Arcicella gelida sp. nov. and Arcicella lustrica sp. nov., isolated from streams in China and re-examining the taxonomic status of all the genera within the families Spirosomataceae and Cytophagaceae

Three Gram-stain-negative, aerobic, rod-shaped, non-motile strains (DC2WT, DC25WT, and LKC2W) were isolated from streams in China. Comparisons based on the 16S rRNA gene sequences showed that these three strains share 16S rRNA gene sequence similarity values over 97.0 % with the species of genus Arcicella. There was confusion due to the fact that all species of genera Flectobacillus, Aquirufa, and Sandaracinomonas show 16S rRNA gene sequence similarity of over 90.0 % to the above three strains, but the genus Flectobacillus belongs to the family Spirosomataceae and the genera Aquirufa and Sandaracinomonas belong to the family Cytophagaceae. Observing the phylogenetic trees, strains DC2WT, DC25WT, and LKC2W cluster closely with the species of genus Arcicella, but some species within the families Spirosomataceae and Cytophagaceae are not monophyletic. The phylogenomic tree also showed a confused phylogenetic relationships among these non-monophyletic species. Combining the phylogenetic relationships and average nucleotide identity values, the current taxonomic status of all the genera within the families Spirosomataceae and Cytophagaceae were re-examined. The genera 'Chryseosolibacter', 'Dawidia', and Chryseotalea should belong to the new family Chryseotaleaceae fam. nov., the genera Arcicella, Flectobacillus, Pseudarcicella, Aquirufa, and Sandaracinomonas should belong to the new family Flectobacillaceae fam. nov., the genera Fluviimonas, Taeseokella, Arcticibacterium, Emticicia, Jiulongibacter, Marinilongibacter, Lacihabitans, and Leadbetterella should belong to the new family Leadbetterellaceae fam. nov., the genus Litoribacter should be reassigned to the family Cyclobacteriaceae, and the genera Arundinibacter and Tellurirhabdus should be reassigned to the family Spirosomataceae. Strains DC2WT and DC25WT are reported to represent two novel species of the genus Arcicella, for which the names Arcicella gelida sp. nov. (type strain DC2WT=GDMCC 1.3209T=KCTC 92559T) and Arcicella lustrica sp. nov. (type strain DC25WT=GDMCC 1.3210T=KCTC 92557T) are proposed.

Sandaracinomonas limnophila gen. nov., sp. nov., a new member of the family Cytophagaceae isolated from a freshwater mesocosm

A bacterial strain designated FSY-15^T was isolated from a freshwater mesocosm in Taiwan and characterised using a polyphasic taxonomic approach. Cells of strain FSY-15^T were Gram-negative, aerobic, non-spore forming, non-motile rods and formed orange coloured colonies. Growth occurred at 20-30 °C (optimum, 25 °C), at pH 6-7.5 (optimum, pH 7) and with 0-0.5 % NaCl (optimum, 0 %). Phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of 92 protein clusters indicated that strain FSY-15^T formed a phylogenetic lineage in the the family Cytophagaceae. Strain FSY-15^T was most closely related to the genera Pseudarcicella and Arcicella, and the levels of 16S rRNA gene sequence identity with respect to members of related genera are less than 94.1 %. Strain FSY-15^T showed less than 68.8 % average nucleotide identity and less than 24.7 % digital DNA-DNA hybridisation identity compared to the type strains of related genera within the family Cytophagaceae. The predominant fatty acids were iso-C_15 : 0, C_16 : 1ω5c and the major hydroxyl fatty acid was iso-C_15 : 0 3-OH. The major isoprenoid quinone was MK-7 and the DNA G+C content was 35.8 mol%. The major polar lipids were phosphatidylethanolamine and several uncharacterised aminophospholipid, aminolipid, phospholipid and lipid. The major polyamine was spermidine. On the basis of the genotypic and phenotypic data, strain FSY-15^T represents a novel species of a new genus in the family Cytophagaceae, for which the name Sandaracinomonas limnophila gen. nov., sp. nov. is proposed. The type strain is FSY-15^T (=BCRC 81011^T =LMG 29732^T =KCTC 52445^T).

Arcicella rigui sp. nov., isolated from water of a wetland, and emended descriptions of the genus Arcicella, Arcicella aquatica, Arcicella rosea and Arcicella aurantiaca

A bacterial strain, designated NSW-5(T), was isolated from a water sample taken from Niao-Song Wetland Park in Taiwan and characterized using a polyphasic taxonomic approach. Cells of strain NSW-5(T) were strictly aerobic, Gram-stain-negative, non-motile and polymorphic, being straight, vibrioid, curved and spiral-shaped rods surrounded by a thick capsule and forming light pink-coloured colonies. Some rings consisting of several cells were present. Growth occurred at 10-40 °C (optimum, 25 °C), with 0-3.0 % NaCl (optimum, 0 %) and at pH 6.0-8.0 (optimum, pH 7.0). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain NSW-5(T) belonged to the genus Arcicella with sequence similarities of 98.6, 98.0 and 97.3 % with Arcicella aquatica NO-502(T), Arcicella rosea TW5(T) and Arcicella aurantiaca TNR-18(T), respectively. The predominant cellular fatty acids were summed feature 3 (C(16 : 1)ω7c and/or C(16 : 1)ω6c; 20.8 %), C(16 : 0) (14.6 %), iso-C(15 : 0) (13.8 %), C(16 : 1)ω5c (12.5 %) and C(18 : 0) (11.4 %), and the only respiratory quinone was MK-7. The polar lipid profile consisted of phosphatidylethanolamine and several uncharacterized glycolipids, aminolipids, phospholipids and aminophospholipids. The DNA G+C content of strain NSW-5(T) was 44.1 mol%. The DNA-DNA relatedness of strain NSW-5(T) with respect to recognized species of the genus Arcicella was less than 70 %. On the basis of phylogenetic inference and phenotypic data, strain NSW-5(T) should be classified as a representative of a novel species, for which the name Arcicella rigui sp. nov. is proposed. The type strain is NSW-5(T) (= KCTC 23307(T) = BCRC 80260(T)). Emended descriptions of the genus Arcicella and of Arcicella aquatica, Arcicella rosea and Arcicella aurantiaca are also proposed.

Pseudarcicella hirudinis gen. nov., sp. nov., isolated from the skin of the medical leech Hirudo medicinalis

A pinkish-pigmented, Gram-stain-negative, rod-shaped, non-spore-forming bacterium, strain E92(T), was isolated from the skin of the medical leech Hirudo medicinalis, on R2A agar. 16S rRNA gene sequence analysis of strain E92(T) showed a relatively low 16S rRNA gene sequence similarity (93.0-93.5 %) to representatives of the genus Arcicella and 91.5-92.0 % to members of the genus Flectobacillus. The polar lipid profile was composed of the major compounds phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified aminolipid and an unidentified polar lipid; glycolipids were not detected. The major quinone was menquinone MK-7, and the major compound in the polyamine pattern was spermidine. The predominant fatty acids were C(16 : 1)ω5c and C(16 : 1)ω7c and/or iso-C(15 : 0) 2-OH (detected as summed feature 3). The isolate did not contain C(14 : 0) or the hydroxyl fatty acid iso-C(17 : 0) 3-OH found in all representatives of the genera Arcicella and Flectobacillus, but did produce C(18 : 1)ω7c and 11-methyl C(18 : 1)ω7c which are not found in these two genera. The DNA G+C content of strain E92(T) was 64.4 mol%. The unique 16S rRNA gene sequence, and specific chemotaxonomic and physiological data revealed that strain E92(T) represents a new genus in the family Cytophagaceae for which we propose the name Pseudarcicella hirudinis gen. nov., sp. nov., with the type strain of the type species as E92(T) (= LMG 26720(T) = CCM 7988(T)).