High Salt Environment Research Articles

Transcriptomic Profiling Provides Molecular Insights Into Hydrogen Peroxide-Enhanced Arabidopsis Growth and Its Salt Tolerance.

Salt stress is an important environmental factor limiting plant growth and crop production. Plant adaptation to salt stress can be improved by chemical pretreatment. This study aims to identify whether hydrogen peroxide (H2O2) pretreatment of seedlings affects the stress tolerance of Arabidopsis thaliana seedlings. The results show that pretreatment with H2O2 at appropriate concentrations enhances the salt tolerance ability of Arabidopsis seedlings, as revealed by lower Na+ levels, greater K+ levels, and improved K+/Na+ ratios in leaves. Furthermore, H2O2 pretreatment improves the membrane properties by reducing the relative membrane permeability (RMP) and malonaldehyde (MDA) content in addition to improving the activities of antioxidant enzymes, including superoxide dismutase, and glutathione peroxidase. Our transcription data show that exogenous H2O2 pretreatment leads to the induced expression of cell cycle, redox regulation, and cell wall organization-related genes in Arabidopsis, which may accelerate cell proliferation, enhance tolerance to osmotic stress, maintain the redox balance, and remodel the cell walls of plants in subsequent high-salt environments.

Carbon nanotube enhanced water-based drilling fluid for high temperature and high salinity deep resource development

Drilling fluids face failure during drilling deep reservoir with high temperature and high salt. The experimental results show that high temperature and salinity reduce the negative charge on the surface of bentonite in the drilling fluid and cause the coalescence of bentonite particles. As a result, the particles coalesce, the grid structure is destroyed, and the rheological properties, rock-carrying capacity and filtration properties are lost. To resolve the foregoing, in this study, 0.05-wt% carbon nanotubes are introduced into a 4% bentonite drilling fluid under conditions where the temperature and concentration of added NaCl reach 180 °C and 10 wt%, respectively. The carbon nanotubes adsorb on the bentonite surface and increase the space among bentonite particles. The steric hindrance prevents the coalescence of bentonite in high temperature and high salt environment. Thus bentonite maintains the small size distribution of bentonite and supports the bentonite grid structure in the drilling fluid. As a result, the rock-carrying capacity of the drilling fluid increases by 85.1%. Moreover, the mud cake formed by the accumulation of small-sized bentonite particles is dense; consequently, the filtration of bentonite drilling fluid reduced by 30.2%.

Safety and the probiotic potential of Bifidobacterium animalis CP-9.

Bifidobacterium animalis CP-9 was a commensal strain isolated from human breast milk. In this study, genetic and 90-day oral toxicity were assessed in rodents for its safety. Ames test as well as in vivo bone marrow micronucleus and spermatocyte chromosomal aberration were surveyed in mice. B. animalis CP-9 exhibited no mutagenic activity in the Ames test at the highest tested dosage (5000µg/plate) with or without metabolic activation. No evidence of in vivo genetic toxicity was observed at the maximum tested dosage of 10g/kg body weight (BW). Furthermore, there was no statistically significant difference of the biochemical and histological parameters in the rats administrated with B. animalis CP-9 at dosages of 0, 0.25, 0.5, or 1.5g/kg BW/day. No indication of concern for pathogenicity was exhibited during evaluation of Bifidobacterium ssp. generally, or B. animalis specifically. It was noted that B. animalis CP-9 was able to survive in gastric acid-like and high bile salt environment, and showed strong adhesion to the intestinal epithelial cells, Caco-2. Intriguingly, B. animalis CP-9 decreased olic acid-induced triglyceral (TG) accumulation in the Caco-2 cells, and viable B. animalis CP-9 had a better bacteriostatic activity compared to another well-documented B. animalis ssp. lactis, BB-12. Based on the present study, B. animalis CP-9 can be a safe probiotic supplement and may improve the health of host. PRACTICAL APPLICATION: Although the health benefits of probiotics are well known, the safety of a probiotic product is acquired particularly for a long-term consumption. We conduct the safety of B. animalis CP-9 isolated from human breast milk, and demonstrate no toxicity concern in vitro and in vivo. Hence, B. animalis CP-9 powder can be used as a commercial and safe probiotic supplement with some health benefits.

Structure characterization, antioxidant and emulsifying capacities of exopolysaccharide derived from Tetragenococcus halophilus SNTH-8

Tetragenococcus halophilus exopolysaccharides (THPS) are metabolites released by T. halophilus SNTH-8 to resist a high-salt environment. Although many studies have investigated the mechanisms underlying salt tolerance shown by T. halophilus, structural characteristics as well as antioxidant and emulsifying capacities of THPS remain unclear. In this study, we isolated and purified two components, THPS-1 and THPS-2, from T. halophilus SNTH-8. Purified THPS-1 and THPS-2 were composed of arabinose, xylose, fucose, galactose, glucose, and glucuronic acid at a molar ratio of 1.66:38.95:2.11:26.12:29.73:1.43 and 0.46:40.3:0.54:30.8:1.36:25.54, respectively. The average molecular weights of THPS-1 and THPS-2 were 14.98 kDa and 21.03 kDa, respectively. Moreover, the structures of THPS-1 and THPS-2 were investigated via fourier-transform infrared spectroscopy(FT-IR), nuclear magnetic resonance spectroscopy(NMR), scanning electron microscopy(SEM), and methylation analysis. THPS-1 was a highly branched polysaccharide with a backbone of α-D-(1,4)-Xyl, α-D-(1,6)-Glc and α-D-Xyl as the terminal, while THPS-2 was a highly branched polysaccharide with a backbone of α-D-(1,4)-Xyl and β-D-GlcA as the terminal. The branches were identified as β-D-(1,4,6)-Gal and β-D-(1,6)-Gal. Both THPS-1 and THPS-2 exhibited high antioxidant and emulsifying capacities. Overall, our structural analysis of THPS may further enhance research on natural emulsifiers and antioxidants.

Facile fabrication of multi superlyophobic nano soil coated-mesh surface with excellent corrosion resistance for efficient immiscible liquids separation

A novel strategy for spraying nanosized soil particles on steel mesh to prepare the superlyophobic soil mesh by a facile surface treatment technology, and successfully apply it to various immiscible liquids separation. • A multifunctional, sustainable material for immiscible liquid mixtures separation. • Under nonpolar (polar) liquid superlyophobicity of polar (nonpolar) liquid. • Used chemical properties-structure relationships to give material performance. • Low cost manufacturing, environment friendly, dimplicity of operator. • Good corrosion resistance in acidic, alkaline and high salt environment. Immiscible liquids separation has recently become a worldwide challenge due to the expanding industrial activity. It is still thorny to put forward a universal strategy for constructing multi-superlyophobic surfaces in immiscible liquids systems due to a thermodynamic contradiction. Herein, a low-cost, environmentally friendly pre-wetted nanosized soil coated-mesh (NSCM) was prepared, which shows the property of under-nonpolar-liquid superlyophobic to polar liquid, or under-polar-liquid superlyophobic to nonpolar liquid. The NSCM was fabricated in aqueous solutions by spraying melamine formaldehyde resin modified nanosized soil particles on a stainless-steel mesh for selective immiscible liquid separation. After the NSCM is prewetted with heavy liquid, heavy liquid can be removed from the light immiscible liquid mixtures by gravity. The as-prepared NSCM showed a high separation efficiency of above 99% for a series of immiscible liquids mixtures, even after 60 separation cycles. More importantly, the electrochemical tests indicated that the NSCM exhibited the outstanding durability after being immersed in alkali (pH = 10.0, NaOH), acidic (pH = 4.0, HCl) and high-concentrated salt solutions (3.5 wt% NaCl) for 30 days. The calculated R t values were approximately 1.04 × 10 7 , 2.65 × 10 6 and 7.59 × 10 5 Ω·cm 2 , respectively. And the corresponding corrosion rates were 0.013712, 0.96438, and 2.5818 μm/year, respectively. These excellent performances of the NSCM make it an ideal candidate material for separation, and even in a wider field of sea wastewater treatment.

Novel Polyhydroxybutyrate-Degrading Activity of the Microbulbifer Genus as Confirmed by Microbulbifer sp. SOL03 from the Marine Environment.

Ever since bioplastics were globally introduced to a wide range of industries, the disposal of used products made with bioplastics has become an issue inseparable from their application. Unlike petroleum-based plastics, bioplastics can be completely decomposed into water and carbon dioxide by microorganisms in a relatively short time, which is an advantage. However, there is little information on the specific degraders and accelerating factors for biodegradation. To elucidate a new strain for biodegrading poly-3-hydroxybutyrate (PHB), we screened out one PHB-degrading bacterium, Microbulbifer sp. SOL03, which is the first reported strain from the Microbulbifer genus to show PHB degradation activity, although Microbulbifer species are known to be complex carbohydrate degraders found in high-salt environments. In this study, we evaluated its biodegradability using solid- and liquid-based methods in addition to examining the changes in physical properties throughout the biodegradation process. Furthermore, we established the optimal conditions for biodegradation with respect to temperature, salt concentration, and additional carbon and nitrogen sources; accordingly, a temperature of 37°C with the addition of 3% NaCl without additional carbon sources, was determined to be optimal. In summary, we found that Microbulbifer sp. SOL03 showed a PHB degradation yield of almost 97% after 10 days. To the best of our knowledge, this is the first study to investigate the potent bioplastic degradation activity of Microbulbifer sp., and we believe that it can contribute to the development of bioplastics from application to disposal.

Presence of a Mitovirus Is Associated with Alteration of the Mitochondrial Proteome, as Revealed by Protein-Protein Interaction (PPI) and Co-Expression Network Models in Chenopodium quinoa Plants.

Simple SummaryPlants often harbor persistent plant virus infection transmitted only vertically through seeds, resulting in no obvious symptoms (cryptic infections). Several studies have shown that such cryptic infections provide resilience against abiotic (and biotic) stress. We have recently discovered a new group of cryptic plant viruses infecting mitochondria (plant mitovirus). Mitochondria are cellular organelles displaying a pivotal role in protecting cells from the stress of nature . Here, we look at the proteomic alterations caused by the mitovirus cryptic infection of Chenopodium quinoa by Systems Biology approaches allowing one to evaluate data at holistic level. Quinoa is a domesticated plant species with many exciting features of abiotic stress resistance, and it is distinguished by its exceptional nutritional characteristics, such as the content and quality of proteins, minerals, lipids, and tocopherols. These features determined the growing interest for the quinoa crop by the scientific community and international organizations since they provide opportunities to produce high-value grains in arid, high-salt and high-UV agroecological environments. We discovered that quinoa lines hosting mitovirus activate some metabolic processes that might help them face drought. These findings present a new perspective for breeding crop plants through the augmented genome provided by accessory cryptic viruses to be investigated in the future.Plant mitoviruses belong to Mitoviridae family and consist of positive single-stranded RNA genomes replicating exclusively in host mitochondria. We previously reported the biological characterization of a replicating plant mitovirus, designated Chenopodium quinoa mitovirus 1 (CqMV1), in some Chenopodium quinoa accessions. In this study, we analyzed the mitochondrial proteome from leaves of quinoa, infected and not infected by CqMV1. Furthermore, by protein–protein interaction and co-expression network models, we provided a system perspective of how CqMV1 affects mitochondrial functionality. We found that CqMV1 is associated with changes in mitochondrial protein expression in a mild but well-defined way. In quinoa-infected plants, we observed up-regulation of functional modules involved in amino acid catabolism, mitochondrial respiratory chain, proteolysis, folding/stress response and redox homeostasis. In this context, some proteins, including BCE2 (lipoamide acyltransferase component of branched-chain alpha-keto acid dehydrogenase complex), DELTA-OAT (ornithine aminotransferase) and GR-RBP2 (glycine-rich RNA-binding protein 2) were interesting because all up-regulated and network hubs in infected plants; together with other hubs, including CAT (catalase) and APX3 (L-ascorbate peroxidase 3), they play a role in stress response and redox homeostasis. These proteins could be related to the higher tolerance degree to drought we observed in CqMV1-infected plants. Although a specific causative link could not be established by our experimental approach at this stage, the results suggest a new mechanistic hypothesis that demands further in-depth functional studies.

Physical Responses of Pinctada fucata to Salinity Stress

This study was conducted to understand the changes of physiological and biochemical indexes of black and red shell Pinctada fucata under acute high and low salt stress. In this study, the salinity of 35‰ was used as the control, while the salinities of 20 and 50% salinity were used as the low and high salt treatment groups, respectively. The osmotic pressure (OSM) and ion concentration in the hemolymph, Na+-K+ -ATPase (NKA) activity and respiratory metabolism in gills, and antioxidant and immune (non) enzymes in the hepatopancreas of P. fucata with two shell colors were compared and analyzed at the time periods of 1.5 and 3 h post-salinity stress. The results showed that the OSM and inorganic ion (Na+, Ca2+, and Cl–) concentration in the hemolymph of the black and red P. fucata increased significantly with the increase of salinity after the time periods of 1.5 and 3 h. At 3 h, the black P. fucata NKA activity decreased significantly with the increase of salinity, while red P. fucata reached the highest value at high salinity. The succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) activities of red P. fucata showed U-shaped and inverted U-shaped distributions with the increase of salinity after 1.5 h, respectively. With the increase of salinity, the phenoloxidase (POX) activity of red and black P. fucata showed inverted U-shaped and U-shaped distributions, respectively. The contents of glutathione (GSH) and vitamin C (VC) in black P. fucata decreased significantly with the increase of salinity at 1.5 and 3 h. Red P. fucata GSH and VC reached their maximum value in the 1.5-h low salinity group and 3-h high salinity group. The vitamin E (VE) content in black P. fucata increased significantly with the increase of salinity at 1.5 h, and reached the maximum at 3 h in the control group. Red P. fucata VE reached the maximum at 1.5 and 3 h in the control group. The results obtained from the present study revealed that the sensitivity of P. fucata to salinity varied in shell color. Compared to black P. fucata, red P. fucata responds more quickly to sharp salinity changes, thereby reducing more likely damage. Compared with a high salt environment, P. fucata was more adaptable to the changes of acute low salt environment. The results obtained from the present study provide the physical references for subsequent selective breeding of this species.

Leaflet Boron Concentration Reduced with Hybrid Pistacia vera Rootstocks

Excessive boron (B) in soil and water is a problem for pistachio (Pistacia vera L.) production in the San Joaquin Valley (SJV) of California. Although amenable, leaching of B requires more water than chlorine (Cl) or sodium (Na) and is increasingly difficult as B in irrigation water increases. The lack of subsurface drainage to the ocean increases soil salinity in many growing areas, especially on the west side of the SJV where B is often excessive natively in the soil and water. Pistachio rootstocks that can tolerate or exclude B may be a partial solution. For the past decade in California, the dominant rootstock has been seedlings and clonal selections of University of California Berkeley 1 (UCB-1), which is a hybrid of P. atlantica × P. integerrima. This reliance on a genetically similar pool of rootstocks has constrained Pistacia’s genetic potential for adapting to high-salt environments. This study compared scion and rootstock leaflet B concentration of novel hybrid experimental rootstocks with variable percentages of P. vera and P. integerrima heritage with UCB-1. Rootstocks with P. vera heritage limited B in both rootstock and scion leaflets compared with UCB-1. In six trials conducted over several years, leaflet B in ungrafted hybrid rootstocks having 62.5% to 75% P. vera and 25% to 37.5% P. integerrima heritage had 27.6% to 43.1% lower B leaflet concentration than did UCB-1. Depending on the experiment and year, grafted rootstocks having 37.5% P. vera and 62.5% P. integerrima heritage had 46.8% to 70.8% lower B scion leaflet concentration than did UCB-1. Genetic variation in B uptake in Pistacia species and interspecific hybrids, and among individual seedlings within populations, allows the breeding of pistachio rootstocks more tolerant of excess B.

A study on the salt attack performance of magnesium oxychloride cement in different salt environments

Anti-corrosion cement is urgently needed due to the rapid development of salt lake and marine engineering facilities, and ordinary Portland cement (OPC) concrete will undergo significant corrosion in salt environments. Due to its unique composition, magnesium oxychloride cement (MOC) has the potential to replace OPC in salt environments. In this work, the corrosion resistance of MOC in different salt environments was investigated. The results showed that the compressive strength and main hydration products in the MOC were stable in high salt environments. Moreover, the MOC exhibited excellent corrosion resistance in aging and raw brine solutions. In low salt environments, the compressive strength steadily decreased, and the main hydration products decomposed, indicating poor corrosion resistance in seawater and freshwater. In addition, the MOC mainly exhibited physical salt crystallization in high salt environments and chemical reactions in low salt environments.

Morphological and molecular characterization of plant growth promoting salt-tolerant bacteria associated with halophytes in the Southeast seaside of Vietnam

Halophytes are found in high-salt environments naturally, and their roots may be associated with promising microbial candidates for promoting crop growth and salt tolerance. In this study, halotolerant bacteria were isolated from soil and root samples of Rhizophora apiculate (R. apiculate), Avicennia ofcinalis (A. ofcinalis), Thespesia populnea (T. populnea), Acanthus ilicifolius (A. ilicifolius) and Trichophorum cespitosum (T. cespitosum), five native halophytes of southeast seaside of Vietnam. Isolates were tested for maximum salt tolerant and screened for the ability of phosphate solubilization and indole acetic acid (IAA) production. Colony morphology, pigmentation, and Gram staining of each IAA production halotolerant isolate were determined. The bacterial isolates showed the highest salt tolerance and IAA production were identifed by sequencing the 16S rRNA gene. A total of 54 isolates which were able to grow in the presence of up to NaCl 3M were isolated. Twenty-three halotolerant bacterial isolates had the capacity of IAA production, 60.9% from which were Gram positive with a cocci shape, colony in opaque/transparent yellow or opaque/off white, 1 - 2 mm or 2 - 3 mm in diameter with the convex surface. Three isolates VTDD1, VTTD2, and KGOR1 were able to solubilize insoluble phosphorus. The highest IAA production was observed in VTDR1 (93.77 µg/mL) followed by VTMR1 (75.23 µg/mL) and VTDR2 (60.00 µg/mL), while the smallest IAA production was observed in CGOD1 (0.50 µg/mL). The isolates VTDR1 and VTDR2 were identifed as Salinicola tamaricis (99.58% and 99.67% identity respectively), while VTMR1 was found to be Salinicola peritrichatus (98.37% identity).

Genetic and Comparative Genome Analysis of Exiguobacterium aurantiacum SW-20, a Petroleum-Degrading Bacteria with Salt Tolerance and Heavy Metal-Tolerance Isolated from Produced Water of Changqing Oilfield, China.

The genome of Exiguobacterium aurantiacum SW-20 (E. aurantiacum SW-20), a salt-tolerant microorganism with petroleum hydrocarbon-degrading ability isolated from the Changqing Oilfield, was sequenced and analyzed. Genomic data mining even comparative transcriptomics revealed that some genes existed in SW-20 might be related to the salt tolerance. Besides, genes related to petroleum hydrocarbon degradation discovered in genomic clusters were also found in the genome, indicating that these genes have a certain potential in the bioremediation of petroleum pollutants. Multiple natural product biosynthesis gene clusters were detected, which was critical for survival in the extreme conditions. Transcriptomic studies revealed that some genes were significantly up-regulated as salinity increased, implying that these genes might be related to the salt tolerance of SW-20 when living in a high salt environment. In our study, gene clusters including salt tolerance, heavy metal tolerance and alkane degradation were all compared. When the same functional gene clusters from different strains, it was discovered that the gene composition differed. Comparative genomics and in-depth analysis provided insights into the physiological features and adaptation strategies of E. aurantiacum SW-20 in the oilfield environment. Our research increased the understanding of niches adaption of SW-20 at genomic level.

Characterization of the Proteolytic Activity of a Halophilic Aspergillus reticulatus Strain SK1-1 Isolated from a Solar Saltern.

Salterns are hypersaline environments that are inhabited by diverse halophilic microorganisms, including fungi. In this study, we isolated a fungal strain SK1-1 from a saltern in the Republic of Korea, which was identified as Asperillus reticulatus. This is the first reported saline-environment-derived A. reticulatus that belongs to the Aspergillus penicillioides clade and encompasses xerophilic fungi. SK1-1 was halophilic, obligately requiring NaCl for growth, with a maximum radial growth of 6%–9% (w/v) NaCl. To facilitate the biotechnological application of halophilic fungi, we screened the SK1-1 strain for proteolytic activity. Proteases have widespread applications in food processing, detergents, textiles, and waste treatment, and halophilic proteases can enable protein degradation in high salt environments. We assessed the proteolytic activity of the extracellular crude enzyme of SK1-1 using azocasein as a substrate. The crude protease exhibited maximum activity at 40–50 °C, pH 9.5–10.5, and in the absence of NaCl. It was also able to retain up to 69% of its maximum activity until 7% NaCl. Protease inhibitor assays showed complete inhibition of the proteolytic activity of crude enzymes by Pefabloc® SC. Our data suggest that the halophilic A. reticulatus strain SK1-1 produces an extracellular alkaline serine protease.

Preparation and Performance Evaluation of Gemini Sulphobetaine Surfactant Bis{[(N-methyl-N-(3-alkoxy-2-hydroxy) propyl-N-(3-sulfonic) propyl] methylene}

Abstract Surfactants are very often used in tertiary oil production. However, the conventional surfactants cannot be used in high salinity reservoirs of tertiary oil production because the high salinity leads to the deactivation of the surfactants. Gemini sulpho-betaine surfactants have been developed to meet the requirements of tertiary oil production in such reservoirs. In this study, the Gemini sulphobetaine surfactant (bis{[(N-methyl-N-(3-alkoxy-2-hydroxy)propyl-N-(3-sulfonate)propyl]methylene}) was prepared by etherification, ring opening reaction and sulfonation reaction with decyl alcohol, epichlorohydrin, N,N’-dimethyl ethylene diamine and 1,3-propanesultone. The experimental conditions obtained are: the ratio of 1,3-propanesulfonic acid lactone to tertiary amine intermediate = 2.3 : 1, reaction temperature = 70°C and reaction time = 11 h. The analysis of the infrared spectrum showed that the structure of the synthesised substance corresponds to that of a Gemini sulphobetaine surfactant. The chemical shifts of the groups were determined by 1HNMR structural characterisation of the products. The surface tension, emulsifying properties, foaming properties and wetting properties were investigated. The results showed that the surfactant has good foaming properties and good compatibility in a high salt environment.

Response of microbial succession of Anammox granular sludge (AnGS) and essential abundance under salty stress and temperature reduction

This study explored the adaptive response of microbial community structure of anammox granular sludge (AnGS) and the recovery effect of biomass addition strategy under dual inhibitions of high salinity and low temperature. The results showed that, anammox process stable operated in a high-salt environment (18 g-NaCl L-1) at 35 °C, and the nitrogen removal rate (NRR) reached 0.60 kg-N m-3 d-1. The high salinity tolerance and recovery performance were attributed to the dominant functional bacteria genus Unclassified Candidatus Brocadiaceae selected by salinity. When the temperature dropped to 17 ℃, nitrogen accumulation (especially nitrite) could not be alleviated by simply reducing the substrate concentration. After adding 6 mL L-1 of sludge per day with an activity of 0.09 kg-N kg-VSS-1 d-1, nitrogen removal performance quickly recovered to 0.42 kg-N m-3 d-1 and reached 0.54 kg-N m-3 d-1 as the temperature recovered to 32 ℃. The abundance of 7.75E+10 copies g-SS-1 may be the primary value required by anammox bacteria in the adverse environment of high-salty and low-temperature.

Impacts of salt-tolerant Staphylococcus nepalensis 5-5 on bacterial composition and biogenic amines accumulation in fish sauce fermentation

High levels of biogenic amines (BAs) in fermented food can present a health risk to consumers. Microorganisms that can reduce BAs are widely used in fermented foods. However, the mechanism by which microorganisms reduce BAs in foods has not been explored. In this study, we investigated how Staphylococcus nepalensis 5-5 (S. nepalensis 5-5), which was a BA-degrading strain isolated from fish sauce, could reduce BA accumulation in the fish sauce. High-throughput sequencing and HPLC methods were sequentially used to determine the microbial community structure and BA content in fish sauce with/without S. nepalensis 5-5. The results showed that S. nepalensis 5-5 might be a safe strain that could improve the flavor of fish sauce while still exhibiting good BA degradation ability under a high salt environment. The content of BAs in fish sauce inoculated with S. nepalensis 5-5 was significantly decreased compared with the control fish sauce, achieving maximal reductions of 15.74, 14.18 and 16.65% in putrescine, cadaverine and histamine accumulation, respectively. According to high-throughput sequencing data, S. nepalensis 5-5 reduced the abundance of the genera positively associated with BAs, while increasing the number of bacterial genera negatively correlated with BAs in the sample and changed the correlation between some genera and BAs via species interaction. In addition, analysis of amino acid metabolism showed that S. nepalensis 5-5 might use histidine to produce metabolites other than histamine, thereby reducing the production of BAs. These findings not only explained the mechanisms by which the BA level in fish sauce could be reduced but also provided a potential means to control BA production in the fish sauce during the fermentation stage.

Deletion of the type IV secretion system promoter VirB in Brucella abortus A19 strain attenuated the virulence of the bacteria and promotes autophagy.

Brucella abortus is a gram-negative intracellular parasite bacteria that causes serious health hazards in humans and animals. The type IV secretion system (T4SS), encoded by the virB promoter, has been identified as an important virulence factor for Brucella abortus, but its impact on Brucella abortus A19 remains unclear. In this study, the T4SS of Brucella abortus A19 was inactivated by deletion of the virB promoter, resulting in a mutant strain A19ΔvirB. Real-time PCR and western blotting analysis demonstrated that T4SS-related proteins were not expressed after virB promoter deletion. Moreover, the survival rate of A19 in high-salt and strong acidic environments decreased after virB promoter deletion. Compared to the parental strain A19, the A19ΔvirB mutant strain showed reduced growth rate in TSB, decreased invasion ability to macrophages and dendritic cells, and reduced virulence of the mutant strain in macrophages, dendritic cells, and mice. In addition, the A19ΔvirB mutant strain showed enhanced autophagy in macrophages and dendritic cells compared with A19, and the A19ΔvirB mutant strain was able to upregulate IL-6 and downregulate IL-10 in macrophages. These data help us to better understand the T4SS of the A19 vaccine strain and contribute to our efforts to improve Brucella vaccines.

Corrosion Behavior of ASME SA-192 Steel Finned Tube by Wire Arc Spray in Temperature Control and High-Salt Environment

This paper proposes the corrosion behavior of ASME SA-192 steel finned tubes which were spray-coated with TH450 Chrome Nickel amorphous in a salt spray test chamber using 5% sodium chloride solution at a spraying speed of 12 mL/h according to The American Society of Testing and Materials (ASTM) B117 Standard. The salt spray test for 120 hours in the salt spray test in the chamber, the specimens that were exposed to moisture and salt fog in the surrounding air developed thin brown rust dots on the surface. The experimental results concluded that the specimens could withstand the corrosive environment for 5-15 years. The hardness test of coated specimens after the salt spray test for 480 hours showed that hardness and tensile strength of all specimens decreased due to surface damage from salt adsorption which resulted in blackish-brown rust and decreased tensile strength. Though, elongation of the coated specimens increased due to salt adsorption by the specimen surface, resulting in partial corrosion and rusting on the specimen surface. However, both parameters of the specimens exceed the ultimate tensile strength (UTS) standard test. Therefore, the spray coating with Chrome Nickel amorphous can increase the mechanical strength and corrosion resistance.

The Influence of Different Operation Conditions on the Treatment of Mariculture Wastewater by the Combined System of Anoxic Filter and Membrane Bioreactor.

The mariculture wastewater treatment performance for the combined system of anoxic filter and membrane bioreactor (AF-MBR) was investigated under different hydraulic retention times (HRTs), influent alkalinity, and influent ammonia nitrogen load. The results showed that the removal efficiencies of TOC and total nitrogen were slightly better at the HRT of 8 h than at other HRTs, and the phosphate removal efficiency decreased with the increase of HRT. With the increase of influent alkalinity, the removal of TOC and phosphate did not change significantly. With the increase of influent alkalinity from 300 mg/L to 500 mg/L, the total nitrogen removal efficiency of AF-MBR was improved, but the change of the removal efficiency was not obvious when the alkalinity increased from 500 mg/L to 600 mg/L. When the influent concentration of ammonia nitrogen varied from 20 mg/L to 50 mg/L, the removal efficiencies of TOC, phosphate, and total nitrogen by AF-MBR were stable. An interesting finding was that in all the different operation conditions examined, the treatment efficiency of AF-MBR was always better than that of the control MBR. The concentrations of NO3−-N in AF-MBR were relatively low, whereas NO3−-N accumulated in the control MBR. The reason was that the microorganisms attached to the carrier and remained fixed in the aerobic and anoxic spaces, so that there was a gradual enrichment of bacteria characterized by slow growth in a high-salt environment. In addition, the microorganisms could gather and grow on the carrier forming a biofilm with higher activity, a richer and more stable population, and enhanced ability to resist a load impact.

Research on Biological Fluidized Bed System Treatment Performance and Nitrogen Removal Process for Seafood Processing Wastewater with Different Operation Conditions

In this study, the biological fluidized bed system was used to treat seafood processing wastewater. The sludge was collected from the secondary sedimentation tank of a municipal wastewater treatment plant and acclimated for 200 days before the experiment. The treatment efficiencies of simulated seafood processing wastewater by biological fluidized bed system with different sludge concentrations, different hydraulic retention times (HRTs) and different bio-carriers were studied. The results showed that the removal efficiency of nitrogen and phosphorus increased with the increasing sludge concentration and by extending hydraulic retention time, and the higher removal efficiency of nitrogen and phosphorus could be obtained with the higher specific surface area of the bio-carrier. The nitrogen removal process analysis showed that the nitrification and denitrification activity of sludge could be changed with different operation conditions resulting in different nitrogen removal efficiency in the biological fluidized bed system. This was mainly because the change tendency of the ammonia nitrogen oxidizing process, nitrite oxidizing process, nitrite reduction process and nitrate reduction process was different with different operation conditions in a high salinity environment. Theoretically, the difference of the inhibitory effect of a high-salt environment on different nitrification and denitrification processes could be used to realize shortcut nitrification denitrification by controlling a certain operation condition.