Reduction of selenite and tellurite by a highly metal-tolerant marine bacterium.

Selenium (Se) and tellurium (Te) contaminations in soils and water bodies have been widely reported in recent years. Se(IV) and Te(IV) were regarded as their most dangerous forms. Microbial treatments of Se(IV)- and Te(IV)-containing wastes are promising approaches because of their environmentally friendly and sustainable advantages. However, the salt-tolerant microbial resources that can be used for selenium/tellurium pollution control are still limited since industrial wastewaters usually contain a large number of salts. In this study, a marine Shewanella sp. FDA-1 (FDA-1) was reported for efficient Se(IV) and Te(IV) reduction under saline conditions. Process and product analyses were performed to investigate the bioreduction processes of Se(IV) and Te(IV). The results showed that FDA-1 can effectively reduce Se(IV) and Te(IV) to Se0 and Te0 Se(IV)/Te(IV) to Se0/Te0 in 72 h, which were further confirmed by XRD and XPS analyses. In addition, enzymatic and RT‒qPCR assays showed that flavin-related proteins, reductases, dehydrogenases, etc., could be involved in the bioreduction of Se(IV)/Te(IV). Overall, our results demonstrate the ability of FDA-1 to reduce high concentrations of Se(IV)/or Te(IV) to Se0/or Te0 under saline conditions and thus provide efficient microbial candidate for controlling Se and Te pollution.

Effects of suspended particles and dispersants on marine oil snow formation of crude oil/diesel oil.

Marine oil snow (MOS) potentially forms after an oil spill. To fully understand the mechanism of its formation, we investigated the effects of suspended particles (SP) and dispersants on MOS formation of crude oil and diesel oil by laboratory experiments. In the crude oil experiment, the SP concentration of 0.2 g L-1 was more suitable for crude oil MOS formation. The addition of dispersants significantly stimulated N and TV during MS/MOS formation of SP at 0.4 g L-1 and 0.8 g L-1 concentration (p < 0.05). Without SP, the dispersants also stimulated crude oil MOS formation. Furthermore, the concentration of SP had a significantly positive effect on the reduction of the total amount of N-alkanes (p < 0.05). In the diesel oil experiment, after adding dispersants to diesel oil, the maximum N, Dm, and TV values at a SP concentration of 0.2 g L-1 were significantly higher than those at 0.4 g L-1 and 0.8 g L-1 (p < 0.05). Besides, we found that dispersants stimulated MOS formation in diesel oil at a SP concentration of 0.2 g L-1. However, the dispersants had an inhibitory effect on diesel oil MOS formation without SP. Notably, the MOS formed by diesel oil appeared white, unlike the black MOS associated with crude oil. These findings are important for the environmental impact of oil spills and elevated SP concentrations.

How iron-bearing minerals affect the biological reduction of Sb(V): A newly discovered function of nitrate reductase.

As a toxic element of global concern, the elevated concentration of antimony (Sb) in the environment has attracted increasing attention. Microorganisms have been reported as important driving forces for Sb transformation. Iron (Fe) is the most important metal associated element of Sb, however, how Fe-bearing minerals affect the biological transformation of Sb is still unclear. In this study, the effects of Fe-bearing minerals on biological Sb(V) reduction were investigated by employing a marine Shewanella sp. CNZ-1 (CNZ-1). Our results showed that the presence of hematite, magnetite and ferrihydrite (1 g/L) resulted in a decrease in Sb(III) concentration of ~19-31 % compared to the Fe(III)-minerals free system. The calculated Sb(V) reduction rates are 0.0256 (R2 0.71), 0.0389 (R2 0.87), 0.0299 (R2 0.96) and 0.0428 (R2 0.95) h-1 in the hematite-, magnetite-, ferrihydrite-supplemented and Fe(III)-minerals free systems, respectively. The cube-shaped Sb2O3 was characterized as a reductive product by using XRD, XPS, FTIR, TG and SEM approaches. Differential proteomic analysis showed that flagellar protein, cytochrome c, electron transfer flavoprotein, nitrate reductase and polysulfide reductase (up-regulation >1.5-fold, p value <0.05) were supposed to be included in the electron transport pathway of Sb(V) reduction by strain CNZ-1, and the key role of nitrate reductases was further highlighted during this reaction process based on the RT-qPCR and confirmatory experiments. Overall, these findings are beneficial to understand the environmental fate of Sb in the presence of Fe-bearing minerals and provide guidance in developing the bacteria/enzyme-mediated control strategy for Sb pollution.

Porphyra haitanensis Polysaccharides Attenuates Blood Lipid via Gut-Liver Axis in Diet-Induced High-Fat Mesocricetus auratus through Multiple Integrated Omics.

SCOPE: Hyperlipidemia is currently a global public health problem severely affecting people's physical and mental health, as well as their quality of life. METHODS AND RESULTS: The present study is aimed at revealing the mechanism of Porphyra haitanensis polysaccharide (PHP) in decreasing blood lipids by acting through gut-liver axis in Mesocricetus auratus fed a high-fat diet. PHP significantly prevented increases in serum total cholesterol, triglycerides and low-density lipoprotein cholesterol, and alleviated damage to liver cells induced by a high-fat diet M. auratus, in a dose-dependent manner. PHP promotes proliferation of Muribaculaceae and Faecalibaculum, thereby enhancing the production of butyric acid both in the colon and liver, particularly high-dose PHP (HPHP). Low-dose PHP (LPHP) promotes the expression of phosphatidylcholine metabolites and fatty acid transport genes, and inhibits the expression of genes involved in fat degradation (Abhd5), adipogenesis (Me1), fatty acid synthesis (Fasn and Pnpla3), and fatty acid chain elongation (Elovl6) in the liver. However, HPHP inhibits the expression of triglyceride metabolites and promotes the expression of fatty acid transporter (CD36), fatty acid oxidation (Acacb), and peroxisome proliferator-activated receptor gamma (PPARg) genes in the liver. CONCLUSION: PHP regulates lipid metabolism through the gut microbiota, and the gut-liver axis plays an important role in its hypolipidemic effects.

Application of X-ray diffraction and energy dispersive spectroscopy in the isolation of sulfated polysaccharide from Porphyra haitanensis and its antioxidant capacity under in vitro digestion.

BACKGROUND: The separation and purification of Porphyra haitanensis polysaccharide (PHP), and the determination of changes in molecular weight (Mw) and antioxidant capacity after in vitro digestion, were undertaken. RESULTS: Analysis of two polysaccharide fractions (PHP0.5-1-UF and PHP1.0-1-UF) by various techniques showed that they were very pure sulfated polysaccharides without pigment or protein. PHP0.5-1-UF was filamentous or 'tape-like' sheets, whereas PHP1.0-1-UF had some filaments and large numbers of rounded aggregates. The Mw of PHP, PHP0.5-1-UF and PHP1.0-1-UF was 2.06 × 106 (±2.02%), 6.68 × 106 (±3.17%), and 1.14 × 106 (±3.44%) (g mol-1 ), respectively. After in vitro digestion, the Mw of PHP, PHP0.5-1-UF, and PHP1.0-1-UF decreased. Their antioxidant capacities were markedly higher than before digestion, especially PHP0.5-1-UF and its digestion products, which might be related to the reductions in Mw. CONCLUSION: These findings provide a greater understanding of the separation and purification of sulfated polysaccharides and the influence of digestion on biological activity. They also contribute to the practical application of sulfated polysaccharides in functional foods. © 2021 Society of Chemical Industry.

Nutrient depletion is the main limiting factor in the crude oil bioaugmentation process.

The biodegradation was considered as the prime mechanism of crude oil degradation. To validate the efficacy and survival of the crude oil-degrading strain in a bioremediation process, the enhanced green fluorescent protein gene (egfp) was introduced into Acinetobacter sp. HC8-3S. In this study, an oil-contaminated sediment microcosm was conducted to investigate the temporal dynamics of the physicochemical characterization and microbial community in response to bacterium amendment. The introduced strains were able to survive, flourish and degrade crude oil quickly in the early stage of the bioremediation. However, the high abundance cannot be maintained due to the ammonium (NH4+-N) and phosphorus (PO43--P) contents decreased rapidly after 15 days of remediation. The sediment microbial community changed considerably and reached relatively stable after nutrient depletion. Therefore, the addition of crude oil and degrading cells did not show a long-time impact on the original microbial communities, and sufficient nitrogen and phosphorus nutrients ensures the survive and activity of degrader. Our studies expand the understanding of the crude oil degradative processes, which will help to develop more rational bioremediation strategies.

Ni(II) and Cu(II) removal from aqueous solution by a heavy metal-resistance bacterium: kinetic, isotherm and mechanism studies.

The potentiality of a heavy metal-resistance bacterium Acinetobacter sp. HK-1 for removing Ni(II) and Cu(II) ions from aqueous solution and the biosorption mechanism were investigated in this study. The effects of pH, contact time and Ni(II)/Cu(II) concentration on the adsorption process were evaluated and the maximum biosorption capacity of strain HK-1 was found to be 56.65 mg/g for Ni(II) and 157.2 mg/g for Cu(II), respectively. The experimental kinetic data fit well with the pseudo-second-order model (R2 > 0.98) and the biosorption process was best explained by the Langmuir-Freundlich dual model (R2 > 0.97). The morphologies of HK-1 before and after adsorption in a Ni(II)/Cu(II) supplemented system were compared using a scanning electron microscope. After adsorption, the valence state of Ni(II)/Cu(II) was not changed and the formation of nickel/copper phosphate was observed using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The results of Fourier transform infrared spectroscopy and XPS further indicated that amine, phosphate and carboxyl groups were involved in the biosorption process. Cu(II) biosorption by Acinetobacter sp. was firstly reported. Based on the above results, it can be concluded that Acinetobacter sp. HK-1 has a promising application in Ni(II) and Cu(II) ion removal from industrial wastewater.

Distributions and sources of petroleum, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Bohai Bay and its adjacent river, China.

Surface sediment samples from Bohai Bay and its adjacent river, China, were analyzed for aliphatic hydrocarbon, PAHs and biomarkers in order to determine the distribution, composition and source of organic matter in a coastal environment. Results suggested that the input of organic matter from anthropogenic activities has a more significant influence on its distribution than that from natural processes. Petroleum contamination, mainly from offshore oil exploration and discharge of pollutants from rivers, was the main source of n-alkanes. PAHs were mostly of pyrogenic origin; while some sites in Yellow River Estuary were derived mainly from the petrogenic sources. The toxic assessment suggested that the PAHs in surface sediments will not cause immediately adverse biological effects in sediments from Bohai Bay and its adjacent river, China.

[Induction of CuZn-SOD mRNA expression and activity by PGMS in rat liver].

AIM: To study the effect of propylene glycol mannate sulfate (PGMS) on induction of CuZn-SOD. METHODS: Wistar rats were given PGMS p.o. at different doses (0, 18.9, 37.8 and 75.6 mg.kg-1.d) for ten days. Then the rats were sacrificed and the total RNA was extracted from the livers. The total RNA samples were loaded on a 1% agarose gel to detect the quality of total RNA. RT-PCR was applied to study the expression of CuZn-SOD mRNA in rat livers. The amplified products were detected by the 1.5% agarose gel electrophoresis. Simultaneously, the CuZn-SOD activities in rat liver were determined by nitrite method. RESULTS: The total RNA extracted from rat livers was integrated without being decomposed by RNase. The level of CuZn-SOD mRNA of the high-dosage group (75.6 mg.kg-1.d) was higher than that of the control group (0 mg.kg-1.d) (P < 0.01); the CuZn-SOD activities of the high-dosage group were significantly higher than those of the control group (P < 0.001) and the CuZn-SOD activities of the middle- (37.8 mg.kg-1.d) and low-dosage groups (18.9 mg.kg-1.d) were higher than those of the control group (P < 0.01). CONCLUSION: PGMS can increase the CuZn-SOD activities as well as CuZn-SOD on mRNA level. Therefore, it is possible for PGMS to counteract Atherosclerosis (AS) by inducing the expression of CuZn-SOD.