Temporal dynamics of stress response in Halomonas elongata to NaCl shock: physiological, metabolomic, and transcriptomic insights.

BACKGROUND: The halophilic bacterium Halomonas elongata is an industrially important strain for ectoine production, with high value and intense research focus. While existing studies primarily delve into the adaptive mechanisms of this bacterium under fixed salt concentrations, there is a notable dearth of attention regarding its response to fluctuating saline environments. Consequently, the stress response of H. elongata to salt shock remains inadequately understood. RESULTS: This study investigated the stress response mechanism of H. elongata when exposed to NaCl shock at short- and long-time scales. Results showed that NaCl shock induced two major stresses, namely osmotic stress and oxidative stress. In response to the former, within the cell's tolerable range (1-8% NaCl shock), H. elongata urgently balanced the surging osmotic pressure by uptaking sodium and potassium ions and augmenting intracellular amino acid pools, particularly glutamate and glutamine. However, ectoine content started to increase until 20 min post-shock, rapidly becoming the dominant osmoprotectant, and reaching the maximum productivity (1450 ± 99 mg/L/h). Transcriptomic data also confirmed the delayed response in ectoine biosynthesis, and we speculate that this might be attributed to an intracellular energy crisis caused by NaCl shock. In response to oxidative stress, transcription factor cysB was significantly upregulated, positively regulating the sulfur metabolism and cysteine biosynthesis. Furthermore, the upregulation of the crucial peroxidase gene (HELO_RS18165) and the simultaneous enhancement of peroxidase (POD) and catalase (CAT) activities collectively constitute the antioxidant defense in H. elongata following shock. When exceeding the tolerance threshold of H. elongata (1-13% NaCl shock), the sustained compromised energy status, resulting from the pronounced inhibition of the respiratory chain and ATP synthase, may be a crucial factor leading to the stagnation of both cell growth and ectoine biosynthesis. CONCLUSIONS: This study conducted a comprehensive analysis of H. elongata's stress response to NaCl shock at multiple scales. It extends the understanding of stress response of halophilic bacteria to NaCl shock and provides promising theoretical insights to guide future improvements in optimizing industrial ectoine production.

Bioemulsification and Microbial Community Reconstruction in Thermally Processed Crude Oil.

Utilization of low-cost, environmental-friendly microbial enhanced oil recovery (MEOR) techniques in thermal recovery-processed oil reservoirs is potentially feasible. However, how exogenous microbes facilitate crude oil recovery in this deep biosphere, especially under mesophilic conditions, is scarcely investigated. In this study, a thermal treatment and a thermal recurrence were processed on crude oil collected from Daqing Oilfield, and then a 30-day incubation of the pretreated crude oil at 37 °C was operated with the addition of two locally isolated hydrocarbon-degrading bacteria, Amycolicicoccus subflavus DQS3-9A1T and Dietzia sp. DQ12-45-1b, respectively. The pH, surface tension, hydrocarbon profiles, culture-dependent cell densities and taxonomies, and whole and active microbial community compositions were determined. It was found that both A. subflavus DQS3-9A1T and Dietzia sp. DQ12-45-1b successfully induced culture acidification, crude oil bioemulsification, and residual oil sub-fraction alteration, no matter whether the crude oil was thermally pretreated or not. Endogenous bacteria which could proliferate on double heated crude oil were very few. Compared with A. subflavus, Dietzia sp. was substantially more effective at inducing the proliferation of varied species in one-time heated crude oil. Meanwhile, the effects of Dietzia sp. on crude oil bioemulsification and hydrocarbon profile alteration were not significantly influenced by the ploidy increasing of NaCl contents (from 5 g/L to 50 g/L), but the reconstructed bacterial communities became very simple, in which the Dietzia genus was predominant. Our study provides useful information to understand MEOR trials on thermally processed oil reservoirs, and proves that this strategy could be operated by using the locally available hydrocarbon-degrading microbes in mesophilic conditions with different salinity degrees.

Recent advances in microbial capture of hydrogen sulfide from sour gas via sulfur-oxidizing bacteria.

Biological desulfurization offers several remarkably environmental advantages of operation at ambient temperature and atmospheric pressure, no demand of toxic chemicals as well as the formation of biologically re-usable sulfur (S0), which has attracted increasing attention compared to conventionally physicochemical approaches in removing hydrogen sulfide from sour gas. However, the low biomass of SOB, the acidification of process solution, the recovery of SOB, and the selectivity of bio-S0 limit its industrial application. Therefore, more efforts should be made in the improvement of the BDS process for its industrial application via different research perspectives. This review summarized the recent research advances in the microbial capture of hydrogen sulfide from sour gas based on strain modification, absorption enhancement, and bioreactor modification. Several efficient solutions to limitations for the BDS process were proposed, which paved the way for the future development of BDS industrialization.

Thermodynamically favorable reactions shape the archaeal community affecting bacterial community assembly in oil reservoirs.

Microbial community assembly mechanisms are pivotal for understanding the ecological functions of microorganisms in biogeochemical cycling in Earth's ecosystems, yet rarely investigated in the context of deep terrestrial ecology. Here, the microbial communities in the production waters collected from water injection wells and oil production wells across eight oil reservoirs throughout northern China were determined and analyzed by proportional distribution analysis and null model analysis. A 'core' microbiota consisting of three bacterial genera, including Arcobacter, Pseudomonas and Acinetobacter, and eight archaeal genera, including Archaeoglobus, Methanobacterium, Methanothermobacter, unclassified Methanobacteriaceae, Methanomethylovorans, Methanoculleus, Methanosaeta and Methanolinea, was found to be present in all production water samples. Canonical correlation analysis reflected that the core archaea were significantly influenced by temperature and reservoir depth, while the core bacteria were affected by the combined impact of the core archaea and environmental factors. Thermodynamic calculations indicate that bioenergetic constraints are the driving force that governs the enrichment of two core archaeal guilds, aceticlastic methanogens versus hydrogenotrophic methanogens, in low- and high-temperature oil reservoirs, respectively. Collectively, our study indicates that microbial community structures in wells of oil reservoirs are structured by the thermodynamic window of opportunity, through which the core archaeal communities are accommodated directly followed by the deterministic recruiting of core bacterial genera, and then the stochastic selection of some other microbial members from local environments. Our study enhances the understanding of the microbial assembly mechanism in deep terrestrial habitats. Meanwhile, our findings will support the development of functional microbiota used for bioremediation and bioaugmentation in microbial enhanced oil recovery.

Efficient degradation of rhodamine B using modified graphite felt gas diffusion electrode by electro-Fenton process.

The electro-Fenton (EF) process treatment of 0.1-M (rhodamine B) RhB solution was studied with different graphite cathode materials, and graphite felt (GF) was selected as a promising material in further investigation. Then, the degradation performances of gas diffusion electrode (GDE) and graphite felt (GF) were compared, and GDE was confirmed to be more efficient in RhB removal. The operational parameters such as Fe(2+) dosage and current density were optimized, and comparison among different modified methods-polytetrafluoroethylene-carbon black (PTFE-CB), polytetrafluoroethylene-carbon nanotube (PTFE-CNT), electrodeposition-CB, and electrodeposition-CNT-showed 98.49 % RhB removal by PTFE-CB-modified cathode in 0.05 M Na2SO4 at a current density of 50 A/m(2) and an air flow rate of 1 L/min after 20 min. Meanwhile, after cathode modified by PTFE-CB, the mineralization efficiency and mineralization current efficiency performed absolutely better than the pristine one. Cyclic voltammograms, SEM images, contact angles, and BET surface area were carried out to demonstrate stronger current responses and higher hydrophilicity of GF after modified. The value of biochemical oxygen demand/chemical oxygen demand (BOD5/COD) increased from 0.049 to 0.331 after 90-min treatment, suggesting the solution was biodegradable, and the modified cathode was confirmed to be stable after ten circle runs. Finally, a proposed degradation pathway of RhB was put forward.

SiRNA-phospholipid conjugates for gene and drug delivery in cancer treatment.

Due to low charge density and stiff backbone structure, small interfering RNA (siRNA) has inherently poor binding ability to cationic polymers and lipid carriers, which results in low siRNA loading efficiency and limits siRNA success in clinical application. Here, siRNA-phospholipids conjugates are developed, which integrate the characteristics of the two phospholipids to self-assemble via hydrophilic siRNA and hydrophobic phospholipid tails to overcome the siRNA's stiff backbone structures and enhance the siRNA loading efficiency. In this study, the thiol-modified sense and antisense siRNA are chemically conjugated with phospholipids to form sense and antisense siRNA-phospholipid, and then these sense or antisense siRNA-phospholipids with equal amounts are annealed to generate siRNA-phospholipids. The siRNA-phospholipids can serve dual functions as agents that can silence gene expression and as a component of nanoparticles to embed hydrophobic anticancer drugs to cure tumor. siRNA-phospholipids together with cationic lipids and DSPE-PEG2000 fuse around PLGA to form siRNA-phospholipids enveloped nanoparticles (siRNA-PCNPs), which can deliver siRNAs and hydrophobic anticancer drugs into tumor. In animal models, intravenously injected siRNA-PCNPs embedded DOX (siPlk1-PCNPs/DOX) is highly effective in inhibiting tumor growth. The results indicate that the siRNA-PCNPs can be potentially applied as a safe and efficient gene and anticancer drug delivery carrier.

Bio-desulfurization and denitrification by anaerobic-anoxic process for the treatment of wastewater from flue gas washing.

For amine-based carbon dioxide capture, nitrogen oxides and sulfur oxides were the main pollutants that had a negative effect on the regeneration of solvent. Before carbon dioxide capture, the sulfur oxides in flue gas should be removed by the method of calcium salt, and then washed by alkaline solution to eliminate the residual nitrogen oxides and sulfur oxides. The washing wastewater containing sulfate and nitrate needs to be treated. In this study, a novel anaerobic-anoxic process was built up for the treatment of this washing wastewater. Nitrate was reduced to nitrogen by denitrifying bacteria. Sulfate was firstly reduced to sulfide by sulfate reducing bacteria, and then selectively oxidized to element sulfur by sulfide oxidizing bacteria. The treated liquid could be reused as absorption after the adjustment of pH value. The performances of this bioprocess were investigated under various pH values and S/N ratios. It was found that the optimal pH value of influent was 6.0, the percentages of denitrification and sulfate reducing could reach 90 and 89%, respectively. Seventy-six percent of sulfate was transformed into element sulfur. Nitrate significantly had a negative effect on sulfate reduction above 10 mM. As 20 mM nitrate, the sulfate reducing percentage would drop to 67%. These results showed that the anaerobic-anoxic process was feasible for the treatment of flue gas washing wastewater. It would be prospectively applied to other wastewater with the higher ratio of SO4(2-)/NO3(-).

Bio-oil based biorefinery strategy for the production of succinic acid.

BACKGROUND: Succinic acid is one of the key platform chemicals which can be produced via biotechnology process instead of petrochemical process. Biomass derived bio-oil have been investigated intensively as an alternative of diesel and gasoline fuels. Bio-oil could be fractionized into organic phase and aqueous phase parts. The organic phase bio-oil can be easily upgraded to transport fuel. The aqueous phase bio-oil (AP-bio-oil) is of low value. There is no report for its usage or upgrading via biological methods. In this paper, the use of AP-bio-oil for the production of succinic acid was investigated. RESULTS: The transgenic E. coli strain could grow in modified M9 medium containing 20 v/v% AP-bio-oil with an increase in OD from 0.25 to 1.09. And 0.38 g/L succinic acid was produced. With the presence of 4 g/L glucose in the medium, succinic acid concentration increased from 1.4 to 2.4 g/L by addition of 20 v/v% AP-bio-oil. When enzymatic hydrolysate of corn stover was used as carbon source, 10.3 g/L succinic acid was produced. The obtained succinic acid concentration increased to 11.5 g/L when 12.5 v/v% AP-bio-oil was added. However, it decreased to 8 g/L when 50 v/v% AP-bio-oil was added. GC-MS analysis revealed that some low molecular carbon compounds in the AP-bio-oil were utilized by E. coli. CONCLUSIONS: The results indicate that AP-bio-oil can be used by E. coli for cell growth and succinic acid production.

Metallofullerol nanoparticles with low toxicity inhibit tumor growth by induction of G0/G1 arrest.

AIMS: [Gd@C(82)(OH)(22)](n) is a new type of nanoparticle with potent antineoplastic activity and low toxicity compared with traditional drugs. In this study, we explored, for the first time, the effect of [Gd@C(82)(OH)(22)](n) on the cell cycle using human breast cancer MCF-7 and human umbilical vein endothelial ECV304 cell lines by flow cytometry. METHODS: Cell viability was assessed through CCK-8 assay, and MCF-7 tumor-bearing mice were examined after 2 weeks of treatment with [Gd@C(82)(OH)(22)](n). Cell cycle-related gene expression was detected by microarray and confirmed by real-time PCR and RNAi. RESULTS: Cell viability studies confirmed that [Gd@C(82)(OH)(22)](n) inhibits breast cancer effectively with very low toxicity. Flow cytometric data and microarray results reveal that [Gd@C(82)(OH)(22)](n) mediates G0/G1 arrest in both cell lines by regulating the expression of several genes, such as cyclin D2, cyclin E and CDK4, among others, in the related cell cycle. CONCLUSION: Results further demonstrated that [Gd@C(82)(OH)(22)](n) could inhibit tumor growth by inducing tumor cell and vein endothelial cell G0/G1 arrest, which may explain the low toxicity of [Gd@C(82)(OH)(22)](n).

Epigenetic modulation of human breast cancer by metallofullerenol nanoparticles: in vivo treatment and in vitro analysis.

Multi-hydroxylated endohedral metallofullerenol [Gd@C(82)(OH)(22)](n) nanoparticles possess the general physico-chemical characteristics of most nanoparticles. They also exhibit uniquely low toxicity and antineoplastic efficacy. In the current study, the molecular mechanisms and epigenetic characteristics of the antineoplastic action of these nanoparticles are explored. Human breast cancer MCF-7 and human umbilical vein endothelial ECV304 cell lines were used. Cell viability assay, cell hierarchical cluster analysis by cDNA microarray, semi-quantitative reverse transcription-polymerase chain reaction and Western blot analysis were conducted to investigate the changes in molecular and cellular signaling pathways caused by [Gd@C(82)(OH)(22)](n). The results demonstrated the high antitumor activity and low cytotoxicity of [Gd@C(82)(OH)(22)](n) nanoparticles both in vivo and in vitro. Their possible anti-tumor mechanisms were also discussed. The present study may provide new insight into the mechanism of action of these nanoparticles.

Subcutaneous injection of water-soluble multi-walled carbon nanotubes in tumor-bearing mice boosts the host immune activity.

The immunological responses induced by oxidized water-soluble multi-walled carbon nanotubes on a hepatocarcinoma tumor-bearing mice model via a local administration of subcutaneous injection were investigated. Experimental results show that the subcutaneously injected carbon nanotubes induced significant activation of the complement system, promoted inflammatory cytokines' production and stimulated macrophages' phagocytosis and activation. All of these responses increased the general activity of the host immune system and inhibited the progression of tumor growth.

Recovery and purification of nicotine from waste tobacco by aqueous two-phase system/reverse extraction.

A two-step process has been developed for the purification of nicotine from waste tobacco using an aqueous two-phase system and solvent reverse extraction. The partitioning behavior of nicotine was investigated in an isopropyl alcohol/(NH4)2SO4 aqueous two-phase system. The effects of the addition of salt, pH and temperature on the partitioning behavior of nicotine were studied. The recovery rate of nicotine was 96.1% with a purity of above 99% when optimal conditions were used [(NH4)2SO4 25%, pH 9, temperature 35 degrees C, isopropyl alcohol 5 mL].

Green tea (Camellia sinensis) and cancer prevention: a systematic review of randomized trials and epidemiological studies.

BACKGROUND: Green tea is one of the most popular beverages worldwide. This review summarizes the beneficial effects of green tea on cancer prevention. METHODS: Electronic databases, including PubMed (1966-2008), the Cochrane Library (Issue 1, 2008) and Chinese Biomedical Database (1978-2008) with supplement of relevant websites, were searched. There was no language restriction. The searches ended at March 2008. We included randomized and non-randomized clinical trials, epidemiological studies (cohort and case-control) and a meta-analysis. We excluded case series, case reports, in vitro and animal studies. Outcomes were measured with estimation of relative risk, hazard or odd ratios, with 95% confidence interval. RESULTS: Forty-three epidemiological studies, four randomized trials and one meta-analysis were identified. The overall quality of these studies was evaluated as good or moderate. While some evidence suggests that green tea has beneficial effects on gastrointestinal cancers, the findings are not consistent. CONCLUSION: Green tea may have beneficial effects on cancer prevention. Further studies such as large and long term cohort studies and clinical trials are warranted.