Expression of Staphylococcus aureus translation elongation factor P is regulated by a stress-inducible promotor.

Translation elongation factor P, expressed by the efp gene, is a conserved protein closely related to bacterial virulence and environmental stress regulation responses, however, little is known about the efp gene expression regulations. Here, the strain of Staphylococcus aureus subsp. aureus NCTC 8325 was taken as the research object and cultured under different conditions, including different culture temperatures, pH, and antibiotics, to study the expression of the efp gene in S. aureus by qRT-PCR, the results showed that the expression of the efp gene is upregulated under high temperature (40 °C), acidic (pH 5.4) or alkaline (pH 9.4) culture conditions, but upregulated early and downregulated later under the conditions of 0.5 MIC antibiotics (chloramphenicol at the final concentration of 2 µg/mL and vancomycin at the final concentration of 0.25 µg/mL), indicating that the efp promoter in S. aureus is inducible. The efp promoter sequence and structure in S. aureus were predicted by bioinformatics methods, and the predicted promoter was validated by constructing a promoter-probe vector and a series of promoter mutants, the results showed that the efp promoter sequence in S. aureus, named Pro, located in 1,548,179-1,548,250 of the S. aureus genome (NC_007795.1), and the sequence of - 10 element is CCTTATAGT, - 35 element is TTTACT. The results above could lay a foundation for screening transcription factors involved in the expression of the efp gene and then exploring the transcriptional regulation mechanism of EF-P in S. aureus.

Methylsiloxanes from Vehicle Emissions Detected in Aerosol Particles.

Methylsiloxanes have gained growing attention as emerging pollutants due to their toxicity to organisms. As man-made chemicals with no natural source, most research to date has focused on volatile methylsiloxanes from personal care or household products and industrial processes. Here, we show that methylsiloxanes can be found in primary aerosol particles emitted by vehicles based on aerosol samples collected in two tunnels in São Paulo, Brazil. The aerosol samples were analyzed with thermal desorption-proton transfer reaction-mass spectrometry (TD-PTR-MS), and methylsiloxanes were identified and quantified in the mass spectra based on the natural abundance of silicon isotopes. Various methylsiloxanes and derivatives were found in aerosol particles from both tunnels. The concentrations of methylsiloxanes and derivatives ranged 37.7-377 ng m-3, and the relative fractions in organic aerosols were 0.78-1.9%. The concentrations of methylsiloxanes exhibited a significant correlation with both unburned lubricating oils and organic aerosol mass. The emission factors of methylsiloxanes averaged 1.16 ± 0.59 mg kg-1 of burned fuel for light-duty vehicles and 1.53 ± 0.37 mg kg-1 for heavy-duty vehicles. Global annual emissions of methylsiloxanes in vehicle-emitted aerosols were estimated to range from 0.0035 to 0.0060 Tg, underscoring the significant yet largely unknown potential for health and climate impacts.

Sphingomonas caeni sp. nov., a phenolic acid-degrading bacterium isolated from activated sludge.

A Gram-stain-negative, rod-shaped, polar flagellated or stalked and non-spore-forming bacterium, designated LB-2T, was isolated from activated sludge. Growth was observed at 20-30 °C (optimum 28 °C), pH 6.0-8.0 (optimum pH 7.0) and salinity of 0-0.5% (w/v; optimum 0.5%). Phylogenetic analysis based on the 16S rRNA gene indicated that strain LB-2T belongs to the genus Sphingomonas and showed the highest sequence similarity (96.7%) and less than 96.7% similarities to other type strains. The genome size of strain LB-2T was 4.10 Mb, with 66.8 mol% G + C content. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strains LB-2T and S. canadensis FWC47T were 77.8% and 21%, respectively. The predominant cellular fatty acids were summed feature 8 (C18:1ω7c and/or C18 : 1ω6c) and C16:0. The major polar lipids were aminolipid, glycolipid, sphingoglycolipid, phosphatidylcholine, phosphatidylglycerol, four unidentified lipids, glycophospholipid, phosphatidylethanolamine and diphosphatidylglycerol. The predominant respiratory quinone was Q-10 and the major polyamine was sym-homospermidine. On the basis of phenotypic, genotypic and phylogenetic evidences, strain LB-2T represents a novel species in the genus Sphingomonas, for which the name Sphingomonas caeni sp. nov. is proposed. The type strain is LB-2T (GDMCC 1.3630T = NBRC 115,102T).

Modified you-only-look-once model for joint source detection and azimuth estimation in a multi-interfering underwater acoustic environment.

The you-only-look-once (YOLO) model identifies objects in complex images by framing detection as a regression problem with spatially separated boundaries and class probabilities. Object detection from complex images is somewhat similar to underwater source detection from acoustic data, e.g., time-frequency distributions. Herein, YOLO is modified for joint source detection and azimuth estimation in a multi-interfering underwater acoustic environment. The modified you-only-look-once (M-YOLO) input is a frequency-beam domain (FBD) sample containing the target and multi-interfering spectra at different azimuths, generated from the received data of a towed horizontal line array. M-YOLO processes the whole FBD sample using a single-regression neural network and directly outputs the target-existence probability and spectrum azimuth. Model performance is assessed on both simulated and at-sea data. Simulation results reveal the strong robustness of M-YOLO toward different signal-to-noise ratios and mismatched ocean environments. As tested on the data collected in an actual multi-interfering environment, M-YOLO achieved near-100% target detection and a root mean square error of 0.54° in azimuth estimation.

Chemical signature and fractionation of trace elements in fine particles from anthropogenic and natural sources.

The health effects of trace metal elements in atmospheric fine particulate matter (PM2.5) are widely recognized, however, the emission factor profiles and chemical fractionation of metal elements in different sources were poorly understand. In this study, sixteen metal elements, including Cd, Pb, V, Zn, Ba, Sb, As, Fe, Sr, Cr, Rb, Co, Mn, Cu, Ni and Sn from biomass burning, bituminite and anthracite combustion, as well as dust, were quantified. The results show different emission sources were associated with distinct emission profiles, holding important implications for source apportionment of ambient particulate metals. Specifically, Fe was the dominant metal species (28-1922 mg/kg) for all samples, and was followed by different metals for different samples. For dust, Mn (39.9 mg/kgdust) had the second-highest emission factor, while for biomass burning, it was Cr and Ba (7.5 and 7.4 mg/kgbiomass, respectively). For bituminous coal combustion, the emission factor of Zn and Ba was 6.2 and 6.0 mg/kgbituminous, respectively, while for anthracite combustion the corresponding emission factor was 5.6 and 4.3 mg/kganthracite, respectively. Moreover, chemical fractionation (i.e., the exchangeable, reducible fraction, oxidizable, and residual fraction) and the bioavailability index (BI) values of the metal elements from different sources were further investigated to reveal the link between different emission sources and the potential health risk. The findings from this study hold important implications for source apportionment and source-specific particulate metal-associated health effects.

Brown Carbon in Primary and Aged Coal Combustion Emission.

Smog chamber experiments were conducted to characterize the light absorption of brown carbon (BrC) from primary and photochemically aged coal combustion emissions. Light absorption was measured by the UV-visible spectrophotometric analysis of water and methanol extracts of filter samples. The single-scattering albedo at 450 nm was 0.73 ± 0.10 for primary emissions and 0.75 ± 0.13 for aged emissions. The light absorption coefficient at 365 nm of methanol extracts was higher than that of water extracts by a factor of 10 for primary emissions and a factor of 7 for aged emissions. This suggests that the majority of BrC is water-insoluble even after aging. The mass absorption efficiency of this BrC (MAE365) for primary OA (POA) was dependent on combustion conditions, with an average of 0.84 ± 0.54 m2 g-1, which was significantly higher than that for aged OA (0.24 ± 0.18 m2 g-1). Secondary OA (SOA) dominated aged OA and the decreased MAE365 after aging indicates that SOA is less light absorbing than POA and/or that BrC is bleached (oxidized) with aging. The estimated MAE365 of SOA (0.14 ± 0.08 m2 g-1) was much lower than that of POA. A comparison of MAE365 of residential coal combustion with other anthropogenic sources suggests that residential coal combustion emissions are among the strongest absorbing BrC organics.

Deep transfer learning for underwater direction of arrival using one vector sensor.

A deep transfer learning (DTL) method is proposed for the direction of arrival (DOA) estimation using a single-vector sensor. The method involves training of a convolutional neural network (CNN) with synthetic data in source domain and then adapting the source domain to target domain with available at-sea data. The CNN is fed with the cross-spectrum of acoustical pressure and particle velocity during the training process to learn DOAs of a moving surface ship. For domain adaptation, first convolutional layers of the pre-trained CNN are copied to a target CNN, and the remaining layers of the target CNN are randomly initialized and trained on at-sea data. Numerical tests and real data results suggest that the DTL yields more reliable DOA estimates than a conventional CNN, especially with interfering sources.

Water-Insoluble Organics Dominate Brown Carbon in Wintertime Urban Aerosol of China: Chemical Characteristics and Optical Properties.

The chromophores responsible for light absorption in atmospheric brown carbon (BrC) are not well characterized, which hinders our understanding of BrC chemistry, the links with optical properties, and accurate model representations of BrC to global climate and atmospheric oxidative capacity. In this study, the light absorption properties and chromophore composition of three BrC fractions of different polarities were characterized for urban aerosol collected in Xi'an and Beijing in winter 2013-2014. These three BrC fractions show large differences in light absorption and chromophore composition, but the chromophores responsible for light absorption are similar in Xi'an and Beijing. Water-insoluble BrC (WI-BrC) fraction dominates the total BrC absorption at 365 nm in both Xi'an (51 ± 5%) and Beijing (62 ± 13%), followed by a humic-like fraction (HULIS-BrC) and high-polarity water-soluble BrC. The major chromophores identified in HULIS-BrC are nitrophenols and carbonyl oxygenated polycyclic aromatic hydrocarbons (OPAHs) with 2-3 aromatic rings (in total 18 species), accounting for 10% and 14% of the light absorption of HULIS-BrC at 365 nm in Xi'an and Beijing, respectively. In comparison, the major chromophores identified in WI-BrC are PAHs and OPAHs with 4-6 aromatic rings (in total 16 species), contributing 6% and 8% of the light absorption of WI-BrC at 365 nm in Xi'an and Beijing, respectively.

Rudanella paleaurantiibacter sp. nov., Isolated from Activated Sludge.

A Gram-stain-negative, orange-colored bacterium, designated HX-22-17T, was isolated from activated sludge of an agricultural chemical plant in Maanshan, Anhui province, China (118° 52' E 31° 68' N). The strain was strictly aerobic, non-endospore forming, non-motile, and ellipse. Growth of the strain was observed at 16-42 °C (optimum between 25 and 30 °C) at pH 6.0-9.0 (optimum at pH 7.0) and with 0-6.0% (w/v) NaCl (optimum at 1.0%). 16S rRNA gene sequence analysis showed that the strain was most closely related to Rudanella lutea KACC 12603T (99.5% similarity). The predominant cellular fatty acids were summed feature 3 (C16:1ω7c and/or C16:1ω6c), iso-C15:0, and anteiso-C15:0. The major polar lipids included posphatidylethanolamine (PE), aminolipid (AL), and phospholipids (PL). The genomic DNA G+C content of the strain was 54.1 mol%. The ANI and dDDH values obtained between the genomes of HX-22-17T and R. lutea KACC 12603T were 89.3% and 39.3%, respectively. The phenotypic, chemotaxonomic, and genotypic data clearly showed that strain HX-22-17T represents a novel species of the genus Rudanella, for which the name R. paleaurantiibacter sp. nov. is proposed. The type strain is HX-22-17T (=KCTC 72656T = CCTCC AB 2019347T).

Extensimonas perlucida sp. nov., a Novel Bacterium Isolated from Sludge.

A bacterium, designated HX2-24 T, was isolated from activated sludge treating pesticide-manufacturing wastewater. Colonies of the strain on nutrient agar were circular, transparent, and colorless. Strain HX2-24 T shared 98.1% 16S rRNA gene sequence similarity with Extensimonas vulgaris S4T, and less than 97% similarities with other type strains. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain formed a clade with E. vulgaris S4T. The major cellular fatty acids were C16:0, summed feature 3 (C16:1ω7c and/or C16:1ω6c) and C17:0 cyclo, the major polar lipids were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), aminophospholipid (APL), glycophospholipid (GPL), and aminoglycolipid (AGL). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between HX2-24 T and E. vulgaris S4T were 92% and 41%, respectively. The G + C content of strain HX2-24 T was 64.4 mol%. Thus, based on the phenotypic, chemotaxonomic, and genotypic characteristics, strain HX2-24 T represents a novel species in the genus Extensimonas, for which the name Extensimonas perlucida HX2-24 T sp. nov. is proposed. The type strain is HX2-24 T (= KCTC 72472 T = CCTCC AB 2019178 T).

Anti-Inflammatory Effects of Neochlorogenic Acid Extract from Mulberry Leaf (Morus alba L.) Against LPS-Stimulated Inflammatory Response through Mediating the AMPK/Nrf2 Signaling Pathway in A549 Cells.

Neochlorogenic acid (nCGA) is a phenolic compound isolated from mulberry leaf (Morus alba L.), which possesses multiple pharmacological activities containing antioxidant and anti-inflammatory effects. However, the role of nCGA in the treatment of acute pneumonia and the underlying molecular mechanism are still unclear. Hence, the aim of study is to investigate the anti-inflammatory properties of nCGA on LPS-stimulated inflammation in A549 cells. In the present study, results reported that nCGA without cytotoxicity significantly reduced the production of TNF-α, IL-6, and NO, and further suppressed the proteins of iNOS, COX2, TNF-α, IL-6 expression. Furthermore, nCGA also inhibited NF-κB activation and blocked MAPKs signaling pathway phosphorylation. In addition, we found nCGA significantly increased the expression of HO-1 via activating the AMPK/Nrf2 signaling pathway to attenuate the inflammatory response, whereas this protective effect of nCGA was reversed by pre-treatment with compound C (C.C, an AMPK inhibitor). Therefore, all these results indicated that nCGA might act as a natural anti-inflammatory agent for the treatment of acute pneumonia.

Molecular Characterization and Source Identification of Atmospheric Particulate Organosulfates Using Ultrahigh Resolution Mass Spectrometry.

Organosulfates (OSs) have been observed as substantial constituents of atmospheric organic aerosol (OA) in a wide range of environments; however, the chemical composition, sources, and formation mechanism of OSs are still not well understood. In this study, we first created an "OS precursor map" based on the elemental composition of previous OS chamber experiments. Then, according to this "OS precursor map", we estimated the possible sources and molecular structures of OSs in atmospheric PM2.5 (particles with aerodynamic diameter ≤ 2.5 µm) samples, which were collected in urban areas of Beijing (China) and Mainz (Germany) and analyzed by ultrahigh-performance liquid chromatography (UHPLC) coupled with an Orbitrap mass spectrometer. On the basis of the "OS precursor map", together with the polarity information provided by UHPLC, OSs in Mainz samples are suggested to be mainly derived from isoprene/glyoxal or other unknown small polar organic compounds, while OSs in Beijing samples were generated from both isoprene/glyoxal and anthropogenic sources (e.g., long-chain alkanes and aromatics). The nitrooxy-OSs in the clean aerosol samples were mainly derived from monoterpenes, while much fewer monoterpene-derived nitrooxy-OSs were obtained in the polluted aerosol samples, showing that nitrooxy-OS formation is affected by different precursors in clean and polluted air conditions.

Deep transfer learning for source ranging: Deep-sea experiment results.

A deep transfer learning for underwater source ranging is proposed, which migrates the predictive ability obtained from synthetic environment (source domain) into an experimental sea area (target domain). A deep neural network is first trained on large synthetic datasets generated from historical environmental data, and then part of the neural network is refined on collected data set for source ranging. Its performance is tested on a deep-sea experiment through comparing with convolutional neural networks of different training datasets. Data processing results demonstrate that the ranging accuracy is considerably improved by the proposed method, which can be easily adapted for related areas.

Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Residential Coal Combustion.

Residential coal combustion is a significant contributor to particulate urban air pollution in Chinese mega cities and some regions in Europe. While the particulate emission factors and the chemical characteristics of the organic and inorganic aerosol from coal combustion have been extensively studied, the chemical composition and nonmethane organic gas (NMOG) emission factors from residential coal combustion are mostly unknown. We conducted 23 individual burns in a traditional Chinese stove used for heating and cooking using five different coals with Chinese origins, characterizing the NMOG emissions using a proton transfer reaction time-of-flight mass spectrometer. The measured emission factors range from 1.5 to 14.1 g/kgcoal for bituminous coals and are below 0.1 g/kgcoal for anthracite coals. The emission factors from the bituminous coals are mostly influenced by the time until the coal is fully ignited. The emissions from the bituminous coals are dominated by aromatic and oxygenated aromatic compounds with a significant contribution of hydrocarbons. The results of this study can help to improve urban air pollution modeling in China and Eastern Europe and can be used to constrain a coal burning factor in ambient gas phase positive matrix factorization studies.

Brown Carbon Aerosol in Urban Xi'an, Northwest China: The Composition and Light Absorption Properties.

Light-absorbing organic carbon (i.e., brown carbon or BrC) in the atmospheric aerosol has significant contribution to light absorption and radiative forcing. However, the link between BrC optical properties and chemical composition remains poorly constrained. In this study, we combine spectrophotometric measurements and chemical analyses of BrC samples collected from July 2008 to June 2009 in urban Xi'an, Northwest China. Elevated BrC was observed in winter (5 times higher than in summer), largely due to increased emissions from wintertime domestic biomass burning. The light absorption coefficient of methanol-soluble BrC at 365 nm (on average approximately twice that of water-soluble BrC) was found to correlate strongly with both parent polycyclic aromatic hydrocarbons (parent-PAHs, 27 species) and their carbonyl oxygenated derivatives (carbonyl-OPAHs, 15 species) in all seasons ( r2 > 0.61). These measured parent-PAHs and carbonyl-OPAHs account for on average ∼1.7% of the overall absorption of methanol-soluble BrC, about 5 times higher than their mass fraction in total organic carbon (OC, ∼0.35%). The fractional solar absorption by BrC relative to element carbon (EC) in the ultraviolet range (300-400 nm) is significant during winter (42 ± 18% for water-soluble BrC and 76 ± 29% for methanol-soluble BrC), which may greatly affect the radiative balance and tropospheric photochemistry and therefore the climate and air quality.

Biodegradation of Pendimethalin by Paracoccus sp. P13.

In this study, a bacterial strain P13 capable of degrading pendimethalin was isolated from the soil of a fruit garden. Based on observed cellular morphology and physiology characteristics and a phylogenetic analysis of 16S rRNA gene sequences, strain P13 was identified as a member of the genus Paracoccus. Strain P13 grew on pendimethalin as the sole carbon source, and could degrade 100 mg/L pendimethalin within 2 days and 200 mg/L pendimethalin within 5 days. Pendimethalin degradation was proposed to be initiated by oxidation ring cleavage to yield 1,3-dinitro-2-(pentan-3-ylamino)butane-1,4-diol, an alkane organic compound that was identified by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), which then underwent a series of enzymatic reactions to produce CO2 and H2O. The optimal pH and temperature for pendimethalin degradation by strain P13 were 7.0 and 30 °C, respectively. This study identified the bacterial strain Paracoccus sp. P13, which degraded pendimethalin with a relatively high efficiency, and presents a previously unreported microbial pendimethalin degradation pathway.

Pendimethalin Nitroreductase Is Responsible for the Initial Pendimethalin Degradation Step in Bacillus subtilis Y3.

Pendimethalin [N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine] is a selective preemergence dinitroaniline herbicide. Several fungi and bacteria have been reported to degrade pendimethalin, but the enzymes or genes involved in this process have not been characterized. Nitroreduction is the initial degradation and detoxification step for pendimethalin. In this study, a pendimethalin nitroreductase (PNR), responsible for the nitroreduction of pendimethalin, was purified from the pendimethalin-degrading strain Bacillus subtilis Y3. Based on a comparison of its mass fingerprints with all of the deduced proteins from the draft genome of strain Y3, a protein annotated as a nitroreductase was identified, and its corresponding encoding gene was termed pnr PNR was a functional homodimer with a subunit molecular mass of approximately 23 kDa. PNR reduced the C-6 nitro group of the aromatic ring of pendimethalin, yielding 2-nitro-6-amino-N-(1-ethylpropyl)-3,4-xylidine. PNR could also catalyze the nitroreduction of three other major varieties of dinitroaniline herbicides, including butralin, oryzalin, and trifluralin. However, the number of reduced nitro groups was two instead of one, which differed from the nitroreduction of pendimethalin by PNR and which may be due to the symmetry in the chemical structures of the two nitro groups. A detoxification assay revealed that 2-nitro-6-amino-N-(1-ethylpropyl)-3,4-xylidine (PNR-reduced pendimethalin) showed no inhibitory effect on the growth of Saccharomyces cerevisiae BY4741, whereas pendimethalin showed an obvious inhibitory effect on its growth, indicating the detoxification effect of pendimethalin by PNR. Therefore, PNR has potential in pendimethalin detoxification applications. This report describes an enzyme (and corresponding gene) involved in the biodegradation of pendimethalin and dinitroaniline herbicides. IMPORTANCE: Pendimethalin [N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine] is a widely used selective preemergence dinitroaniline herbicide, and its residue has been frequently detected in the environment. The U.S. Environmental Protection Agency (EPA) has classified pendimethalin as a persistent bioaccumulative toxin. To date, no enzymes or genes involved in pendimethalin biodegradation have been reported. In the present study, the gene pnr, which encodes the nitroreductase PNR, responsible for the nitroreduction of pendimethalin, was cloned from the pendimethalin-degrading strain Bacillus subtilis Y3. PNR could also catalyze the nitroreduction of three other major varieties of dinitroaniline herbicides, including butralin, oryzalin, and trifluralin. The reduction of pendimethalin by PNR might eliminate its toxicity against Saccharomyces cerevisiae BY4741, indicating the application potential of PNR in the detoxification of pendimethalin.

A novel amidohydrolase (DmhA) from Sphingomonas sp. that can hydrolyze the organophosphorus pesticide dimethoate to dimethoate carboxylic acid and methylamine.

OBJECTIVES: To characterize a novel dimethoate amidohydrolase from Sphingomonas sp. DC-6. RESULTS: A gene, dmhA, encoding the dimethoate amidohydrolase responsible for transforming dimethoate to dimethoate carboxylic acid and methylamine, was cloned from Sphingomonas sp. DC-6. Sequence analysis and molecular modeling indicate that DmhA shares 31-57 % amino acid sequence identities with other functionally confirmed amidohydrolase. DmhA was expressed in Escherichia coli BL21 (DE3) and purified by Ni-NTA affinity chromatography. The purified DmhA could hydrolyze 4-acetaminophenol, dimethoate and propanil. DmhA activity was optimal at 30 °C and pH 7.5. Hg(2+), Zn(2+), Cu(2+), Cd(2+), Tween 80, Triton X-100 or SDS strongly inhibited its activity. The K m and k cat values of DmhA for dimethoate are 0.02 mM and 1.2 s(-1), respectively. CONCLUSIONS: DmhA was confirmed to be a novel dimethoate amidohydrolase which could eliminate the toxicity of dimethoate, providing a novel gene resource for the development of pesticide-degrading enzyme preparation and mechanistic study of dimethoate hydrolysis.

Biodegradation of pendimethalin by Bacillus subtilis Y3.

A bacterium strain Y3, capable of efficiently degrading pendimethalin, was isolated from activated sludge and identified as Bacillus subtilis according to its phenotypic features and 16S rRNA phylogenetic analysis. This strain could grow on pendimethalin as a sole carbon source and degrade 99.5% of 100mg/L pendimethalin within 2.5days in batch liquid culture, demonstrating a greater efficiency than any other reported strains. Three metabolic products, 6-aminopendimethalin, 5-amino-2-methyl-3-nitroso-4-(pentan-3-ylamino) benzoic acid, and 8-amino-2-ethyl-5-(hydroxymethyl)-1,2-dihydroquinoxaline-6-carboxylic acid, were identified by HPLC-MS/MS, and a new microbial degradation pathway was proposed. A nitroreductase catalyzing nitroreduction of pendimethalin to 6-aminopendimethalin was detected in the cell lysate of strain Y3. The cofactor was nicotinamide adenine dinucleotide phosphate (NADPH) or more preferably nicotinamide adenine dinucleotide (NADH). The optimal temperature and pH for the nitroreductase were 30°C and 7.5, respectively. Hg(2+), Ni(2+), Pb(2+), Co(2+), Mn(2+) Cu(2+), Ag(+), and EDTA severely inhibited the nitroreductase activity, whereas Fe(2+), Mg(2+), and Ca(2+) enhanced it. This study provides an efficient pendimethalin-degrading microorganism and broadens the knowledge of the microbial degradation pathway of pendimethalin.

Nitratireductor soli sp. nov., isolated from phenol-contaminated soil.

Strain ZZ-1(T), a Gram-negative, rod-shaped bacterium, motile by flagella, was isolated from phenol-contaminated soil. Strain ZZ-1(T) was found to grow at 15-37 °C (optimum 25-30 °C), at pH 6.0-10.0 (optimum pH 7.5) and with 0-8.0% (w/v) NaCl (optimum 0.5%). The isolate was found to be able to reduce nitrate to nitrite, but not to nitrogen. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain ZZ-1(T) is a member of the genus Nitratireductor, and shows high sequence similarities to Nitratireductor pacificus MCCC 1A01024(T) (98.5%) and lower (<97%) sequence similarities to all other Nitratireductor species. Chemotaxonomic analysis revealed that strain ZZ-1(T) possesses Q-10 as the predominant ubiquinone and Summed feature 8(C(18:1) ω6c and/or C(18:1) ω7c; 66.6%), C(19:0) ω8c cyclo (23.3%), C(18:0) (3.4%), iso-C(17:0) (2.3%) and C(17:0) (1.0%) as the major fatty acids. The polar lipids of strain ZZ-1(T) were determined to be diphosphatidylglycerol, phosphatidylcholine, phospholipids, aminolipids, a glycolipid and an aminophospholipid. The DNA G+C content was determined to be 64.1 mol%. Based on the draft genome sequence, the DNA-DNA hybridization estimate value between strain ZZ-1(T) and N. pacificus MCCC 1A01024(T) was 46.5 ± 3.0% and ANI was 75.9 %. The combination of phylogenetic analysis, phenotypic characteristics, chemotaxonomic data and DNA-DNA hybridization supports the conclusion that strain ZZ-1(T) represents a novel species of the genus Nitratireductor, for which the name Nitratireductor soli sp. nov. is proposed. The type strain is ZZ-1(T) (=JCM 30640(T) = MCCC 1K00508(T)).