Assessment of source-oriented health risk associated with the oral ingestion of heavy metals in dust within an iron/steel smelting-affected area of the North China Plain.

Heavy metals (HMs) from iron/steel smelting activities pose notable risks to human health, especially to those living around industrial facilities of North China Plain, the base of China's steel production. In this study, 78 outdoor windowsill dust samples were collected around a large-scale iron/steel smelter with more than 65 years of production history in the western North China Plain. Nine HMs were analysed to comprehensively assess the health risks by integrating Monte Carlo simulation, oral bioaccessibility, and source apportionment. Results showed serious pollution with Cd, Pb, and Zn based on their geo-accumulation index values and concentrations. Four potential sources including industrial sources (49.85%), traffic sources (21.78%), natural sources (20.58%), and coal combustion (7.79%) were quantitatively identified by multivariate statistical analysis. The oral bioaccessibilities of HMs determined by the physiologically based extraction test ranged from 0.02% to 65.16%. Zn, Mn, Cd, and Pb had higher bioaccessibilities than other HMs. After incorporating oral bioavailability adjustments, noncarcinogenic and carcinogenic risks were significantly reduced, especially for adults. The mean hazard index (HI) for children and adults was below the safety threshold (1.0), whereas the mean of the total carcinogenic risk (TCR) based on HM bioaccessibilities in the gastric phase remained above the acceptable level (1.0E-06) (children: 5.20E-06; adults: 1.16E-06). Traffic sources warranted increased concern as it substantially increased TCR. Cd was identified as the priority pollution in iron/steel smelting areas. Assessing source-oriented health risks associated with oral ingestion exposure can guide the management and control of HM contamination within iron/steel smelting-affected areas.

Ion Mobility-Derived Collision Cross-Sections Add Extra Capability in Distinguishing Isomers and Compounds with Similar Retention Times: The Case of Aphidicolanes.

The hyphenation of ion mobility spectrometry with high-resolution mass spectrometry has been widely used in the characterization of various metabolites. Nevertheless, such a powerful tool remains largely unexplored in natural products research, possibly mainly due to the lack of available compounds. To evaluate the ability of collision cross-sections (CCSs) in characterizing compounds, especially isomeric natural products, here we measured and compared the traveling-wave IMS-derived nitrogen CCS values for 75 marine-derived aphidicolanes. We established a CCS database for these compounds which contained 227 CCS values of different adducts. When comparing the CCS differences, 36 of 57 pairs (over 60%) of chromatographically neighboring compounds showed a ΔCCS over 2%. What is more, 64 of 104 isomeric pairs (over 60%) of aphidicolanes can be distinguished by their CCS values, and 13 of 18 pairs (over 70%) of chromatographically indistinguishable isomers can be differentiated from the mobility dimension. Our results strongly supported CCS as an important parameter with good orthogonality and complementarity with retention time. CCS is expected to play an important role in distinguishing complex and diverse marine natural products.

A rapid and efficient method for the extraction and identification of menaquinones from Actinomycetes in wet biomass.

BACKGROUND: Menaquinones are constituents of prokaryote cell membranes where they play important functions during electron transport. Menaquinone profiles are strongly recommended for species classification when proposing a new Actinomycetes taxon. Presently, the most widely used methods to determine menaquinones are based on freeze-dried cells. Taxonomic research in our lab has revealed that menaquinone concentrations are low for some species of the genus Microbacterium, leading to difficulties in identifying menaquinones. RESULTS: Menaquinones extracted using the novel lysozyme-chloroform-methanol (LCM) method were comparable in quality to those obtained using the Collins method, the most widely used method. All tested strains extracted via the LCM method showed higher concentrations of menaquinones than those extracted via the Collins method. For some Microbacterium strains, the LCM method exhibited higher sensitivity than the Collins method, and more trace menaquinones were detected with the LCM method than the Collins method. In addition, LCM method is faster than the Collins method because it uses wet cells. CONCLUSION: The LCM method is a simple, rapid and efficient technique for the extraction and identification of menaquinones from Actinomycetes.

Knockout of a PLD gene in Schizochytrium limacinum SR21 enhances docosahexaenoic acid accumulation by modulation of the phospholipid profile.

BACKGROUND: The hydrolysis and transphosphatidylation of phospholipase D (PLD) play important roles in the interconversion of phospholipids (PLs), which has been shown to profoundly impact lipid metabolism in plants. In this study, the effect of the PLD1 gene of Schizochytrium limacinum SR21 (S. limacinum SR21) on lipid metabolism was investigated. RESULTS: PLD1 knockout had little impact on cell growth and lipid production, but it significantly improved the percentage of polyunsaturated fatty acids in lipids, of which docosahexaenoic acid (DHA) content increased by 13.3% compared to the wild-type strain. Phospholipomics and real-time quantitative PCR analysis revealed the knockout of PLD1 reduced the interexchange and increased de novo synthesis of PLs, which altered the composition of PLs, accompanied by a final decrease in phosphatidylcholine (PC) and an increase in phosphatidylinositol, lysophosphatidylcholine, and phosphatidic acid levels. PLD1 knockout also increased DHA content in triglycerides (TAGs) and decreased it in PLs. CONCLUSIONS: These results indicate that PLD1 mainly performs the transphosphatidylation activity in S. limacinum SR21, and its knockout promotes the migration of DHA from PLs to TAGs, which is conducive to DHA accumulation and storage in TAGs via an acyl CoA-independent pathway. This study provides a novel approach for identifying the mechanism of DHA accumulation and metabolic regulation strategies for DHA production in S. limacinum SR21.

Multiproxy probing of anthropogenic influences on the different components of dissolved organic matter in coastal rainwater.

In an environment that is tightly linked to humankind, how anthropogenic activity affects the quality and quantity of dissolved organic matter (DOM) in atmospheric depositions is not well understood. In this study, dissolved organic carbon (DOC), UV-vis spectra combined with molecular markers, including formic acid (FA), acetic acid (AA) and dissolved black carbon (DBC), were applied to track the temporal variation and influential factors of rainwater DOM at a coastal site. The ranges of DOC, light absorption at 254 nm (a254), FA, AA and DBC were 23.2-471 µmol L-1, 0.16-10.6 m-1, 0.12-23.5 µmol L-1, 0.44-37.8 µmol L-1 and 0.02-4.8 µmol L-1, respectively. The negative correlations between DOC, a254, AA and precipitation amount revealed a dilution effect. The concentrations of all measured DOM components were statistically different among different seasons with the highest value in spring. Higher DOM concentrations also occurred in the rain with backward trajectories influenced by the land. Compared to the nearby riverine DOM, the DOC-specific UV absorbance (SUVA254) of rainwater was lower, suggesting lower aromaticity of rainwater DOM. Significant correlations among different DOM components suggest that they shared similar sources or were affected by the same processes, while the significant correlations with anions (SO42-, F- and NO3-) and the ratio of FA to AA all suggested that the direct emission and secondary production from anthropogenic emissions (fossil fuel burning, biomass and biofuel burning) played important roles in regulating the level of DOM concentration in rainwater. Correlations with environmental variables (PM2.5, CO and NO2) further confirmed the input from anthropogenic activities. Furthermore, the monthly wet atmospheric deposition fluxes of DOM components (except DBC) can be successfully simulated by monthly precipitation and monthly average values of PM2.5 and NO2. Future studies should examine how atmospheric deposition affects the biogeochemical cycles in coastal regions.

The genome of a hadal sea cucumber reveals novel adaptive strategies to deep-sea environments.

How organisms cope with coldness and high pressure in the hadal zone remains poorly understood. Here, we sequenced and assembled the genome of hadal sea cucumber Paelopatides sp. Yap with high quality and explored its potential mechanisms for deep-sea adaptation. First, the expansion of ACOX1 for rate-limiting enzyme in the DHA synthesis pathway, increased DHA content in the phospholipid bilayer, and positive selection of EPT1 may maintain cell membrane fluidity. Second, three genes for translation initiation factors and two for ribosomal proteins underwent expansion, and three ribosomal protein genes were positively selected, which may ameliorate the protein synthesis inhibition or ribosome dissociation in the hadal zone. Third, expansion and positive selection of genes associated with stalled replication fork recovery and DNA repair suggest improvements in DNA protection. This is the first genome sequence of a hadal invertebrate. Our results provide insights into the genetic adaptations used by invertebrate in deep oceans.

Description of Microbacterium luteum sp. nov., Microbacterium cremeum sp. nov., and Microbacterium atlanticum sp. nov., three novel C50 carotenoid producing bacteria.

We have identified three Microbacterium strains, A18JL200T, NY27T, and WY121T, that produce C50 carotenoids. Taxonomy shows they represent three novel species. These strains shared < 98.5% 16S rRNA gene sequence identity with each other and were closely related to Microbacterium aquimaris JCM 15625T, Microbacterium yannicii JCM 18959T, Microbacterium ureisolvens CFH S00084T, and Microbacterium hibisci CCTCC AB 2016180T. Digital DNA-DNA hybridization (dDDH) values and average nucleotide identity (ANI) showed differences among the three strains and from their closest relatives, with values ranging from 20.4% to 34.6% and 75.5% to 87.6%, respectively. These values are below the threshold for species discrimination. Both morphology and physiology also differed from those of phylogenetically related Microbacterium species, supporting that they are indeed novel species. These strains produce C50 carotenoids (mainly decaprenoxanthin). Among the three novel species, A18JL200T had the highest total yield in carotenoids (6.1 mg/L or 1.2 mg/g dry cell weight). Unusual dual isoprenoid biosynthetic pathways (methylerythritol phosphate and mevalonate pathways) were annotated for strain A18JL200T. In summary, we found strains of the genus Microbacterium that are potential producers of C50 carotenoids, but their genome has to be investigated further.