Screening and Identification of a Strain of Heterotrophic Nitrification Bacteria and Its Application in Wastewater Treatment of Rural Farming

【Objective】Aiming at the problem of being difficult to treat the high concentration of NH4+-N in farming wastewater, one heterotrophic nitrification bacterium was isolated and screened from the lake sediment.【Method】The screened strains were subjected to Gram staining, scanning electron microscopy and strain identification. Homology analysis of 16SrDNA sequencing results was performed in the Blast database and phylogenetic trees were constructed. The heterotrophic nitrification and aerobic denitrification properties of this strain under different nitrogen sources were studied, and the denitrification characteristics were studied with different inoculum levels, carbon source, initial pH, temperature, C/N, and initial NH4+-N concentration as environmental factors. Finally, the strain was added to the actual rural pig wastewater to evaluate its application ability.【Result】The strain of heterotrophic nitrification strain was identified as Acinetobacter sp and named L-1. Univariate experiments showed that L-1 had the best heterotrophic nitrification effect under inoculation ratio of 2%, carbon source of sodium citrate, pH 6-9, temperature 20-30 ℃, C/N 10-20, and NH4+-N initial concentration of 50 mg/L. In the actual pig wastewater, L-1 was added to the wastewater for nitrogen removal, in which the 1 000 mg/L NH4+-N wastewater was reduced to 298.46 mg/L at the 96th hour. The removal rate of NH4+-N reached 70.15%, which was 45.78% higher than that of the blank control group, while both concentrations of NO3--N and NO2--N were decreased.【Conclusion】The strain L-1 has the ability of heterotrophic nitrification and aerobic denitrification, which has certain reference value in the study of heterotrophic nitrification bacteria for the treatment of pig wastewater

The Role of Myeloid-Derived Suppressor Cells in the Treatment of Pancreatic Cancer

Pancreatic cancer has the highest mortality rate of all major cancers, with a 5-year survival rate of about 10%. Early warning signs and symptoms of pancreatic cancer are vague or nonexistent, and most patients are diagnosed in Stage IV, when surgery is not an option for about 80%–85% of patients. For patients with inoperable pancreatic cancer, current conventional treatment modalities such as chemotherapy and radiotherapy (RT) have suboptimal efficacy. Tumor progression is closely associated with the tumor microenvironment, which includes peripheral blood vessels, bone marrow-derived inflammatory cells, fibroblasts, immune cells, signaling molecules, and extracellular matrix. Tumor cells affect the microenvironment by releasing extracellular signaling molecules, inducing peripheral immune tolerance, and promoting tumor angiogenesis. In turn, the immune cells of the tumor affect the survival and proliferation of cancer cells. Myeloid-derived suppressor cells are key cellular components in the tumor microenvironment and exert immunosuppressive functions by producing cytokines, recognizing other immune cells, and promoting tumor growth and metastasis. Myeloid-derived suppressor cells are the main regulator of the tumor immune response and a key target for tumor treatments. Since the combination of RT and immunotherapy is the main strategy for the treatment of pancreatic cancer, it is very important to understand the immune mechanisms which lead to MDSCs generation and the failure of current therapies in order to develop new target-based therapies. This review summarizes the research advances on the role of Myeloid-derived suppressor cells in the progression of pancreatic cancer and its treatment application in recent years