Phylogenomic analyses of a clade within the roseobacter group suggest taxonomic reassignments of species of the genera Aestuariivita, Citreicella, Loktanella, Nautella, Pelagibaca, Ruegeria, Thalassobius, Thiobacimonas and Tropicibacter, and the proposal of six novel genera

Abstract

Roseobacters are a diverse and globally abundant group of Alphaproteobacteria within the Rhodobacteraceae family. Recent studies and the cophenetic correlations suggest that the 16S rRNA genes are poor phylogenetic markers within this group. In contrast, the cophenetic correlation coefficients of the core-gene average amino acid identity (cAAI) and RpoC protein sequences are high and likely more predictive of relationships. A maximum-likelihood phylogenetic tree calculated from 53 core genes demonstrated that some of the current genera were either polyphyletic or paraphyletic. The boundaries of bacterial genera were redefined based upon the cAAI, the percentage of conserved proteins, and phenotypic characteristics and resulted in the following taxonomic proposals. Loktanella vestfoldensis, Loktanella litorea, Loktanella maricola, Loktanella maritima, Loktanella rosea, Loktanella sediminilitoris, Loktanella tamlensis, and Roseobacter sp. CCS2 should be reclassified into the novel genus Yoonia. Loktanella hongkongensis, Loktanella aestuariicola, Loktanella cinnabarina, Loktanella pyoseonensis, Loktanellasoe soekkakensis and Loktanella variabilis should be reclassified in the novel genus Limimaricola. Loktanella koreensis and Loktanella sediminum should be reclassified in the novel genus Cognatiyoonia. Loktanella marina should be reclassified in the novel genus Flavimaricola. Aestuariivita atlantica should be reclassified in the novel genus Pseudaestuariivita. Thalassobius maritima should be reclassified in the novel genus Cognatishimia. Similarly, Ruegeria mobilis, Ruegeria scottomollicae, Ruegeria sp. TM1040 and Tropicibacter multivorans should be reclassified in the genus Epibacterium. Tropicibacter litoreus and Tropicibacter mediterraneus should be reclassified in the genus Ruegeria. Thalassobius abyssi and Thalassobius aestuarii should be reclassified in the genus Shimia. Citreicella aestuarii, Citreicella manganoxidans, Citreicella marina, Citreicella thiooxidans, Pelagibaca bermudensis and Thiobacimonas profunda should be reclassified in the genus Salipiger. Nautella italica should be reclassified in the genus Phaeobacter. Because these proposals to reclassify the type and all others species of Citreicella, Nautella, Pelagibaca and Thiobacimonas, these genera are not used in this taxonomy.