Title : Diversity of Rhodopirellula and related planctomycetes in a North Sea 1 coastal sediment employing carB as molecular marker

21 Rhodopirellula is an abundant marine member of the bacterial phylum 22 Planctomycetes. Cultivation studies revealed the presence of several closely related 23 Rhodopirellula species in European coastal sediments. Because the 16S rRNA gene 24 does not provide the desired taxonomic resolution to differentiate Rhodopirellula 25 species, we performed a comparison of the genomes of nine Rhodopirellula strains 26 and six related planctomycetes and identified carB, coding for the large subunit of 27 carbamoylphosphate synthetase, as a suitable molecular marker. In this study we 28 investigated the diversity of Rhodopirellula in coastal intertidal surface sediments of 29 Sylt island, North Sea, using the 16S rRNA and carB genes as molecular markers. 30 The carB clone and pyrosequencing libraries revealed the presence of 12 species of 31 Rhodopirellula and of 66 species in closely related undescribed genera, a diversity 32 that was not detected with a 16S rRNA gene library. This study demonstrates that the 33 carB gene is a powerful molecular marker for detecting Rhodopirellula species in the 34 environment and may be used for the taxonomic evaluation of new strains. 35 36