[Background] Indigoidine is a nontoxic blue pigment produced by microorganisms. [Objective] Comparison of the stability of heterologous expressed indigoidine in Escherichia coli and commercial indigo. [Methods] Recombinant E. coli DH5α/p28s strain was constructed to produce indigoidine. The effects of light, UV, pH, temperature, oxidant, reductant, food additive, metal ion on the stability of the two pigments were investigated. [Results] When N,N-dimethylformamide (DMF) was used as solvent, both indigoidine and indigo were sensitive to visible light and UV. The colors of the two pigments were stable at pH 1.0?11.0, but higher pH had a great destructive effect. The tolerance of indigoidine to Vc reduction was stronger than that of indigo. Both maximal absorption values were reduced at a certain degree by oxidant. Indigoidine showed distinguished better thermal stability than indigo below 75 °C, but both were bleached at higher temperature. The food additive citric acid and benzoic acid had significant protective effect on the stability of indigoidine and indigo respectively. Ca2+ and Mg2+ showed certain color-keeping effect on both pigments, while Na+, K+ and Li+ had no overall destruction impact, but Zn2+, Al3+, Cu2+, Fe2+ and Fe3+ exhibited notable destruction on both. [Conclusion] Indigoidine exhibits much better overall stability than indigo, suggesting a broader prospect of development and application.
[Background] Biological aerated filter performs well on organic matter and ammonia nitrogen removal, whereas exhibits bad on phosphorus removal. [Objective] To improve the phosphorus removal efficiency of the BAF system. [Methods] The experimental group was an A/O filter, followed by a limestone-filling filter column. The control group was an identical one only without limestone filter. The treatment efficiency of reflux BAF system in experimental group and control group was compared and analyzed. Additionally, based on MPN method and high-throughput sequencing technology, the nitrifying bacteria quantity and microbial community structure in aerobic column were also investigated. [Results] Comparative tests showed that, compared with the BAF system without reflux, the removal efficiency of the reflux BAF system for COD, NH4+-N, TN, and TP increased by 3.16%, 41.21%, 40.62% and 18.93%, respectively. The removal efficiency of COD, NH4+-N, TN and TP in the experimental group increased by 1.75%, 2.3%, 2.2% and 23.1%, respectively. According to the results of high-throughput sequencing, the abundance of Proteobacteria, Actinobacteria, Firmicutes, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Xanthomonadaceae in the aerobic filter column of the experimental group increased by 25.2%, 4.8%, 5.5%, 7.4%, 7.3%, 12.0% and 6.6%, respectively, compared with the control group. Meanwhile, the amount of different species between the experimental group and the control group at the genus level was 170. [Conclusion] The removal efficiency of TN and TP could be significantly improved by the reflux of limestone filter column. Calcium ions could improve the removal efficiency of phosphorus by chemical precipitation, and enhance the effect of biological phosphorus removal by improving the structure of bacteria in aerobic column.
[Background] Trichoderma asperellum agent has been widely used in biological control and secondary bioremediation of soil secondary salinization, while less is known about the salt-tolerant mechanism and salt accumulation potential of this strain under stress of salinization. [Objective] This research aimed to reveal the physiological response of Trichoderma asperellum CTCCSJ-W-SBW10264 (T264) to Na+-induced oxidative stress and the Na+ adsorption and accumulation characteristics of this strain. [Methods] Gradient concentrations of Na+ in broth were designed as stress factor in fermentation experiment of strain T264, then mycelia samples at different culture stages were collected for the measurement of cell oxidative damage indices including H2O2 content and malondialdehyde (MDA) level together with the activity of cellular antioxidant related enzymes. [Results] Result of Na+ stress cultivation experiment indicated that T264 could survive with Na+ concentration of 1.22 mol/L, and the growth of T264 was not significantly inhibited with Na+ concentration lower than 0.25 mol/L. The results of study on oxidative damage and oxidative damage responses revealed that the higher Na+ concentration lead to the higher cellular oxidation level (MDA content). Moreover, with the accumulation of MDA and H2O2 in hyphae of T264, the activity of antioxidative damage enzymes in cells was also increased significantly. After Na+ treatment for 24 h, the activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) were respectively highest under the Na+ stress of 0.5, 1.0 and 1.22 mol/L, respectively, which were 36.66, 3.34 and 233.3 U/mg. The experimental results of Na+ adsorption and accumulation characteristics showed that hyphae of T264 had a strong adsorption capacity for Na+. After being cultured in the 0.05 mol/L Na+ environment for 72 h, the surface Na+ adsorption capacity of mycelia was 1 347.6 mg/g, and the internal Na+ accumulation capacity of mycelia was 218.6 mg/g. The remove rate of Na+ in the culture medium reached 32% through surface adsorption and internal accumulation of T264 mycelia. [Conclusion] This experiment showed that the antioxidant damage-related enzymes of T264 play an important role in its resistance to Na+ stress, and the strain T264 has a strong adaptability to high concentration of Na+ and an efficient adsorption and accumulation effect of Na+ in the environment.
[Background] Pseudomonas chlororaphis HT66 is a plant growth-promoting rhizobacterium (PGPR) with biocontrol safety and high yield of phenazine-1-carboxamide (PCN). It has broad application prospects in biological control, ecological agriculture and sustainable agriculture. SuhB, a small non-coding RNA, involved in the metabolic regulation of multiple processes in cells. [Objective] This study explored the effect of suhB gene on the biocontrol ability of in P. chlororaphis HT66. [Methods] we constructed the suhB deletion mutant HT66ΔsuhB by homologous recombination method and the suhB complemented mutant HT66ΔsuhB-pBBR-suhB by plasmid. They were used to explore the effect of suhB gene on strain growth, biofilm formation, swarming motility and PCN synthesis. [Results] The mutant HT66ΔsuhB grew slowly, the plateau period delayed by 12 h and its biomass decreased to 61.6% of the wild type. The maximum yield of mutant strain in KMB medium can reach 109.5 mg/g (per DCW), which was 2.1 times that of wild type. The biofilm formation increased significantly, which was 1.8 times that of the wild type. However, the swarming motility of HT66ΔsuhB was defective. On the swarm plate, the movement radius of the wild strain was 21 mm, while the movement radius of the mutant strain was 9.7 mm. The suhB gene complemented mutant is similar to wild type in the above aspects. Compared with the wild type, there is no difference on the expression of phzI at the overall level in mutant HT66ΔsuhB. On the contrary, the expression of phzR increased significantly, which is 3.1 times that of the wild type. In addition, the expression of phzAp at the transcriptional level is 1.8 times that of the wild type. [Conclusion] The regulation of suhB gene in P. chlororaphis HT66 participates in the growth, biofilm formation, swarming motility and PCN synthesis. This research provides a theoretical basis for the metabolic transformation and biocontrol applications of P. chlororaphis HT66.
Start Publication in 1974Released on the 20th per monthResponsible institution: Chinese Academy of SciencesSponsored by: Institute of Microbiology, CASChinese Society for MicrobiologyEditor-in-Chief: HE Rong-QiaoEditorial office: Tel: +86-10-64807511E-mail: email@example.com