Paracoccus benzoatiresistens sp. nov., a benzoate resistance and selenite reduction bacterium isolated from wetland

A Gram-stain-negative, aerobic, non-motile, catalase- and oxidase-positive, pale orange, rod-shaped strain EF6T, was isolated from a natural wetland reserve in Hebei province, China. The strain grew at 25-37 °C (optimum, 30 °C), pH 5-9 (optimum, pH 7), and in the presence of 1.0-4.0% (w/v) NaCl (optimum, 2%). A phylogenetic analysis based on 16S rRNA gene sequence revealed that strain EF6T belongs to the genus Paracoccus, and the closest members were Paracoccus shandongensis wg2T with 98.1% similarity, Paracoccus fontiphilus MVW-1 T (97.9%), Paracoccus everestensis S8-55 T (97.7%), Paracoccus subflavus GY0581T (97.6%), Paracoccus sediminis CMB17T (97.3%), Paracoccus caeni MJ17T (97.0%), and Paracoccus angustae E6T (97.0%). The genome size of strain EF6T was 4.88 Mb, and the DNA G + C content was 65.3%. The digital DNA-DNA hybridization, average nucleotide identity, and average amino acid identity values between strain EF6T and the reference strains were all below the threshold limit for species delineation (< 32.8%, < 88.0%, and < 86.7%, respectively). The major fatty acids (≥ 5.0%) were summed feature 8 (86.3%, C18:1 ω6c and/or C18:1 ω7c) and C18:1 (5.0%) and the only isoprenoid quinone was Q-10. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids, five unidentified phospholipids, and an unidentified aminolipid. Strain EF6T displays notable resistance to benzoate and selenite, with higher tolerance levels (25 g/L for benzoate and 150 mM for selenite) compared to the closely related species. Genomic analysis identified six benzoate resistance genes (acdA, pcaF, fadA, pcaC, purB, and catA) and twenty selenite resistance and reduction-related genes (iscR, ssuB, ssuD, selA, selD and so on). Additionally, EF6T possesses unique genes (catA, ssuB, and ssuC) absent in the closely related species for benzoate and selenite resistance. Its robust resistance to benzoate and selenite, coupled with its genomic makeup, make EF6T a promising candidate for the remediation of both organic and inorganic pollutants. It is worth noting that the specific resistance phenotypes described above were not reported in other novel species in Paracoccus. Based on the results of biochemical, physiological, phylogenetic, and chemotaxonomic analyses, combined with comparisons of the 16S rRNA gene sequence and the whole genome sequence, strain EF6T is considered to represent a novel species of the genus Paracoccus within the family Rhodobacteraceae, for which the name Paracoccus benzoatiresistens sp. nov. is proposed. The type strain is EF6T (= GDMCC 1.3400 T = JCM 35642 T = MCCC 1K08702T).

Paracoccus onchidii sp. nov., a moderately halophilic bacterium isolated from a marine invertebrate from the South China Sea

A novel moderately halophilic bacterial strain, designated Z330^T, was isolated from the egg of a marine invertebrate of the genus Onchidium collected in the South China Sea. The 16S rRNA gene sequence of strain Z330^T exhibited the highest similarity value to that of the type strain Paracoccus fistulariae KCTC 22803^T (97.6%), Paracoccus seriniphilus NBRC 100798^T (97.6%) and Paracoccus aestuarii DSM 19484^T (97.6%). Phylogenomic and 16S rRNA phylogenetic analysis showed that strain Z330^T was most closely related to P. seriniphilus NBRC 100798^T and P. fistulariae KCTC 22803^T. Strain Z330^T grew optimally at 28-30 °C, pH 7.0-8.0 with the presence of 5.0-7.0% (w/v) NaCl. In addition, growth of strain Z330^T occurred at 0.5-16% NaCl, indicated strain Z330^T was a moderately halophilic and halotolerant bacterium of genus Paracoccus. The predominant respiratory quinone in strain Z330^T was identified as ubiquinone-10. The major polar lipids of strain Z330^T were phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, glycolipid and six unidentified polar lipids. The major fatty acids of strain Z330^T was summed feature 8 (C_18:1 ω6c and/or C_18:1 ω7c). The draft genome sequence of strain Z330^T includes 4,084,570 bp in total (N50 = 174,985 bp) with a medium read coverage of 463.6 × and 83 scaffolds. The DNA G + C content of strain Z330^T was 60.5%. In silico DNA-DNA hybridization with the four type strains showed 20.5, 22.3, 20.1 and 20.1% relatedness to Paracoccus fistulariae KCTC 22803^T, Paracoccus seriniphilus NBRC 100798^T, Paracoccus aestuarii DSM 19484^T and Paracoccus denitrificans 1A10901^T, respectively. And the average nucleotide identity (ANIb) values between strain Z330^T and these four type strains were 76.2, 80.0, 75.8 and 73.8%, respectively, lower than the 95-96% threshold value for dividing prokaryotic species. On the basis of the phenotypic, phylogenetic, phylogenomic and chemotaxonomic properties, a novel species of the genus Paracoccus, Paracoccus onchidii sp. nov. is proposed with the type strain Z330^T (= KCTC 92727^T = MCCC 1K08325^T).

Degradation potential of alkanes by diverse oil-degrading bacteria from deep-sea sediments of Haima cold seep areas, South China Sea

Marine oil spills are a significant concern worldwide, destroying the ecological environment and threatening the survival of marine life. Various oil-degrading bacteria have been widely reported in marine environments in response to marine oil pollution. However, little information is known about culturable oil-degrading bacteria in cold seep of the deep-sea environments, which are rich in hydrocarbons. This study enriched five oil-degrading consortia from sediments collected from the Haima cold seep areas of the South China Sea. Parvibaculum, Erythrobacter, Acinetobacter, Alcanivorax, Pseudomonas, Marinobacter, Halomonas, and Idiomarina were the dominant genera. Further results of bacterial growth and degradation ability tests indicated seven efficient alkane-degrading bacteria belonging to Acinetobacter, Alcanivorax, Kangiella, Limimaricola, Marinobacter, Flavobacterium, and Paracoccus, whose degradation rates were higher in crude oil (70.3–78.0%) than that in diesel oil (62.7–66.3%). From the view of carbon chain length, alkane degradation rates were medium chains > long chains > short chains. In addition, Kangiella aquimarina F7, Acinetobacter venetianus F1, Limimaricola variabilis F8, Marinobacter nauticus J5, Flavobacterium sediminis N3, and Paracoccus sediminilitoris N6 were first identified as oil-degrading bacteria from deep-sea environments. This study will provide insight into the bacterial community structures and oil-degrading bacterial diversity in the Haima cold seep areas, South China Sea, and offer bacterial resources to oil bioremediation applications.

Insights into carbon-fixation pathways through metagonomics in the sediments of deep-sea cold seeps

Carbon fixation by chemoautotrophic microorganisms in the dark ocean has a major impact on global carbon cycling and ecological relationships in the ocean's interior. At present, six pathways of autotrophic carbon fixation have been found: the Calvin cycle, the reductive Acetyl-CoA or Wood-Ljungdahl pathway (rAcCoA), the reductive tricarboxylic acid cycle (rTCA), the 3-hydroxypropionate bicycle (3HP), the 3-hydroxypropionate/4-hydroxybutyrate cycle (3HP/4HB), and the dicarboxylate/4-hydroxybutyrate cycle (DC/4HB). Although our knowledge about carbon fixation pathways in the ocean has increased significantly, carbon fixation pathways in the cold seeps are still unknown. In this study, we collected sediment samples from two cold seeps and one trough in the south China sea (SCS), and investigated with metagenomic and metagenome assembled genomes (MAGs). We found that six autotrophic carbon fixation pathways present in the cold seeps and trough with rTCA cycle was the most common pathway, whose genes were particularly high in the cold seeps and increased with sediment depths; the rAcCoA cycle mainly occurred in the cold seep regions, and the abundance of module genes increased with sediment depths. We also elucidated members of chemoautotrophic microorganisms involved in these six carbon-fixation pathways. The rAcCoA, rTCA and DC/4-HB cycles required significantly less energy probably play an important role in the deep-sea environments, especially in the cold seeps. This study provided metabolic insights into the carbon fixation pathways in the cold seeps, and laid the foundation for future detailed study on processes and rates of carbon fixation in the deep-sea ecosystems.

Paracoccus amoyensis sp. nov., isolated from the surface seawater along the coast of Xiamen Island, China

Strain 11-3^T was isolated from the surface seawater along the coast of Xiamen Island, China. Cells were Gram-stain-negative, oxidase- and catalase-positive, short and rod-shaped, nonmotile, 0.5-1.0 μm in width and 1.0-2.0 μm in length. Growth of strain 11-3^T was at temperature of 15-37°C (optimum 28-35°C), at pH of 5.0-11.0 (optimum 7.0-9.0) and at salinity range of 0-10 (optimum 0.5-1). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain 11-3^T belonged to the genus Paracoccus and had the highest similarity with Paracoccus caeni MJ17^T (98.1 %), followed by Paracoccus xiamenensis 12-3^T (97.1 %), Paracoccus zeaxanthinifaciens ATCC 21588^T (97.1 %), Paracoccus aestuarii DSM 19484^T (97.0 %), Paracoccus liaowanqingii 2251^T (97.0 %), Paracoccus fistulariae KCTC 22803^T (97.0 %) and other species of the genus Paracoccus (95.2-96.8 %). The DNA-DNA hybridization values between strain 11-3^T and the selected strains (P. caeni MJ17^T, P. xiamenensis 12-3^T, P. zeaxanthinifaciens ATCC 21588^T, P. aestuarii DSM 19484^T and P. liaowanqingii 2251^T) were 19.4, 19.5, 21.6, 19.3 and 19.8 %, respectively. Corresponding, their ANI values were 77.53, 75.61, 75.36, 75.73 and 75.33 %, respectively. The major fatty acid was summed feature 8 (C_18:1 ω6c/ω7c). The major respiratory quinone was Q10. The polar lipids included phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), unidentified glycolipid (GL) and unidentified aminolipid (AL). The DNA G+C content of strain 11-3^T was 60.1 %. Based on results of the phylogenetic analysis, phenotypic and chemotaxonomic characteristics, strain 11-3^T represents a novel species of the genus Paracoccus, for which the name Paracoccus amoyensis sp. nov. is proposed. The type strain is 11-3^T (=MCCC 1A16380^T=KCTC 72689^T).

Paracoccus xiamenensis sp. nov., isolated from seawater on the Xiamen

Strain 12-3T was isolated from seawater of the Guanyinshan Coast, Xiamen, Fujian Province, PR China. The bacterium was Gram-stain-negative, rod-shaped, aerobic, oxidase-positive and catalase-negative. Growth of strain 12-3T occurred at 10–37 °C (optimum, 20–30 °C), at pH 5.0–11.0 (optimum, pH 7.0–8.0) and at a salinity range of 0–10 % (optimum, 3–5 %). The results of phylogenetic analysis based on its 16S rRNA gene sequence indicated that strain 12-3T belonged to the genus Paracoccus and had the highest sequence similarity to Paracoccus lutimaris HDM-25T (97.4 %), followed by Paracoccus isoporae SW-3T (96.9 %), Paracoccus caeni MJ17T (96.9 %), Paracoccus pacificus F14T (96.8 %) and other species in the genus Paracoccus (95.3–96.5 %). The average nucleotide identity (ANI) and DNA–DNA hybridization (DDH) values between strain 12-3T and P. lutimaris HDM-25T were 76.1 and 17.0 %, respectively. ANI and DDH values between strain 12-3T and P. isoporae SW-3T were 78.9 and 18.2 %, respectively. The principal fatty acid of strain 12-3T was summed feature 8 (C18 : 1  ω6c/ω7c) and C18 : 0. The respiratory quinone of strain 12-3T was Q10. The polar lipids included phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unidentified glycolipid. The G+C content of the chromosomal DNA was 63.9 mol%. The combination of the results of the phylogenetic, phenotypic and chemotaxonomic analyses, and its low ANI and DDH values indicate that strain 12-3T represents a novel species of the genus Paracoccus , for which the name Paracoccus xiamenensis sp. nov. is proposed. The type strain is 12-3T (=MCCC 1A16381T=KCTC 72687T).

Muricauda hadalis sp. nov., a novel piezophile isolated from hadopelagic water of the Mariana Trench and reclassification of Muricauda antarctica as a later heterotypic synonym of Muricauda teanensis

A novel marine Gram-stain-negative, non-motile, aerobic and rod-shaped bacterium, designated as strain MT-229T, was isolated from the deep seawater in the Mariana Trench and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 30 °C (ranging 10–40 °C), pH 6 (ranging 3–11) and with 11 % (w/v) NaCl (ranging 0–17 %). Strain MT-229T was a piezophile, growing optimally at 20 MPa (range 0.1–70 MPa). The nearest phylogenetic neighbours were Muricauda antarctica CGMCC 1.2174T and Muricauda taeanensis JCM 17757T with 16S rRNA gene similarity of 98.7 %. The sole respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine (PE), two unidentified aminolipids (AL) and ten unidentified lipids. The major fatty acids of strain MT-229T were iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G. The G+C content of the genomic DNA was 45.6 mol%. The combined genotypic and phenotypic data indicated that strain MT-229T represents a novel species of the genus Muricauda , for which the name Muricauda hadalis sp. nov. is proposed, with the type strain MT-229T (=DSM 109894T=MCCC 1K04201T). In addition, the whole-genome-based comparisons revealed that the type strains of Muricauda antarctica and Muricauda teanensis belong to a single species. It is, therefore, proposed that M. antarctica be recognized as a heterotypic synonym of M. teanensis.

Confluentibacter sediminis sp. nov., isolated from the junction between the ocean and a freshwater lake and emended description of the genus Confluentibacter

A novel marine Gram-stain-negative, non-motile, aerobic and rod-shaped bacterium, designated strain DSL-48^T, was isolated from tidal flat sediment sampled from the East China Sea and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 35 °C (range, 4-37 °C), pH 6 (pH 5-10) and with 4 % (w/v) NaCl (0-7 %). The nearest phylogenetic neighbour was Confluentibacter citreus KCTC 52638^T with 16S rRNA gene similarity of 97.1 %. The predominant respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine, three unidentified aminolipids and four unidentified lipids. The major fatty acids of strain DSL-48^T were iso-C_15 : 0, iso-C_17 : 0 3-OH, anteiso-C_15 : 0, iso-C_15 : 0 3-OH and iso-C_16 : 0 3-OH. The G+C content of the genomic DNA was 33.3 mol%. The combined genotypic and phenotypic data indicated that strain DSL-48^T represents a novel species of the genus Confluentibacter, for which the name Confluentibacter sediminis sp. nov. is proposed, with the type strain DSL-48^T (=KCTC 62648^T=MCCC 1K03537^T).