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A Gram-staining-negative bacterial strain (termed CZ-AZ5(T)) was isolated from a biological filter in a marine recirculating aquaculture system in Tianjin, China. Its taxonomic status was determined using a polyphasic approach. CZ-AZ5(T) cells were non-spore-forming, non-motile rods, 0.6-0.7 mm wide and 3.0-3.7 mm long. CZ-AZ5(T) was strictly heterotrophic, aerobic, oxidase-negative and catalase-positive. Growth occurred in the temperature range 20-40 degrees C (optimal: 30 degrees C), pH range 6.0-8.5 (optimal: pH 7.5) and salinity range 0-5 % (w/v) NaCl (optimal: 1 %). In phylogenetic analyses based on 16S rRNA gene sequences, CZ-AZ5(T) was assigned to the family Saprospiraceae (phylum Bacteroidetes) and was clustered with the genera Saprospira and Aureispira within this family. It showed highest sequence similarity to 'Candidatus Haliscomenobacter calcifugiens' (86.2 %), followed by Saprospira grandis ATCC 23119(T) (85.7 %) and Lewinella persica T-3T (85.6 %). DNA G + C content was 40.1 mol%, the major menaquinone was MK-7, and the major cellular fatty acids (>10 %) were C-16 : 1 omega 7c and iso-C-15 : 0. Our phenotypic, chemotaxonomic and phylogenetic observations, taken together, led us to conclude that strain CZ-AZ5(T) represents a novel species and genus of the family Saprospiraceae, for which the name Membranicola marinus gen. nov., sp. nov. is proposed. The type strain is CZ-AZ5(T) (=CGMCC 1.13179(T)=JCM 18886(T)).

A Gram-positive, strictly aerobic and heterotrophic, non-spore-forming actinobacterium (strain B2T) isolated from a recirculating aquaculture system was studied for its taxonomic position. Strain B2T formed a rudimentary substrate-mycelium that fragmented into short rod-shaped to coccoid cells (0.5 µm×0.5–2.2 µm or 0.5–1.0 µm in diameter). Colonies were yellow, smooth, circular and 1.5–2.0 mm in diameter after incubation on TSA for 3 days at 30 °C. Strain B2T grew at 20–40 °C (optimal, 30 °C) and pH 5.5–9.5 (optimal, 6.5–7.0) and in the presence of 0–9 % (w/v) NaCl (optimal, 1 %). The predominant menaquinone of strain B2T was MK-8(H4). The cell-wall peptidoglycan of strain B2T contained the amino acids ornithine, glutamic acid, alanine, glycine and aspartic acid. The major polar lipids were phosphatidylglycerol and diphosphatidylglycerol. The major fatty acids were iso-C15 : 0, iso-C16 : 0 and summed feature 9. Its DNA G+C content was 68.3 mol% (T m). Analysis of 16S rRNA gene sequences indicated that strain B2T was related phylogenetically to members of the genus Ornithinimicrobium with highest similarity (96.6 %) to Ornithinimicrobium kibberense DSM 17687T, followed by Ornithinimicrobium humiphilum DSM 12362T (96.3 %), Ornithinimicrobium pekingense LW6T (96.2 %) and Ornithinimicrobium murale 01-Gi-040T (94.8 %). On basis of phenotypic, chemotaxonomic and phylogenetic data, it was concluded that strain B2T represents a novel species of the genus Ornithinimicrobium , for which the name Ornithinimicrobium tianjinense sp. nov. is proposed. The type strain is B2T ( = CGMCC 1.12160T = JCM 18464T).

A Gram-staining-negative, heterotrophic, facultatively anaerobic bacterium, designated S1T, was isolated from the Cynoglossus semilaevis culture pond in a recirculating mariculture system in Tianjin, China. The taxonomy of strain S1T was studied by using a polyphasic approach. Cells of strain S1T were non-spore-forming, curved rods, 0.4–0.6 µm wide and 1.2–2.0 µm long, and motile by means of a single polar flagellum. The strain was positive for oxidase and catalase activities. Strain S1T was able to grow at 4–30 °C (optimum, 25 °C), at pH 5.5–10.0 (optimum, pH 6.5–7.5) and in the presence of 1–5 % (w/v) NaCl (optimum, 2 %). Strain S1T contained Q-8 as the sole respiratory quinone and C16 : 1ω7c/C16 : 1ω6c and C16 : 0 as the predominant cellular fatty acids. The genomic DNA G+C content was 40.1 mol% (T m). Phylogenetic analysis based on 16S rRNA gene sequences placed strain S1T in the genus Colwellia , and it formed a distinct lineage in the phylogenetic tree together with Colwellia meonggei MA1-3T, Colwellia aestuarii SMK-10T, Colwellia polaris 537T and Colwellia chukchiensis BCw111T, with 97.7, 96.1, 95.9 and 95.0 % 16S rRNA gene sequence similarity to these strains, respectively. DNA–DNA relatedness of strain S1T to Colwellia meonggei MA1-3T was 23.5±3.6 %. On the basis of the phylogenetic and phenotypic evidence, strain S1T is considered to represent a novel species of the genus Colwellia , for which the name Colwellia aquaemaris sp. nov. is proposed. The type strain is S1T ( = CGMCC 1.12165T = JCM 18479T).

A Gram-negative bacterium, strain CZ-AM5T, was isolated from an aerated biological filter in a marine recirculating aquaculture system in Tianjin, China. Its taxonomic position was investigated by using a polyphasic approach. Cells of strain CZ-AM5T were non-spore-forming rods, 0.5–0.8 µm wide and 1.2–2.0 µm long, and motile by means of one or two polar or lateral flagella. Strain CZ-AM5T was strictly aerobic, heterotrophic, oxidase-negative and catalase-positive. Growth occurred at 15–40 °C (optimum, 30–35 °C), at pH 6.5–10.5 (optimum, pH 7.0–7.5) and in the presence of 0–12.0 % (w/v) NaCl (optimum, 4.0 %). The predominant fatty acid was C18 : 1ω7c (80.3 %). Ubiquinone 10 (Q-10) was the sole respiratory quinone. The polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, an unknown aminolipid, an unknown phospholipid and three unknown lipids. The DNA G+C content was 60.4 mol%. Strain CZ-AM5T showed the highest 16S rRNA gene sequence similarity (96.5 %) to Phaeobacter caeruleus LMG 24369T; it exhibited 16S rRNA gene sequence similarity of 95.0–96.5, 95.2–96.3, 96.2, 94.6–95.7 and 94.8–95.8 % to members of the genera Phaeobacter , Ruegeria , Citreimonas , Leisingera and Donghicola , respectively. However, phylogenetic trees based on 16S rRNA gene sequences showed that strain CZ-AM5T did not join any of the above genera, but formed a distinct lineage in the trees. On the basis of phenotypic, chemotaxonomic and phylogenetic analyses, strain CZ-AM5T is considered to represent a novel genus and species of the family Rhodobacteraceae , for which the name Cribrihabitans marinus gen. nov., sp. nov. is proposed. The type strain of Cribrihabitans marinus is CZ-AM5T ( = CGMCC 1.13219T = JCM 19401T).

A Gram-staining-negative bacterium, strain TS-T4T, was isolated from Tuosu Lake, a saline lake (salinity 5.4 %, w/w) in Qaidam basin, Qinghai, China. Its taxonomic position was determined by using a polyphasic approach. Cells of strain TS-T4Twere non-spore-forming rods, 0.4–0.8 µm wide and 1.7–2.3 µm long, and motile by means of a single polar flagellum. Strain TS-T4Twas strictly heterotrophic, aerobic and catalase- and oxidase-positive. Growth was observed in the presence of 0–7.0 % (w/v) NaCl (optimum, 3.0–4.0 %) and at 4–40 °C (optimum, 30–35 °C) and pH 7.0–10.5 (optimum, pH 8.5–9.0). Strain TS-T4Tcontained Q-8 as the sole respiratory quinone and phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids, as for other members of the genusRheinheimera. The predominant fatty acids (>10 %) were summed feature 3 (C16 : 1ω7cand/or C16 : 1ω6c), C16 : 0, C17 : 1ω8cand C18 : 1ω7c. The DNA G+C content was 50.2 mol% (Tm). Phylogenetic trees based on sequences of the 16S rRNA gene and a conserved portion of the gyrase B gene (gyrB) showed that strain TS-T4Twas associated with the genusRheinheimera; the strain showed the highest 16S rRNA gene sequence similarity toRheinheimera longhuensisLH2-2T(97.1 %) and then toRheinheimera pacificaKMM 1406T(97.0 %). DNA–DNA relatedness of strain TS-T4TwithR. longhuensisLH2-2TandR. pacificaNBRC 103167 was 53±2.5 and 48±2 %, respectively. Based on the data presented, it is concluded that TS-T4Trepresents a novel species of the genusRheinheimera, for which the nameRheinheimera tuosuensissp. nov. is proposed. The type strain is TS-T4T( = CGMCC 1.12461T = JCM 19264T).

A Gram-staining-negative, heterotrophic, facultatively anaerobic bacterium, designated AE6T, was isolated from a grouper (Epinephelus malabaricas) culture tank in a recirculating mariculture system located in Tianjin, China. Strain AE6T was able to grow at 15–40 °C (optimum, 30–35 °C), at pH 5.5–10.0 (optimum, pH 7.0–7.5) and in the presence of 0.5–7 % (w/v) NaCl (optimum, 2–3 %). It contained Q-8 as the predominant respiratory quinone, phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) as the major polar lipids and C16 : 1ω7c/C16 : 1ω6c (40.4 %), C18 : 1ω7c (15.5 %) and C16 : 0 (13.5 %) as the predominant cellular fatty acids. The genomic DNA G+C content was 47.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AE6T belonged to the genus Photobacterium (94.2–96.8 % of 16S rRNA gene sequence similarity) and formed a distinct phylogenetic lineage within the genus and exhibited the highest sequence similarity to Photobacterium aphoticum CECT 7614T (96.8 %). Multilocus sequence analysis (MLSA) using four loci (gyrB, rpoA, pyrH and recA) also revealed that strain AE6T was phylogenetically related to the genus Photobacterium . Based on the phylogenetic, chemotaxonomic and phenotypic evidence, strain AE6T is considered to represent a novel species of the genus Photobacterium , for which the name Photobacterium aquae sp. nov. is proposed. The type strain is AE6T ( = CGMCC 1.12159T = JCM 18480T).