studies and the interest in these organisms is reflected by more than 40 upcoming genome projects. Based on phylogenetic RepC analyses we identified nine compatibility groups that are expected to stably coexist within the same cell. This prediction is supported by RepA and RepB phylogenies, moreover independent evidence is delivered by the group specificity of highly conserved palindromes (<jats:italic>incβ</jats:italic>).</jats:p>