Ideonella margarita sp. nov., Ideonella lacteola sp. nov., Pseudaquabacterium inlustre sp. nov. and Pseudaquabacterium rugosum sp. nov., isolated from streams in China and re-examining the taxonomic status of all the genera within the family Sphaerotilaceae .

Four Gram-stain-negative, aerobic, rod-shaped and motile strains (LYT19W T , DXS22W T , DXS29W T and BYS139W T ) were isolated from streams in China. All four strains showed highest 16S rRNA gene sequence similarities to the species of genus Ideonella . The calculated average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity values among strains LYT19W T , DXS22W T , DXS29W T , BYS139W T and other closely related strains were less than 79.5, 22.5 and 74.0%, respectively, indicating that each of the four strains should represent an independent novel species. The further reconstructed phylogenomic tree showed that strains LYT19W T and DXS29W T clustered closely with Ideonella strains, but strains DXS22W T and BYS139W T formed an independent clade with Aquabacterium terrae and Aquabacterium pictum . Comparing with other Aquabacterium species, A. terrae and A. pictum harboured distinct physiological and genetic characteristics, so it was reasonable to propose a novel genus Pseudaquabacterium to accommodate A. terrae , A. pictum , DXS22W T and BYS139W T . The major fatty acids of the four strains contained C 16 : 0 , summed feature 3 (C 16 : 1  ω 6 c and/or C 16 : 1  ω 7 c ) and summed feature 8 (C 18 : 1  ω 6 c and/or C 18 : 1  ω 7 c ). The predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and one unidentified aminophospholipid. Combining above descriptions, strains LYT19W T and DXS29W T should represent two novel species of the genus Ideonella , for which the names Ideonella margarita sp. nov. (type strain LYT19W T =GDMCC 1.3205 T =KCTC 92545 T ) and Ideonella lacteola sp. nov. (type strain DXS29W T =GDMCC 1.3207 T =KCTC 92547 T ) are proposed, respectively. Strains DXS22W T and BYS139W T should represent two novel species of the new genus Pseudaquabacterium , for which the names Pseudaquabacterium inlustre sp. nov. (type strain DXS22W T =GDMCC 1.3206 T =KCTC 92546 T ) and Pseudaquabacterium rugosum sp. nov. (type strain BYS139W T =GDMCC 1.3208 T =KCTC 92548 T ) are proposed, respectively.