Abstract
Earlier phylogenetic analyses of the marine Rhodobacteraceae (class Alphaproteobacteria) genera Leisingera and Phaeobacter indicated that neither genus might be monophyletic. We here used phylogenetic reconstruction from genome-scale data, MALDI-TOF mass-spectrometry analysis and a re-assessment of the phenotypic data from the literature to settle this matter, aiming at a reclassification of the two genera. Neither Phaeobacter nor Leisingera formed a clade in any of the phylogenetic analyses conducted. Rather, smaller monophyletic assemblages emerged, which were phenotypically more homogeneous, too. We thus propose the reclassification of Leisingera nanhaiensis as the type species of a new genus as Sedimentitalea nanhaiensis gen. nov., comb. nov., the reclassification of Phaeobacter arcticus and Phaeobacter leonis as Pseudophaeobacter arcticus gen. nov., comb. nov. and Pseudophaeobacter leonis comb. nov., and the reclassification of Phaeobacter aquaemixtae, Phaeobacter caeruleus, and Phaeobacter daeponensis as Leisingera aquaemixtae comb. nov., Leisingera caerulea comb. nov., and Leisingera daeponensis comb. nov. The genera Phaeobacter and Leisingera are accordingly emended.
Highlights
Bacteria belonging to the Roseobacter group are presumed to form a monophyletic group within the Rhodobacteraceae (Alphaproteobacteria), the great majority of them being of marine origin, which is reflected by their absolute requirement of sodium ions (Brinkhoff et al, 2008)
Analyses of the 16S rRNA gene and in some publications preliminary genomic analyses were in conflict with the current classification (Jin et al, 2011; Beyersmann et al, 2013; Buddruhs et al, 2013a; Dogs et al, 2013a,b; Freese et al, 2013; Gaboyer et al, 2013; Riedel et al, 2013; Breider et al, 2014; Liu et al, 2014; Park et al, 2014). These analyses mostly showed that P. aquaemixtae, P. caeruleus, P. daeponensis, Leisingera methylohalodivorans, and L. aquimarina form a clade, P. arcticus and P. leonis comprise a distinct monophyletic group, and P. gallaeciensis and P. inhibens form a third clade
Only Litorimicrobium, Nautella, Ruegeria, Salinihabitans, Sediminimonas, and Seohaeicola were included to serve as a close outgroup and Roseobacter and Oceanibulbus for rooting the tree, yielding 14 organisms in the phylogenomic and 28 organisms in an additional 16S rRNA analysis
Summary
Bacteria belonging to the Roseobacter group are presumed to form a monophyletic group within the Rhodobacteraceae (Alphaproteobacteria), the great majority of them being of marine origin, which is reflected by their absolute requirement of sodium ions (Brinkhoff et al, 2008). Members of this group constitute up to 25% of the total bacterial community in a large variety of habitats (Brinkhoff et al, 2008). Several reclassifications were already necessary within the Roseobacter group, e. g., for the genera Ruegeria (Uchino et al, 1998; Arahal et al, 2005; Martens et al, 2006) and Roseobacter (Martens et al, 2006)
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