Michael Victoria, Frank Oliver, Bartling Pascal, Scheuner Carmen, Göker Markus, Brinkmann Henner, Petersen Jörn
Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany.
ISME J. 2016 Oct;10(10):2498-513. doi: 10.1038/ismej.2016.30. Epub 2016 Mar 8.
Alphaproteobacteria of the metabolically versatile Roseobacter group (Rhodobacteraceae) are abundant in marine ecosystems and represent dominant primary colonizers of submerged surfaces. Motility and attachment are the prerequisite for the characteristic 'swim-or-stick' lifestyle of many representatives such as Phaeobacter inhibens DSM 17395. It has recently been shown that plasmid curing of its 65-kb RepA-I-type replicon with >20 genes for exopolysaccharide biosynthesis including a rhamnose operon results in nearly complete loss of motility and biofilm formation. The current study is based on the assumption that homologous biofilm plasmids are widely distributed. We analyzed 33 roseobacters that represent the phylogenetic diversity of this lineage and documented attachment as well as swimming motility for 60% of the strains. All strong biofilm formers were also motile, which is in agreement with the proposed mechanism of surface attachment. We established transposon mutants for the four genes of the rhamnose operon from P. inhibens and proved its crucial role in biofilm formation. In the Roseobacter group, two-thirds of the predicted biofilm plasmids represent the RepA-I type and their physiological role was experimentally validated via plasmid curing for four additional strains. Horizontal transfer of these replicons was documented by a comparison of the RepA-I phylogeny with the species tree. A gene content analysis of 35 RepA-I plasmids revealed a core set of genes, including the rhamnose operon and a specific ABC transporter for polysaccharide export. Taken together, our data show that RepA-I-type biofilm plasmids are essential for the sessile mode of life in the majority of cultivated roseobacters.
代谢功能多样的玫瑰杆菌属（红杆菌科）的α-变形菌在海洋生态系统中数量丰富，是淹没表面主要的初级定殖者。运动性和附着性是许多代表性菌株（如抑制杆菌DSM 17395）典型的“游动或黏附”生活方式的先决条件。最近有研究表明，去除其含有超过20个胞外多糖生物合成基因（包括一个鼠李糖操纵子）的65 kb RepA-I型复制子的质粒后，其运动性和生物膜形成几乎完全丧失。本研究基于同源生物膜质粒广泛分布的假设。我们分析了33株代表该谱系系统发育多样性的玫瑰杆菌，并记录了60%菌株的附着情况和游动能力。所有形成强生物膜的菌株也都具有运动性，这与提出的表面附着机制一致。我们构建了抑制杆菌鼠李糖操纵子四个基因的转座子突变体，并证明了其在生物膜形成中的关键作用。在玫瑰杆菌属中，三分之二预测的生物膜质粒属于RepA-I型，通过对另外四个菌株进行质粒去除实验验证了它们的生理作用。通过比较RepA-I系统发育与物种树，记录了这些复制子的水平转移。对35个RepA-I质粒的基因含量分析揭示了一组核心基因，包括鼠李糖操纵子和一个用于多糖输出的特定ABC转运蛋白。综上所述，我们的数据表明，RepA-I型生物膜质粒对于大多数培养的玫瑰杆菌的固着生活方式至关重要。
