Celeribacter indicus P73^T, isolated from deep-sea sediment from the Indian Ocean, is capable of degrading a wide range of polycyclic aromatic hydrocarbons (PAHs) and is the first fluoranthene-degrading bacterium within the family Rhodobacteraceae. Here, the complete genome sequence of strain P73^T is presented and analyzed. Besides a 4.5-Mb circular chromosome, strain P73^T carries five plasmids, and encodes 4827 predicted protein-coding sequences. One hundred and thirty-eight genes, including 14 dioxygenase genes, were predicted to be involved in the degradation of aromatic compounds, and most of these genes are clustered in four regions. P73_0346 is the first fluoranthene 7,8-dioxygenase to be discovered and the first fluoranthene dioxygenase within the toluene/biphenyl family. The degradative genes in regions B and D in P73^T are absent in Celeribacter baekdonensis B30, which cannot degrade PAHs. Four intermediate metabolites [acenaphthylene-1(2H)-one, acenaphthenequinone, 1,2-dihydroxyacenaphthylene, and 1,8-naphthalic anhydride] of fluoranthene degradation by strain P73^T were detected as the main intermediates, indicating that the degradation of fluoranthene in P73^T was initiated by dioxygenation at the C-7,8 positions. Based on the genomic and metabolitic results, we propose a C-7,8 dioxygenation pathway in which fluoranthene is mineralized to TCA cycle intermediates.

A novel sulfate-reducing bacterium, strain J2T, was isolated from a serpentinized peridotite sample from the Indian Ocean. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J2T clustered with the genus Desulfovibrio within the family Desulfovibrionaceae, but it showed low similarity (87.95%) to the type species Desulfovibrio desulfuricans DSM 642T. It was most closely related to D. portus MSL79T (96.96%), followed by D. aespoeensis Aspo-2T (96.11 %), D. piezophilus C1TLV30T (96.04 %) and D. profundus DSM11384T (95.17%). Other available sequences shared less than 93.33% 16S rRNA gene sequence similarity. Growth was observed at salinities ranging from 0.2 to 6% (optimum 2.5%), from pH 5 to 8 (optimum 6.5-7), and at temperatures between 9 and 40 °C (optimum 30-35 °C). Strain J2T used lactate, malate, pyruvate, formate and hydrogen as energy sources. Sulfate, thiosulfate, sulfite, fumarate, and nitrate were used as terminal electron acceptors. The main fatty acids were iso-C15:0, anteiso-C15:0, summed feature 9 (iso-C17:1ω9c and/or C16:0 10-methyl) and iso-C17:0. The DNA G+C content of strain J2T was 63.5 mol%. The combined genotypic and phenotypic data show that strain J2T represents a novel species of a novel genus in the family Desulfovibrionaceae, for which the name Pseudodesulfovibrio indicus gen. nov., sp. nov. is proposed, with the type strain J2T (=MCCC 1A01867T = DSM 101483T). We also propose the reclassification of D. piezophilus as Pseudodesulfovibrio piezophilus comb. nov., D. profundus as P. profundus comb. nov., D. portus as P. portus comb. nov. and D. aespoeensis as P. aespoeensis comb. nov.

A taxonomic study was carried out on strain P73^T, which was isolated from deep-sea sediment of the Indian Ocean by enrichment of polycyclic aromatic hydrocarbons. The strain was able to degrade biphenyl, naphthalene, 2-methylnaphthalene, 2,6-dimethylnaphthalene, acenaphthene, anthracene, phenanthrene, dibenzothiophene, dibenzofuran, fluorene, 4-methyldibenzothiophene and fluoranthene, but not pyrene or chrysene. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain P73^T formed a clade with the genera Celeribacter and Huaishuia within the family Rhodobacteraceae , with highest sequence similarity of 96.98 % to Celeribacter neptunius H 14^T, followed by Huaishuia halophila ZXM137^T (96.42 %). The bacterium was Gram-stain-negative, oxidase- and catalase-positive, rod-shaped and non-motile. Growth was observed at salinities from 0.5 to 12 % and at temperatures from 10 to 41 °C. The principal fatty acids (>10 %) of strain P73^T were summed feature 8 (C_18 : 1ω7c/ω6c) and C_19 : 0ω8c cyclo. The sole respiratory quinone was Q-10. The major lipids were phosphatidylglycerol, one unknown aminolipid, one unknown phospholipid and one unknown lipid; a second unknown phospholipid and one unknown glycolipid were present as minor components. The G+C content of the chromosomal DNA was 66.0 mol%. The combined genotypic and phenotypic data show that strain P73^T represents a novel species of the genus Celeribacter , for which the name Celeribacter indicus sp. nov. is proposed. The type strain is P73^T ( = MCCC 1A01112^T = LMG 27600^T = DSM 27257^T). Phylogenetic study and existing phenotypic information also show that Huaishuia halophila should be transferred to the genus Celeribacter as Celeribacter halophilus comb. nov. (type strain ZXM137^T = MCCC 1A06432^T = CGMCC 1.8891^T = LMG 24854^T).

A taxonomic study was carried out on strain GCS-AN-3^T, which was isolated from a phenol-degrading consortium enriched from coking wastewater activated sludge of Beijing Shougang Company Limited during the screening of phenol-degrading bacteria. Cells of strain GCS-AN-3^T were Gram-stain-negative, short rods, and oxidase-/catalase-positive. Growth was observed at salinities from 0 to 2.5 % and at temperatures from 10 to 37 °C. 16S rRNA gene sequence analysis showed that strain GCS-AN-3^T was most closely related to Ottowia pentelensis DSM 21699^T (96.2 %). The principal fatty acids were summed feature 3 (C_16 : 1ω7c/C_16 : 1ω6c), C_16 : 0, summed feature 8 (C_18 : 1ω7c/C_18 : 1ω6c) and cyclo C_17 : 0. The major respiratory quinone was Q-8. The polar lipids comprised phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine and an unknown phospholipid. The G+C content of the genomic DNA was 67.6 mol%. Thiosulfate could be utilized as co-substrate for aerobic growth and was oxidized to sulfate. On the basis of phenotypic, chemotaxonomic and molecular data, strain GCS-AN-3^T is considered to represent a novel species of the genus Ottowia , for which the name Ottowia beijingensis sp. nov. is proposed (type strain GCS-AN-3^T = LMG 27179^T = CGMCC 1.12324^T = MCCC 1A01410^T). An emended description of the genus Ottowia is also proposed.

A novel sulfate-reducing bacterium, strain S606T, was isolated from a sulfide sample collected at a depth of 2764 m from a deep-sea vent chimney wall in the Indian Ocean. Phylogenetic 16S rRNA gene sequence analyses placed strain S606T within the genus Thermodesulfatator, with highest sequence similarity of 98.2% to Thermodesulfatator indicus DSM 15286T, followed by Thermodesulfatator atlanticus AT1325T (97.4%). The average nucleotide identity (ANI) values between strain S606T and the two other type strains (T. indicus DSM 15286T and T. atlanticus AT1325T) were 79.2% and 71.5%, respectively. The digital DNA-DNA hybridization estimate values between strain S606T and these two type strains were 22.7±2.4% and 18.1±2.3%, respectively. Cells were Gram-negative, anaerobic, motile rods (1-1.8 × 0.5-0.7 μm). The novel isolate grew at NaCl concentrations ranging from 1.5 to 4.5% (optimum 2.5-3%), from pH 5.5 to 8 (optimum 6.5-7) and at temperatures between 50 and 80 °C (optimum 65-70 °C). Strain S606T grew chemolithoautotrophically in an H2/CO2 atmosphere (80/20, v/v; 200 kPa), used sulfate as a terminal electron acceptor, but not sulfur, sulfite nor thiosulfate. The predominant fatty acids were C16:0 (24.2%), summed feature 8 (C18:1 ω6c and/or C18:1 ω7c, 26.3%), C18:0 (22.2%) and C18:1 ω9c (9.2%). The DNA G+C content of the chromosomal DNA was 43.1 mol%. The combined genotypic, chemotaxonomic and phenotypic traits show that strain S606T should be described as a novel species of the genus Thermodesulfatator, for which the name Thermodesulfatator autotrophicus sp. nov. is proposed. The type strain is S606T (= DSM 101864T = MCCC 1A01871T).