Overview of the Marine Roseobacter Lineage

Despite the overwhelming bacterial diversity present in the world's oceans, the majority of recognized marine bacteria fall into as few as nine major clades (36), many of which have yet to be cultivated in the laboratory.Molecular-based approaches targeting 16S rRNA genes demonstrate that the Roseobacter clade is one of these major marine groups, typically comprising upwards of 20% of coastal and 15% of mixed-layer ocean bacterioplankton communities (see, e.g., references 36, 37, 42, 98, and 109).Roseobacters are well represented across diverse marine habitats, from coastal to open oceans and from sea ice to sea floor (see, e.g., references 16, 28, 37, 42, 52, and 98).Members have been found to be free living, particle associated, or in commensal relationships with marine phytoplankton, invertebrates, and vertebrates (see, e.g., references 4, 6, 7, 44, 49, 115, and 119).Furthermore, representatives of the clade stand out as representing one of the most readily cultivated of the major marine lineages (36).These isolated representatives are serving as the foundation for an improved understanding of marine bacterial ecology and physiology.