Duganella rivus sp. nov., Duganella fentianensis sp. nov., Duganella qianjiadongensis sp. nov. and Massilia guangdongensis sp. nov., isolated from subtropical streams in China and reclassification of all species within genus Pseudoduganella

Four Gram-stain-negative, catalase-positive, rod-shaped and motile strains (FT55WT, FT93WT, CY13WT and DS3T) were isolated from subtropical streams in China. Comparisons based on 16S rRNA gene sequences indicated that strains FT55WT, FT93WT and CY13WT take strain Pseudoduganella danionis E3/2T, and strain DS3T takes strain Pseudoduganella eburnea 10R5-21T as their closest neighbour, respectively. The genome sizes of strains FT55WT, FT93WT, CY13WT and DS3T were 6.15, 5.10, 5.31 and 5.72 Mbp with G+C contents of 61.7, 60.9, 60.6 and 64.0%, respectively. The reconstructed phylogenomic tree based on concatenated 92 core genes showed that strain FT55WT clusters closely with Duganella radicis KCTC 22382T and Duganella sacchari Sac-22T, strains FT93WT and CY13WT form a distinct clade with P. danionis DSM 103461T and this clade clusters with the clades of genus Duganella together, and strain DS3T forms a distinct clade with P. eburnea JCM 31587T and Pseudoduganella violaceinigra DSM 15887T and this clade clusters closely with the clades of genus Massilia, respectively. The calculated pairwise OrthoANIu values and digital DNA–DNA hybridization (DDH) values among strains FT55WT, FT93WT, CY13WT, DS3T and related strains were in the ranges of 75.6–94.2% and 20.6–56.2%, respectively. Q-8 was the sole respiratory quinone of these four strains. The major fatty acids were C16:1ω7c, C16:0 and C12:0. The polar lipids included phosphatidylglycerol, phosphatidylethanolamine and one unidentified phospholipid. Considering the similar fatty acids and polar lipids profiles of species within genus Pseudoduganella, Massilia and Duganella, there is currently no justification for assigning the species of genus Pseudoduganella into the Massilia and Duganella clades in the phylogenomic tree. It is reasonable to transfer P. violaceinigra and P. eburnea to the genus Massilia as Massilia violaceinigrum comb. nov. and Massilia eburnea comb. nov., and transfer P. danionis to the genus Duganella as Duganella danionis comb. nov. Considering phylogenomic analysis, OrthoANIu data, digital DDH data and a range of physiological and biochemical characteristics, strains FT55WT, FT93WT and CY13WT should be assigned to genus Duganella, and strain DS3T should be classified as a novel species within genus Massilia, for which the names Duganella rivus sp. nov. (type strain FT55WT = GDMCC 1.1675T = KACC 21467T), Duganella fentianensis sp. nov. (type strain FT93WT = GDMCC 1.1683T = KACC 21475T), Duganella qianjiadongensis sp. nov. (type strain CY13WT = GDMCC 1.1669T = KACC 21461T) and Massilia guangdongensis sp. nov. (type strain DS3T = GDMCC 1.1636T = KACC 21312T) are proposed.