Aromatic amine antioxidants (AAs) and p-phenylenediamines-quinones (PPD-Qs) in e-waste recycling industry park: Occupational exposure and liver X receptors (LXRs) disruption potential.

Recently, evidence of aromatic amine antioxidants (AAs) existence in the dust of the electronic waste (e-waste) dismantling area has been exposed. However, there are limited studies investigating occupational exposure and toxicity associated with AAs and their transformation products (p-phenylenediamines-quinones, i.e., PPD-Qs). In this study, 115 dust and 42 hand wipe samples collected from an e-waste recycling industrial park in central China were analyzed for 19 AAs and 6 PPD-Qs. Notably, the median concentration of ∑6PPD-Qs (1,110 ng/g and 1,970 ng/m2) was significantly higher (p < 0.05, Mann-Whitney U test) than that of ∑6PPDs (147 ng/g and 34.0 ng/m2) in dust and hand wipes. Among the detected analytes, 4-phenylaminodiphenylamine quinone (DPPD-Q) (median: 781 ng/g) and 1,4-Bis(2-naphthylamino) benzene quinone (DNPD-Q) (median: 156 ng/g), were particularly prominent, which were first detected in the e-waste dismantling area. Occupational exposure assessments and nuclear receptor interference ability, conducted through estimated daily intake (EDI) and molecular docking analysis, respectively, indicated significant occupational exposure to PPD-Qs and suggested prioritized Liver X receptors (LXRs) disruption potential of PPDs and PPD-Qs. The study provides the first evidence of considerable levels of AAs and PPD-Qs in the e-waste-related hand wipe samples and underscores the importance of assessing occupational exposure and associated toxicity effects.

Occurrence and Fate of Substituted p-Phenylenediamine-Derived Quinones in Hong Kong Wastewater Treatment Plants.

para-Phenylenediamine quinones (PPD-Qs) are a newly discovered class of transformation products derived from para-phenylenediamine (PPD) antioxidants. These compounds are prevalent in runoff, roadside soil, and particulate matter. One compound among these, N-1,3-dimethylbutyl-n'-phenyl-p-phenylenediamine quinone (6PPD-Q), was found to induce acute mortality of coho salmon, rainbow trout, and brook trout, with the median lethal concentrations even lower than its appearance in the surface and receiving water system. However, there was limited knowledge about the occurrence and fate of these emerging environmental contaminants in wastewater treatment plants (WWTPs), which is crucial for effective pollutant removal via municipal wastewater networks. In the current study, we performed a comprehensive investigation of a suite of PPD-Qs along with their parent compounds across the influent, effluent, and biosolids during each processing unit in four typical WWTPs in Hong Kong. The total concentrations of PPDs and PPD-Qs in the influent were determined to be 2.7-90 and 14-830 ng/L. In the effluent, their concentrations decreased to 0.59-40 and 2.8-140 ng/L, respectively. The median removal efficiency for PPD-Qs varied between 53.0 and 91.0% across the WWTPs, indicating that a considerable proportion of these contaminants may not be fully eliminated through the current processing technology. Mass flow analyses revealed that relatively higher levels of PPD-Qs were retained in the sewage sludge (20.0%) rather than in the wastewater (16.9%). In comparison to PPDs, PPD-Qs with higher half-lives exhibited higher release levels via effluent wastewater, which raises particular concerns about their environmental consequences to aquatic ecosystems.

Determination of Anthraquinone-Tagged Amines Using High-Performance Liquid Chromatography with Online UV Irradiation and Luminol Chemiluminescence Detection.

Quinones are frequently used as derivatization reagents in HPLC analysis to improve detection sensitivity. In the present study, a simple, sensitive, and selective chemiluminescence (CL) derivatization strategy for biogenic amines, prior to their HPLC-CL analysis, was developed. The novel CL derivatization strategy was established based on using anthraquinone-2-carbonyl chloride as derivatizing agent for amines and then using the unique property of the quinones' moiety to generate reactive oxygen species (ROS) in response to UV irradiation. Typical amines such as tryptamine and phenethylamine were derivatized with anthraquinone-2-carbonyl chloride and then injected into an HPLC system equipped with an online photoreactor. The anthraquinone-tagged amines are separated and then UV-irradiated when they pass through a photoreactor to generate ROS from the quinone moiety of the derivative. Tryptamine and phenethylamine can be determined by measuring the chemiluminescence intensity produced by the reaction of the generated ROS with luminol. The chemiluminescence disappears when the photoreactor is turned off, suggesting that ROS are no longer generated from the quinone moiety in the absence of UV irradiation. This result indicates that the generation of ROS could be controlled by turning the photoreactor on and off. Under the optimized conditions, the limits of detection for tryptamine and phenethylamine were 124 and 84 nM, respectively. The developed method is successfully applied to determine the concentrations of tryptamine and phenethylamine in wine samples.

A rare isoflavone-quinone and a new flavanone from the roots of Dalbergia stipulacea Roxb.

Two previously undescribed compounds, namely dalpulapans F and G (1 and 2), along with 11 known compounds were isolated from the MeOH crude extract of the roots of Dalbergia stipulacea. Dalpulapan F was found as a rare isoflavone-quinone derivative. Their structures and absolute configurations were supported by extensive spectroscopic data analysis, including 1 D and 2 D NMR, HRESIMS data, specific rotation data, and comparison of the experimental and calculated ECD data. Cytotoxicity evaluation of the isolated compounds against HepG2 and KKU-M156 cell lines revealed that isoflavonoid 9 and rotenoid 13 exhibited the most activity against the two cell lines.

A cell-based evaluation of human tyrosinase-mediated metabolic activation of leukoderma-inducing phenolic compounds.

BACKGROUND: Chemical leukoderma is a skin depigmentation disorder induced through contact with certain chemicals, most of which have a p-substituted phenol structure similar to the melanin precursor tyrosine. The tyrosinase-catalyzed oxidation of phenols to highly reactive o-quinone metabolites is a critical step in inducing leukoderma through the production of melanocyte-specific damage and immunological responses. OBJECTIVE: Our aim was to find an effective method to evaluate the formation of o-quinone by human tyrosinase and subsequent cellular reactions. METHODS: Human tyrosinase-expressing 293T cells were exposed to various phenolic compounds, after which the reactive o-quinones generated were identified as adducts of cellular thiols. We further examined whether the o-quinone formation induces reductions in cellular GSH or viability. RESULTS: Among the chemicals tested, all 7 leukoderma-inducing phenols/catechol (rhododendrol, raspberry ketone, monobenzone, 4-tert-butylphenol, 4-tert-butylcatechol, 4-S-cysteaminylphenol and p-cresol) were oxidized to o-quinone metabolites and were detected as adducts of cellular glutathione and cysteine, leading to cellular glutathione reduction, whereas 2-S-cysteaminylphenol and 4-n-butylresorcinol were not. In vitro analysis using a soluble variant of human tyrosinase revealed a similar substrate-specificity. Some leukoderma-inducing phenols exhibited tyrosinase-dependent cytotoxicity in this cell model and in B16BL6 melanoma cells where tyrosinase expression was effectively modulated by siRNA knockdown. CONCLUSION: We developed a cell-based metabolite analytical method to detect human tyrosinase-catalyzed formation of o-quinone from phenolic compounds by analyzing their thiol-adducts. The detailed analysis of each metabolite was superior in sensitivity and specificity compared to cytotoxicity assays for detecting known leukoderma-inducing phenols, providing an effective strategy for safety evaluation of chemicals.

Pseudalkalibacillus salsuginis sp. nov., a novel salt-tolerant bacterium isolated from a saline lake sediment.

A salt-tolerant bacterium, designated strain EGI L200015T, was isolated from saline lake sediment in Xinjiang Uygur Autonomous Region, PR China. The taxonomic position of the isolate was determined using polyphasic taxonomic analysis and phylogenomic analysis. Phylogenetic analysis and 16S rRNA gene sequence similarities indicated that EGI L200015T formed a distinct clade with Pseudalkalibacillus berkeleyi KCTC 12718T with sequence identity of 98.3%. The novel isolate could be distinguished from species of the genus Pseudalkalibacillus by its distinct phenotypic, physiological and genotypic characteristics. Cells of EGI L200015T were aerobic, Gram-stain-positive, non-motile and rod-shaped. Optimal growth conditions for EGI L200015T occurred on marine agar 2216 at pH 8.0 at 30 °C. The major respiratory quinone was MK-7, while the major fatty acids (> 10 %) were anteiso-C15 : 0, iso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The detected polar lipids of included diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. On the basis of the genome sequence data, the DNA G+C content of EGI L200015T was 41.6 %. On the basis of the phenotypic, physiological, genotypic and phylogenetic data, strain EGI L200015T represents a novel species of the genus Pseudalkalibacillus, for which the name Pseudalkalibacillus salsuginis sp. nov. is proposed. The type strain of the proposed novel isolate is EGI L200015T (= KCTC 43363T = CGMCC 1.19260T).

Air monitoring of tire-derived chemicals in global megacities using passive samplers.

Pollution from vehicle tires has received world-wide research attention due to its ubiquity and toxicity. In this study, we measured various tire-derived contaminants semi-quantitatively in archived extracts of passive air samplers deployed in 18 major cities that comprise the Global Atmospheric Passive Sampling (GAPS) Network (GAPS-Megacities). Analysis was done on archived samples, which represent one-time weighted passive air samples from each of the 18 monitoring sites. The target analytes included cyclic amines, benzotriazoles, benzothiazoles, and p-phenylenediamine (PPD) derivatives. Of the analyzed tire-derived contaminants, diphenylguanidine was the most frequently detected analyte across the globe, with estimated concentrations ranging from 45.0 pg/m3 in Beijing, China to 199 pg/m3 in Kolkata, India. The estimated concentrations of 6PPD-quinone and total benzothiazoles (including benzothiazole, 2-methylthio-benzothiazole, 2-methyl-benzothiazole, 2-hydroxy-benzothiazole) peaked in the Latin American and the Caribbean region at 1 pg/m3 and 100 pg/m3, respectively. In addition, other known tire-derived compounds, such as hexa(methoxymethyl)melamine, phenylguanidine, and various transformation products of 6PPD, were also monitored and characterized semi-quantitatively or qualitatively. This study presents some of the earliest data on airborne concentrations of chemicals associated with tire-wear and shows that passive sampling is a viable techniquefor monitoring airborne tire-wear contamination. Due to the presence of many tire-derived contaminants in urban air across the globe as highlighted by this study, there is a need to determine the associated exposure and toxicity of these chemicals to humans.

Biomimetic Recognition of Quinones in Water by an Endo-Functionalized Cavity with Anthracene Sidewalls.

Selective molecular recognition in water is the foundation of numerous biological functions but is a challenge for most synthetic hosts. We employ the concept of endo-functionalized cavity and the strategy of simultaneous construction to address this issue. The concept and the strategy were demonstrated in the construction of a biomimetic host for selectively recognizing quinones in water. The host was synthesized by joining two pieces of bent anthracene dimer through amide bond formation, affording a deep hydrophobic cavity and inward-directing hydrogen bonding sites. The host can recognize quinones over their close analogues in water, and its association affinity to p-benzoquinone is the highest among all the known hosts and is even comparable to that of the bioreceptor. The binding with an anthraquinone reaches nanomolar affinity. Shielded hydrogen bonding, C-H⋅⋅⋅π, and charge transfer interactions, and the hydrophobic effect are responsible for the high binding affinity and selectivity.

Chemical profiling of Zilong Jin tablets using ultra high performance liquid chromatography-quadrupole/orbitrap high resolution mass spectrometry.

Zilongjin tablets as a traditional Chinese medicine are widely used for primary lung cancer patients with deficiency of "qi " and "blood " syndrome undergoing chemotherapy. It is a compound preparation that consists of eight herbs. To clarify the chemical profiling of Zilong Jin tablets rapidly, a feasible and accurate strategy was developed by the ultra high performance liquid chromatography-quadrupole/orbitrap high resolution mass spectrometry. According to the accurate mass and fragment ion information provided by high resolution mass spectrometry, the compounds were reasonably identified. In total, 74 compounds were characterized, including 20 flavonoids, 14 quinones, 15 organic acids, 6 phthalide compounds, and 19 other compounds. Among them, 34 major compounds were unambiguously confirmed by comparing with reference standards. This study could provide an important scientific basis for further research on quality control, pharmacokinetics and pharmacodynamics, and clinical application of Zilong Jin tablets.

The signaling role of extracellular ATP in co-culture of Shiraia sp. S9 and Pseudomonas fulva SB1 for enhancing hypocrellin A production.

BACKGROUND: Adenosine 5'-triphosphate (ATP) plays both a central role as an intracellular energy source, and a crucial extracellular signaling role in diverse physiological processes of animals and plants. However, there are less reports concerning the signaling role of microbial extracellular ATP (eATP). Hypocrellins are effective anticancer photodynamic therapy (PDT) agents from bambusicolous Shiraia fungi. The co-culture of Shiraia sp. S9 and a bacterium Pseudomonas fulva SB1 isolated from Shiraia fruiting bodies was established for enhanced hypocrellin A (HA) production. The signaling roles of eATP to mediate hypocrellin biosynthesis were investigated in the co-culture. RESULTS: The co-culture induced release of eATP at 378 nM to the medium around 4 h. The eATP release was interdependent on cytosolic Ca2+ concentration and reactive oxygen species (ROS) production, respectively. The eATP production could be suppressed by the Ca2+ chelator EGTA or abolished by the channel blocker La3+, ROS scavenger vitamin C and NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI). The bacterium-induced H2O2 production was strongly inhibited by reactive blue (RB), a specific inhibitor of membrane purinoceptors, but dependent on the induced Ca2+ influx in the co-culture. On the other hand, the application of exogenous ATP (exATP) at 10-300 µM to Shiraia cultures also promoted fungal conidiation and HA production, both of which were blocked effectively by the purinoceptor inhibitors pyridoxalphosphate-6-azophenyl-2', 4'-disulfonic acid (PPADS) and RB, and ATP hydrolase apyrase. Both the induced expression of HA biosynthetic genes and HA accumulation were inhibited significantly under the blocking of the eATP or Ca2+ signaling, and the scavenge of ROS in the co-culture. CONCLUSIONS: Our results indicate that eATP release is an early event during the intimate bacterial-fungal interaction and eATP plays a signaling role in the bacterial elicitation on fungal metabolites. Ca2+ and ROS are closely linked for activation of the induced ATP release and its signal transduction. This is the first report on eATP production in the fungal-bacterial co-culture and its involvement in the induced biosynthesis of fungal metabolites.

The Analysis of Phenolic Compounds in Walnut Husk and Pellicle by UPLC-Q-Orbitrap HRMS and HPLC.

Husk and pellicle as the agri-food waste in the walnut-product industry are in soaring demand because of their rich polyphenol content. This study investigated the differential compounds related to walnut polyphenol between husk and pellicle during fruit development stage. By using ultra-high performance liquid chromatography-quadrupole-orbitrap (UHPLC-Q-Orbitrap), a total of 110 bioactive components, including hydrolysable tannins, flavonoids, phenolic acids and quinones, were tentatively identified, 33 of which were different between husk and pellicle. The trend of dynamic content of 16 polyphenols was clarified during walnut development stage by high-performance liquid chromatography (HPLC). This is the first time to comprehensive identification of phenolic compounds in walnut husk and pellicle, and our results indicated that the pellicle is a rich resource of polyphenols. The dynamic trend of some polyphenols was consistent with total phenols. The comprehensive characterization of walnut polyphenol and quantification of main phenolic compounds will be beneficial for understanding the potential application value of walnut and for exploiting its metabolism pathway.

Implications of Fagopyrin Formation In Vitro by UV Spectroscopic Analysis.

The present work aims at studying the possible biosynthesis of fagopyrin in buckwheat plants with an attempt to address the existing gaps. The developed method of differential spectrophotometry can be used for identification of naphthodianthrones fagopyrins. It was found that in the vegetative mass of buckwheat plants, fagopyrin precursor-2-(piperidine-2-yl)-emodindianthron could be present. As fagopyrin can be produced by light effect, the temperature factor may influence the formation of protofagopyrin in vitro. An optimum temperature range was estimated for protofagopyrin formation. A possible fagopyrin biosynthesis under in vitro conditions was suggested.

Sphingomonas parva sp. nov., isolated from soil in Jeju Island.

A Gram staining-negative, yellow-colored, rod-shaped, non-motile and aerobic, designated strain 17J27-24T was isolated from a soil sample in Korea. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 17J27-24T was related to the members of the family Sphingomonadaceae and formed a distinct monophyletic cluster within the genus Sphingomonas with Sphingomonas deserti (98.3% 16S rRNA gene sequence similarity). Growth was observed at 30 °C (optimum), at pH 7.0 (optimum), and in the absence of NaCl (%). The predominant cellular fatty acids were summed feature 8 (18:1 ω7c and/or 18:1 ω6c) and C17:1 ω6c. The major respiratory quinone was Q10. The polar lipids profile comprised of diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and sphingoglycolipid (SGL). The DNA G + C content was 77.8 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridisation (dDDH) values between 17J27-24T and its phylogenetically closest Sphingomonas deserti (KCTC 62411T) were below the established cut-off < 94% (ANI) and < 70% (dDDH) for species delineation. Moreover, the results of the polyphasic approach confirmed that strain 17J27-24T represents a novel species of the genus Sphingomonas within the family Sphingomonadaceae, for which the name Sphingomonas parva sp. nov. is proposed. The type strain of this species is 17J27-24T (= KCTC 62208T = JCM 3896T). An emended description of the species Sphingomonas parva is provided.

UPLC-ESI-MS/MS-Based Widely Targeted Metabolomics Analysis of Wood Metabolites in Teak (Tectona grandis).

The properties of teak wood, such as natural durability and beautiful color, are closely associated with wood extractives. In order to further understand the performance differences between teak heartwood and sapwood, we analyzed the chemical components of extractives from 12 wood samples using an ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS)-based metabolomics approach. In total, 691 metabolites were identified, and these were classified into 17 different categories. Clustering analysis and principal component analysis of metabolites showed that heartwood samples could be clearly separated from sapwood samples. Differential metabolite analysis revealed that the levels of primary metabolites, including carbohydrates, amino acids, lipids, and nucleotides, were significantly lower in the heartwood than in the sapwood. Conversely, many secondary metabolites, including flavonoids, phenylpropanoids, and quinones, had higher levels in the heartwood than in the sapwood. In addition, we detected 16 specifically expressed secondary metabolites in the heartwood, the presence of which may correlate with the durability and color of teak heartwood. Our study improves the understanding of differential metabolites between sapwood and heartwood of teak and provides a reference for the study of heartwood formation.

A rapid analysis method of safflower (Carthamus tinctorius L.) using combination of computer vision and near-infrared.

The quality of safflower (Carthamus tinctorius L.) in the market is uneven due to the problems of dyeing and adulteration of safflower, and there is no perfect standard for the classification of quality grade of safflower at present. In this study, computer vision (CV) and near-infrared (NIR) were combined to realize the rapid and nondestructive analysis of safflower. First, the partial least squares discrimination analysis (PLS-DA) model was used to qualitatively identify the dyed safflower from 150 samples. Then the partial least squares (PLS) model was used for quantitative analysis of the hydroxy safflower yellow pigment A (HSYA) and water extract of undyed safflower. Herein, the discrimination rate of PLS-DA model reached 100%, and the residual predictive deviation (RPD) values of the PLS models for HSYA and water extract were 2.5046 and 5.6195, respectively. It indicated that the rapid analysis method combining CV and NIR was reliable, and its results can provide important reference for the formulation of safflower quality classification standards in the market.

Acinetobacter pullicarnis sp. nov. isolated from chicken meat.

A novel bacterial strain, named S23T, was isolated from chicken meat of local market in Korea. Cells were Gram-negative, milky-yellow colored, non-motile and coccobacillus. The strain was obligate aerobic and catalase-positive, oxidase-negative, optimum growth temperature and pH were 25 °C and pH 7.0, respectively. On the basis of 16S rRNA gene sequence analysis, strain S23T belongs to the genus Acinetobacter and is most closely related to Acinetobacter defluvii KCTC 52503 T (97.40%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) value between strain S23T and its closet phylogenetic neighbors was below 76% and 17%, respectively. The G + C content of genomic DNA of strain S23T was 41.53 mol%. The major respiratory quinone was Q-9. The major cellular fatty acids were summed feature 3 (comprising C16:1ω7c and/or C16:1ω6c), C18:1ω9c, and C16:0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanol-amine, and phosphatidylserine. The ANI and dDDH results and results of the genotypic analysis in combination with chemotaxonomic and physiological data demonstrated that strain S23T represented a novel species within the genus Acinetobacter, for which the name Acinetobacter pullicarnis sp. nov. is proposed. The strain type is S23T (= KACC 19921 T = JCM 33150 T).

Corallincola spongiicola sp. nov., isolated from sponge.

A gram-negative, motile, strictly aerobic, and rod-shaped bacterium designated 176GS2-150T was isolated from the sponge Hymeniacidon sinapium. The taxonomic position of the novel isolate was confirmed using the polyphasic approach. Strain 176GS2-150T grew well at 25 °C on marine agar. Based on its 16S rRNA gene sequence, we showed that strain 176GS2-150T belongs to the family Psychromonadaceae and class Gammaproteobacteria and is related to Corallincola platygyrae JLT2006T (96.84% sequence similarity). The G + C content of the genomic DNA was 49.0 mol%. The assembled draft genome of strain 176GS2-150T was 4.2 Mbp and consisted of 14 contigs. The major respiratory quinone was Q-8, and the major fatty acids were summed feature 3 (comprising C16 :1ω6c and/or C16:1ω7c), summed feature 8 (comprising C18 :1ω7c and/or C18:1ω6c), C17:0 iso, C16:0, and C15:0 iso. The polar lipids were phosphatidylglycerol, phosphatidylethanolamine, 3 unidentified phospholipids, and 1 unidentified polar lipid. On the basis of the genotypic and phenotypic characteristics, strain 176GS2-150T can be placed as a new species within the genus Corallincola; the name Corallincola spongiicola sp. nov. has been proposed, with type strain 176GS2-150T (= KACC 19890T = LMG 31317T).

Effects of plant growth regulator application on the malting quality of barley.

BACKGROUND: Lodging can negatively affect yield and quality of barley grain. Synthetic plant growth regulators (PGRs) reduce lodging by producing shorter, thicker, and stronger stems. However, the impact of applying PGRs on malting performance of barley is not known. The objective of this work was to assess the effect of application of three PGRs (ethephon, chlormequat chloride, and trinexapac-ethyl) in combination with different seeding rates on the malting quality of barley grown in several locations and years in western Canada. RESULTS: The kernel weight in PGR-treated barley was reduced by 1.7% to 6.5% compared with the nontreated grain. Application of PGRs had no effect on the concentration of proteins and germination energy. Seeding rates significantly affected kernel weight, protein content, and germination index (GI), but no interactions between PGRs and seeding rates were observed. The smaller kernels of ethephon- and trinexapac-treated barley showed good hydration and grain modification during malting, as indicated by high levels of starch-converting enzymes, high Kolbach indices, and low levels of wort ß-glucans. Overall, the fine extract of malt from PGR-treated barley was slightly lower than that of the control malt; however, the extract reduction was statistically significant only for chlormequat- and trinexapac-treated barley. CONCLUSIONS: The application of PGRs had significant effects on kernel plumpness and kernel weight, but the effects of PGR application on the malting quality were generally small and insignificant. The decision of PGRs application on malting barley needs to be considered in combination with potential benefits of PGRs in mitigating lodging and their effects on the agronomic performance of barley. © Her Majesty the Queen in Right of Canada 2019.

Mutational analysis of the flavinylation and binding motifs in two protein targets of the flavin transferase ApbE.

Many flavoproteins belonging to three domain types contain an FMN residue linked through a phosphoester bond to a threonine or serine residue found in a conserved seven-residue motif. The flavinylation reaction is catalyzed by a specific enzyme, ApbE, which uses FAD as a substrate. To determine the structural requirements of the flavinylation reaction, we examined the effects of single substitutions in the flavinylation motif of Klebsiella pneumoniae cytoplasmic fumarate reductase on its modification by its own ApbE in recombinant Escherichia coli cells. The replacement of the flavin acceptor threonine with alanine completely abolished the modification reaction, whereas the replacements of conserved aspartate and serine had only minor effects. Effects of other substitutions, including replacing the acceptor threonine with serine, (a 10-55% decrease in the flavinylation degree) pinpointed important glycine and alanine residues and suggested an excessive capacity of the ApbE-based flavinylation system in vivo. Consistent with this deduction, drastic replacements of conserved leucine and threonine residues in the binding pocket that accommodates FMN residue still allowed appreciable flavinylation of the NqrC subunit of Vibrio harveyi Na+-translocating NADH:quinone oxidoreductase, despite a profound weakening of the isoalloxazine ring binding and an increase in its exposure to solvent.

Flavobacterium zhairuonensis sp. nov., a gliding bacterium isolated from marine sediment of the East China Sea.

A yellow pigmented, Gram-stain-negative, aerobic bacterium designated A5.7T was studied to evaluate the taxonomic position following the modern polyphasic approach. The strain was isolated from sediments near Zhairuo Island, which is situated in the East China Sea. Cells were non-spore forming rods without flagella but showed motility by gliding. Growth was observed at 15-35°C (optimum 28°C), pH 6.0-9.0 (optimum pH 6.5) and 0-2% (w/v) NaCl (optimum 0-0.5%) in LB broth. The major respiratory quinone of A5.7T was menaquinone 6. The major polar lipid of A5.7T was phosphatidylethanolamine and the predominant fatty acids (> 5%) were iso-C15:0, iso-C17:0 3-OH, C15:1ω6c, iso-C15:0 3-OH, iso-C15:1 G, summed feature 3 (C16:1ω7c and/or C16:1ω6c) and summed feature 9 (iso-C17:1ω9c and/or C16:010-methyl). Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate belongs to the genus Flavobacterium and shares the highest sequence similarities with Flavobacterium sharifuzzamanii A7.6T (98.5%), Flavobacterium tistrianum GB 56.1T (98.3%), Flavobacterium nitrogenifigens NXU-44T (97.8%), Flavobacterium anhuiense D3T (97.6%), Flavobacterium ginsenosidimutans THG 01T (97.6%), and Flavobacterium foetidum CJ42T (97.6%). Digital DNA-DNA hybridization and average nucleotide identity values between the strain and its closest phylogenetic neighbors showed the ranges from 19.6 to 34.1% and 73.7 to 87.9%, respectively. Therefore, based on polyphasic characteristics, strain A5.7T represents a novel species of the genus Flavobacterium for which the name Flavobacterium zhairuonensis sp. nov. is proposed. The type strain is A5.7T (= KCTC 62406T = MCCC 1K03494T).