Species' functional traits and interactions drive nitrate-mediated sulfur-oxidizing community structure and functioning.

IMPORTANCE: Understanding the processes and mechanisms governing microbial community assembly and their linkages to ecosystem functioning has long been a core issue in microbial ecology. An in-depth insight still requires combining with analyses of species' functional traits and microbial interactions. Our study showed how species' functional traits and interactions determined microbial community structure and functions by a well-controlled laboratory experiment with nitrate-mediated sulfur oxidation systems using high-throughput sequencing and culture-dependent technologies. The results provided solid evidences that species' functional traits and interactions were the intrinsic factors determining community structure and function. More importantly, our study established quantitative links between community structure and function based on species' functional traits and interactions, which would have important implications for the design and synthesis of microbiomes with expected functions.

Tabrizicola rongguiensis sp. nov., isolated from the sediment of a river in Ronggui, Foshan city, China.

A novel Gram-negative, aerobic, non-spore-forming, non-motile and rod-shaped bacterium, designated J26T, was isolated from the sediment of a river in Ronggui, Foshan city, China. Strain J26T grew optimally at 0 % (w/v) NaCl, pH 6.5-7.5, and 30 °C, and it formed milky white irregular colonies on Reasoner's 2A agar medium. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J26T had the highest similarity to Tabrizicola aquatica RCRI19T (97.1 %) and formed a distinct clade in the genus Tabrizicola. Cellular components of J26T supported this strain as a member of the genus Tabrizicola. The predominant fatty acids were C18 : 1 ω7c, C18 : 1 ω7c-11 methyl and C16 : 0. Polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphorylethanolamine. Ubiquinone Q-10 was the major respiratory quinone, and the DNA G+C content was 64.2 mol%. However, low 16S rRNA gene sequence similarity and average nucleotide identity (73.56 % for ANIb between strain J26T with RCRI19T) demonstrated that strain J26T should be assigned to a novel species. Moreover, the differences between J26T and RCRI19T in terms of physiological and biochemical properties, such as carbon, nitrogen and sulphur metabolism, further supported that J26T represents a novel species, for which the name Tabrizicola rongguiensis sp. nov. is proposed. The type strain is J26T (=GDMCC 1.2843T=KCTC 92112T).

Novosphingobium percolationis sp. nov. and Novosphingobium huizhouense sp. nov., isolated from landfill leachate of a domestic waste treatment plant.

Two strains designated as c1T and c7T, were isolated from the landfill leachate of a domestic waste treatment plant in Huizhou City, Guangdong Province, PR China. The cells of both strains were aerobic, rod-shaped, non-motile and formed yellow colonies on Reasoner's 2A agar plates. Strain c1T grew at 10-42 °C (optimum, 30 °C), pH 4.5-10.5 (optimum, pH 7.0) and 0-2.0 % (w/v) NaCl (optimum, 0-0.5 %). Strain c7T grew at 10-42 °C (optimum, 30 °C), pH 4.5-10.5 (optimum, pH 6.0) and 0-2.0 % (w/v) NaCl (optimum, 0-0.5 %). Phylogenetic analyses revealed that strains c1T and c7T belong to the genus Novosphingobium. The 16S rRNA gene sequence similarities of strains c1T and c7T to the type strains of Novosphingobium species were 94.5-98.2 % and 94.3-99.1 %, respectively. The calculated pairwise average nucleotide identity values among strains c1T, c7T and the reference strains were in the range of 75.2-85.9 % and the calculated pairwise average amino acid identity values among strains c1T, c7T and reference strains were in the range of 72.0-88.3 %. Their major respiratory quinone was Q-10, and the major cellular fatty acids were C18 : 1 ω7c, C18 : 0, C16 : 1 ω7c, C16 : 0 and C14 : 0 2OH. The major polar lipids of strains c1T and c7T were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, sphingoglycolipid, unidentified lipids and unidentified phospholipid. Based on phenotypic, chemotaxonomic, phylogenetic and genomic results from this study, strains c1T and c7T should represent two independent novel species of Novosphingobium, for which the names Novosphingobium percolationis sp. nov. (type strain c1T=GDMCC 1.2555T=KCTC 82826T) and Novosphingobium huizhouense sp. nov. (type strain c7T=GDMCC 1.2556T=KCTC 82827T) are proposed. The gene function annotation results of strains c1T and c7T suggest that they could play an important role in the degradation of organic pollutants.

Undibacterium baiyunense sp. nov., Undibacterium curvum sp. nov., Undibacterium fentianense sp. nov., Undibacterium flavidum sp. nov., Undibacterium griseum sp. nov., Undibacterium hunanense sp. nov., Undibacterium luofuense sp. nov., Undibacterium nitidum sp. nov., Undibacterium rivi sp. nov., Undibacterium rugosum sp. nov. and Undibacterium umbellatum sp. nov., isolated from streams in China.

Twelve Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile strains (CY7WT, CY18WT, CY22WT, FT31WT, FT137WT, FT147WT, BYS50W, BYS107WT, LFS511WT, LX15WT, LX22WT and NL8WT) were isolated from streams in China. Comparisons based on 16S rRNA gene sequences indicated that these strains take species of genus Undibacterium as close neighbours. The reconstructed phylogenetic and phylogenomic trees also showed that these strains cluster with species of genus Undibacterium together. The genome G+C contents of these strains were in the range of 45.3 to 53.3 mol%. The calculated pairwise OrthoANIu values and digital DNA-DNA hybridization values among these strains and related strains were in the range of 70.4 to 94.1% and 19.3 to 55.3% except that the values between strains CY7WT and BYS50W were 99.0 and 91.8 %, respectively. Q-8 was their predominant respiratory quinone. C16 : 1 ω7c and C16 : 0 were their major fatty acids. Their polar lipids profiles were similar, including phosphatidylglycerol, phosphatidylethanolamine, one unidentified phospholipid and two kinds of unidentified aminolipids. Combining polyphasic taxonomic characteristics and phylogenetic relationships, twelve strains should represent eleven independent novel species of genus Undibacterium, for which the names Undibacterium baiyunense sp. nov. (type strain BYS107WT=GDMCC 1.2453T=KCTC 82653T), Undibacterium curvum sp. nov. (type strain CY22WT=GDMCC 1.1906T=KACC 21951T), Undibacterium fentianense sp. nov. (type strain FT137WT=GDMCC 1.2456T=KCTC 82656T), Undibacterium flavidum sp. nov. (type strain LX15WT=GDMCC 1.1910T=JCM 34286T), Undibacterium griseum sp. nov. (type strain FT31WT=GDMCC 1.1908T=KACC 21953T), Undibacterium hunanense sp. nov. (type strain CY18WT=GDMCC 1.1904T=KACC 21949T), Undibacterium luofuense sp. nov. (type strain LFS511WT=GDMCC 1.2458T=KCTC 82658T), Undibacterium nitidum sp. nov. (type strain LX22WT=GDMCC 1.1912T=KACC 21957T), Undibacterium rivi sp. nov. (type strain FT147WT=GDMCC 1.2457T=KCTC 82657T), Undibacterium rugosum sp. nov. (type strain CY7WT=GDMCC 1.1903T=KACC 21961T) and Undibacterium umbellatum sp. nov. (type strain NL8WT=GDMCC 1.1915T=KACC 21960T) are proposed.

Algoriphagus pacificus sp. nov. and Algoriphagus oliviformis sp. nov., isolated from a mariculture fishpond.

Two Gram-stain-negative, catalase-positive, oxidase-negative, rod-shaped, non-flagellated, non-spore-forming and non-motile strains (YJ13CT and H41T) were isolated from a mariculture fishpond in PR China. Comparisons based on 16S rRNA gene sequences indicated that YJ13CT and H41T shared 16S rRNA gene sequences similarities between 92.6 and 99.2 % with species of the genus Algoriphagus. YJ13CT only shared 93.8 % 16S rRNA gene sequence similarity with H41T. The reconstructed phylogenetic and phylogenomic trees indicated that YJ13CT and H41T clustered closely with species of the genus Algoriphagus. The calculated pairwise orthologous average nucleotide identity with usearch (OrthoANIu) values between strains YJ13CT and H41T and other related strains were all less than 79.5 %. The OrthoANIu value between YJ13CT and H41T was only 69.9 %. MK-7 was the predominant respiratory quinone of YJ13CT and H41T and their major cellular fatty acids contained iso-C15 : 0, C16 : 1 ω7c and C17 : 1 ω9c. The polar lipids profiles of YJ13CT and H41T consisted of phosphatidylethanolamine and several kinds of unidentified lipids. Combining the above descriptions, strains YJ13CT and H41T represent two distinct novel species of the genus Algoriphagus, for which the names Algoriphagus pacificus sp. nov. (type strain YJ13CT=GDMCC 1.2178T=KCTC 82450T) and Algoriphagus oliviformis sp. nov. (type strain H41T=GDMCC 1.2179T=KCTC 82451T) are proposed.

Elevated nitrate simplifies microbial community compositions and interactions in sulfide-rich river sediments.

Excessive nitrate in water systems is prevailing and a global risk of human health. Polluted river sediments are dominated by anaerobes and often the hotspot of denitrification. So far, little is known about the ecological effects of nitrate pollution on microbial dynamics, especially those in sulfide-rich sediments. Here we simulated a nitrate surge and monitored the microbial responses, as well as the changes of important environmental parameters in a sulfide-rich river sediment for a month. Our analysis of sediment microbial communities showed that elevated nitrate led to (i) a functional convergence at denitrification and sulfide oxidation, (ii) a taxonomic convergence at Proteobacteria, and (iii) a significant loss of biodiversity, community stability and other functions. Two chemolithotrophic denitrifiers Thiobacillus and Luteimonas were enriched after nitrate amendment, although the original communities were dominated by methanogens and syntrophic bacteria. Also, serial dilutions of sediment microbial communities found that Thiobacillus thiophilus dominated 18/30 communities because of its capability of simultaneous nitrate reduction and sulfide oxidation. Additionally, our network analysis indicated that keystone taxa seemed more likely to be native auxotrophs (e.g., syntrophic bacteria, methanogens) rather than dominant denitrifiers, possibly because of the extensive interspecific cross-feeding they estabilished, while environment perturbations probably disrupted that cross-feeding and simplified microbial interactions. This study advances our understanding of microbial community responses to nitrate pollution and possible mechanism in the sulfide-rich river sediment.

Synergistic interactions of Desulfovibrio and Petrimonas for sulfate-reduction coupling polycyclic aromatic hydrocarbon degradation.

Microbial sulfate-reduction coupling polycyclic aromatic hydrocarbon (PAH) degradation is an important process for the remediation of contaminated sediments. However, little is known about core players and their mechanisms in this process due to the complexity of PAH degradation and the large number of microorganisms involved. Here we analyzed potential core players in a black-odorous sediment using gradient-dilution culturing, isolation and genomic/metagenomic approaches. Along the dilution gradient, microbial PAH degradation and sulfate consumption were not decreased, and even a significant (p = 0.003) increase was observed in the degradation of phenanthrene although the microbial diversity declined. Two species, affiliated with Desulfovibrio and Petrimonas, were commonly present in all of the gradients as keystone taxa and showed as the dominant microorganisms in the single colony (SB8) isolated from the highest dilution culture with 93.49% and 4.73% of the microbial community, respectively. Desulfovibrio sp. SB8 and Petrimonas sp. SB8 could serve together as core players for sulfate-reduction coupling PAH degradation, in which Desulfovibrio sp. SB8 could degrade PAHs to hexahydro-2-naphthoyl through the carboxylation pathway while Petrimonas sp. SB8 might degrade intermediate metabolites of PAHs. This study provides new insights into the microbial sulfate-reduction coupling PAH degradation in black-odorous sediments.

Brevibacterium rongguiense sp. nov., isolated from freshwater sediment.

A Gram stain-positive, non-spore-forming, non-motile and rod-shaped actinomycete, strain 5221T, was isolated from the sediment of a river collected at Ronggui in the Pearl River Delta, PR China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain formed a distinct lineage within the genus Brevibacterium and had the highest sequence similarity to Brevibacterium pityocampae Tp12T (96.7 %), followed by Brevibacterium daeguense 2C6-41T (96.5 %), Brevibacterium samyangense SST-8T (96.0 %) and Brevibacterium ravenspurgense 20T (95.9 %). The results of chemotaxonomic analyses, including detecting anteiso-C15 : 0, anteiso-C17 : 0, and C16 : 0 as the major cellular fatty acids, diphosphatidylglycerol, phosphatidylglycerol and three phosphoglycolipids as the polar lipids, MK-8(H2) as the major menaquinone, and a DNA G+C content of 72.4 mol%, supported that strain 5221T is a member of the genus Brevibacterium. Furthermore, low sequence similarities of 16S rRNA gene sequences, differences in fatty acid compositions and differential physiological characteristics such as enzyme activity and carbon sources utilization ability distinguished the isolate from its close relatives. Therefore, strain 5221T represents a novel species of the genus Brevibacterium, for which the name Brevibacterium rongguiense sp. nov. is proposed, with the type strain 5221T (=GDMCC 1.1766T=KACC 21700T).

Duganella lactea sp. nov., Duganella guangzhouensis sp. nov., Duganella flavida sp. nov. and Massilia rivuli sp. nov., isolated from a subtropical stream in PR China and proposal to reclassify Duganella ginsengisoli as Massilia ginsengisoli comb. nov.

Five Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile strains (FT50WT, FT80WT, FT92WT, FT94W and FT135WT) were isolated from a subtropical stream in PR China. Comparisons based on 16S rRNA gene sequences showed that strains FT50WT, FT94W and FT135WT take strain Duganella sacchari Sac-22T, and strains FT80WT and FT92WT take strain Duganella ginsengisoli DCY83T as their closest neighbour in the phylogenetic trees, respectively. The G+C contents of strains FT50WT, FT80WT, FT92WT, FT94W and FT135WT were 63.3, 62.4, 62.8, 63.8 and 60.8 %, respectively. The reconstructed phylogenomic tree based on concatenated 92 core genes showed that strains FT50WT, FT80WT, FT94W and FT135WT clustered together with species of the genus Duganella, but strains FT92WT and D. ginsengisoli KCTC 42409T were located in the clades of the genus Massilia. The calculated pairwise average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values among strains FT50WT, FT80WT, FT92WT, FT94W, FT135WT and related strains were in the ranges of 75.6-87.8% and 20.3-33.8% except that the values between strains FT50WT and FT94W were 98.7 and 89.2%, respectively. The respiratory quinone of these five strains was Q-8. The major fatty acids were C16 : 1 ω7c, C16 : 0, C18 : 1 ω7c and C12 : 0. The polar lipids included phosphatidylethanolamine, phosphatidylglycerol and one unidentified phospholipid. Considering the distinct phylogenetic relationships of D. ginsengisoli with species of the genus Massilia in the phylogenomic tree, it was reasonable to transfer D. ginsengisoli to the genus Massilia as Massilia ginsengisoli comb. nov. Combining the results of phylogenomic analysis, ANI and dDDH data, and a range of physiological and biochemical characteristics together, strains FT50WT and FT94W should belong to the same species and be assigned to genus Duganella with strains FT80WT and FT135WT together, and strain FT92WT should be assigned to the genus Massilia, for which the names Duganella lactea sp. nov. (type strain FT50WT=GDMCC 1.1674T=KACC 21466T), Duganella guangzhouensis sp. nov. (FT80WT=GDMCC 1.1678T=KACC 21470T), Duganella flavida sp. nov. (FT135WT=GDMCC 1.1745T=KACC 21659T) and Massilia rivuli sp. nov. (FT92WT=GDMCC 1.1682T=KACC 21474T) are proposed.

Massilia aquatica sp. nov., Isolated from a Subtropical Stream in China.

A Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile strain FT127WT was isolated from a subtropical stream in China. Comparison based on 16S rRNA gene sequences showed that strain FT127WT belongs to genus Massilia and shares 98.5% similarity with Massilia buxea A9T as its closest neighbor. The genome size of strain FT127WT was 6.65 Mbp with G + C content of 65.3%. The calculated pairwise OrthoANIu values and digital DNA-DNA hybridization values between strain FT127WT and each of strains M. buxea KCTC 52429T, Massilia armeniaca ZMN-3T, Massilia plicata DSM 17505T and Massilia namucuonensis CGMCC 1.11014T were less than 83.1% and 26.6%, respectively. The reconstructed phylogenomic tree based on concatenated 92 core genes showed that strain FT127WT clusters closely with M. namucuonensis CGMCC 1.11014T. The respiratory quinone of strain FT127WT was Q-8. The major fatty acids were C16:1 ω7c, C16:0 and C12:0. The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol and one unidentified phospholipid. Combining above all characteristics, strain FT127WT should represent a novel species within genus Massilia, for which the name Massilia aquatica sp. nov. (type strain FT127WT = GDMCC 1.1690T = KACC 21482T) is proposed.

Rugamonas aquatica sp. nov. and Rugamonas rivuli sp. nov., isolated from a subtropical stream in PR China.

Two Gram-stain-negative, catalase- and oxidase-positive, rod-shaped, motile strains (FT29WT and FT103WT) were isolated from a subtropical stream in PR China. Comparisons based on 16S rRNA gene sequences showed that strains FT29WT and FT103WT showed 98.7 and 98.6 % 16S rRNA gene sequence similarities to Rugamonas rubra CCM 3730T as their closest neighbour, respectively. The calculated pairwise OrthoANIu values between strain R. rubra CCM 3730T and strains FT29WT and FT103WT were all 81.4 %. The respiratory quinone of strains FT29WT and FT103WT was determined to be Q-8. The major fatty acids were C16 : 1 ω7c, C16 : 0 and C12 : 0. The polar lipids of strain FT103WT included phosphatidylethanolamine, phosphatidylglycerol and one unidentified phospholipid, but strain FT29WT did not contain phosphatidylglycerol. The genome sizes of strains FT29WT and FT103WT were 7.23 and 6.84 Mbp with G+C contents of 63.8 and 63.9 %, respectively. Although the pairwise OrthoANIu value between strains FT29WT and FT103WT was 95.2 % which located in the transition region of species demarcation, the dissimilarities in the aspects of phenotypic, biochemical and genotypic characteristics supported these two strains should belong to the different species within genus Rugamonas, for which the names Rugamonas aquatica sp. nov. (type strain FT29WT=GDMCC 1.1643T=KACC 21316T) and Rugamonas rivuli sp. nov. (type strain FT103WT=GDMCC 1.1685T=KACC 21477T) are proposed.

Duganella alba sp. nov., Duganella aquatilis sp. nov., Duganella margarita sp. nov. and Duganella levis sp. nov., isolated from subtropical streams in China.

Six Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile strains (FT9WT, FT25W, FT26WT, FT109WT, FT134W and CY42WT) were isolated from subtropical streams in China. Comparisons based on 16S rRNA gene sequences showed that the six strains shared similarities of less than 98.1 % with other species within the family Oxalobacteraceae and formed two separately distinct clades in phylogenetic trees. The 16S rRNA gene sequence similarities between strains FT9WT and FT25W, and between strains FT109WT and FT134W were both 99.7 %. The genome sizes of strains FT9WT, FT25W, FT26WT, FT109WT, FT134W and CY42WT were 6.45, 6.45, 6.54, 6.43, 6.52 and 6.74 Mbp with G+C contents of 64.0, 64.0, 63.8, 63.2, 63.2 and 62.5 %, respectively. The calculated pairwise average nucleotide (ANI) values among the six strains and other related species were less than 93.9 %, except that the values were 99.9 % between strains FT9WT and FT25W, 98.2 % between strains FT109WT and FT134W, and 95.0 and 95.1 % between strain FT26WT and strains FT9WT and FT25W, respectively. However, strain FT26WT shared 16S rRNA gene sequence similarities of only 98.3 and 98.2 % with FT9WT and FT25W, respectively. The respiratory quinone of the six strains was determined to be Q-8. The major fatty acids were C16 : 1ω7c, C16 : 0 and C12 : 0. The predominant polar lipids included phosphatidylethanolamine and phosphatidylglycerol. Considering the phenotypic, biochemical, genotypic and ANI data, strains FT9WT and FT25W, and FT109WT and FT134W may belong to the same species, respectively. Although the pairwise ANI values between strain FT26WT and each of strains FT9WT and FT25W were located in the transition region of species demarcation, the dissimilarities among them indicated that strain FT26WT could represent an independent novel species. The reconstructed phylogenomic tree based on a concatenation of 92 core genes showed that the six strains clustered closely with Duganella sacchari Sac-22T and Duganella radicis KCTC 22382T, and supported that these six strains belong to the genus Duganella. The names Duganella albus sp. nov. (type strain FT9WT=GDMCC 1.1637T=KACC 21313T), Duganella aquatilis sp. nov. (type strain FT26WT=GDMCC 1.1641T=KACC 21315T), Duganella pernnla sp. nov. (type strain FT109WT=GDMCC 1.1688T=KACC 21480T) and Duganella levis sp. nov. (type strain CY42WT=GDMCC 1.1673T=KACC 21465T) are proposed.

Ciceribacter ferrooxidans sp. nov., a nitrate-reducing Fe(II)-oxidizing bacterium isolated from ferrous ion-rich sediment.

A nitrate-reducing Fe(II)-oxidizing bacterial strain, F8825T, was isolated from the Fe(II)-rich sediment of an urban creek in Pearl River Delta, China. The strain was Gram-negative, facultative chemolithotrophic, facultative anaerobic, non-spore-forming, and rod-shaped with a single flagellum. Phy-logenetic analysis based on 16S rRNA gene sequencing indicated that it belongs to the genus Ciceribacter and is most closely related to C. lividus MSSRFBL1T (99.4%), followed by C. thiooxidans F43bT (98.8%) and C. azotifigens A.slu09T (98.0%). Fatty acid, polar lipid, respiratory quinone, and DNA G + C content analyses supported its classification in the genus Ciceribacter. Multilocus sequence analysis of concatenated 16S rRNA, atpD, glnII, gyrB, recA, and thrC suggested that the isolate was a novel species. DNA-DNA hybridization and genome sequence comparisons (90.88 and 89.86%, for values of ANIm and ANIb between strains F8825T with MSSRFBL1T, respectively) confirmed that strain F8825T was a novel species, different from C. lividus MSSRFBL1T, C. thiooxidans F43bT, and C. azotifigens A.slu09T. The physiological and biochemical properties of the strain, such as carbon source utilization, nitrate reduction, and ferrous ion oxidation, further supported that this is a novel species. Based on the polyphasic taxonomic results, strain F8825T was identified as a novel species in the genus Ciceribacter, for which the name Ciceribacter ferrooxidans sp. nov. is proposed. The type strain is F8825T (= CCTCC AB 2018196T = KCTC 62948T).

Janthinobacterium violaceinigrum sp. nov., Janthinobacterium aquaticum sp. nov. and Janthinobacterium rivuli sp. nov., isolated from a subtropical stream in China.

Four strains assigned the names FT13WT, FT14W, FT58WT and FT68WT were isolated from a subtropical stream in PR China. All the strains were Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile with flagella. Comparisons based on 16S rRNA gene sequences showed that strains FT13WT, FT14W, FT58WT and FT68WT belonged to genus Janthinobacterium and shared 16S rRNA gene similarities in the range of 98.8-99.7 % with Janthinobacterium lividum DSM 1522T, Janthinobacterium agaricidamnosum DSM 9628T and 'Janthinobacterium svalbardensis JA-1', respectively. The calculated pairwise average nucleotide identity (ANI) values among the genomes of above seven strains were in the range of 79.0-92.2 %, except that the ANI value was 96.8 % between strain FT13WT and FT14W. The respiratory quinone of strains FT13WT, FT14W, FT58WT and FT68WT was determined to be Q-8. The major fatty acids were C16 : 1 ω7c, C16 : 0, C18 : 1 ω7c and C12 : 0. The polar lipids included phosphatidylethanolamine, phosphatidylglycerol and one unidentified phospholipid. The genome sizes of strains FT13WT, FT14W, FT58WT and FT68WT were 6.45, 6.38, 5.73 and 6.37 Mbp with G+C contents of 63.4, 63.7, 61.6 and 63.1 mol%, respectively. Combining phenotypic, biochemical, genotypic and ANI data, strain FT13WT and FT14W should belong to the same species. The four strains were considered to represent three novel species within genus Janthinobacterium, for which the names Janthinobacterium violaceinigrum sp. nov. (type strain FT13WT=GDMCC 1.1638T=KACC 21319T), Janthinobacterium aquaticum sp. nov. (FT58WT=GDMCC 1.1676T=KACC 21468T) and Janthinobacterium rivuli sp. nov. (FT68WT=GDMCC 1.1677T=KACC 21469T) are proposed.

Ciceribacter thiooxidans sp. nov., a novel nitrate-reducing thiosulfate-oxidizing bacterium isolated from sulfide-rich anoxic sediment.

Two facultative chemolithotrophic, nitrate-reducing thiosulfate-oxidizing strains, F43bT and F21, were isolated from the sulfide-rich anoxic sediment of an urban creek in Pearl River Delta, China. Both strains were Gram-negative, facultatively anaerobic, non-spore-forming and rod-shaped with a flagellum. Phylogenetic analyses of 16S rRNA genes and the thrC, recA, glnII and atpD housekeeping genes revealed that the type strain shared high sequence similarities to Ciceribacter lividus MSSRFBL1T, with 98.8, 90.9, 94.8, 95.4 and 96.1 % identity, respectively. In addition, the major isoprenoid quinone (ubiquinone Q-10) and the DNA G+C content (66.0 mol%) of the type strain were similar to those of Ciceribacter lividus MSSRFBL1T. These results strongly support the classification of strains F43bT and F21 into the genus Ciceribacter. However, these strains diverged markedly from strain MSSRFBL1T with respect to several physiological and biochemical properties such as their semi-translucent colonies and nitrate-reducing and simultaneous thiosulfate-oxidizing respiration. Furthermore, the predominant fatty acids of strain F43bT were summed feature 2 (C18 : 1ω9t and/or C18 : 1ω9c and/or C18 : 1ω11t), C14 : 0 3-OH, C18 : 0 and C16 : 0, and its polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidymonomethylethanolamine and an unidentified glycolipid, which represented another two significant differences from strain MSSRFBL1T. Importantly, the DNA-DNA relatedness between strain F43bT and MSSRFBL1T was only 47.7 %. Based on the aforementioned polyphasic taxonomic results, the two isolates are suggested to represent a novel species of the genus Ciceribacter, for which the name Ciceribacterthiooxidans sp. nov. is proposed; the type strain is F43bT (=CCTCC AB 2016062T=KCTC 52231T).