Enhanced chromium and nitrogen removal by constructing a biofilm reaction system based on denitrifying bacteria preferential colonization theory.

Understanding the developmental characteristics of microbial communities in biofilms is crucial for designing targeted functional microbial enhancements for the remediation of complex contamination scenarios. The strong prioritization effect of microorganisms confers the ability to colonize strains that arrive first dominantly. In this study, the auto-aggregating denitrifying bacterial Pseudomonas stutzeri strain YC-34, which has both nitrogen and chromium removal characteristics, was used as a biological material to form a stable biofilm system based on the principle of dominant colonization and biofortification. The effect of the biofilm system on nitrogen and chromium removal was characterized by measuring the changes in the quality of influent and effluent water. The pattern of biofilm changes was analyzed by measuring biofilm content and thickness and characterizing extracellular polymer substances (EPS). Further analysis of the biofilm microbiota characteristics and potential functions revealed the mechanism of strain YC-34 biofortified biofilm. The results revealed that the biofilm system formed could achieve 90.56% nitrate-nitrogen removal with an average initial nitrate-nitrogen concentration of 51.9 mg/L and 40% chromium removal with an average initial hexavalent chromium Cr(VI) concentration of 7.12 mg/L. The biofilm properties of the system were comparatively analyzed during the biofilm formation period, the fluctuation period of Cr(VI)-stressed water quality, and the stabilization period of Cr(VI)-stressed water quality. The biofilm system may be able to increase the structure of hydrogen bonds, the type of protein secondary structure, and the abundance of amino acid-like components in the EPS, which may confer biofilm tolerance to Cr(VI) stress and allow the system to maintain a stable biofilm structure. Furthermore, microbial characterization indicated an increase in microbial diversity in the face of chromium stress, with an increase in the abundance of nitrogen removal-associated functional microbiota and an increasing trend in the abundance of nitrogen transfer pathways. These results demonstrate that the biofilm system is stable in nitrogen and chromium removal. This bioaugmentation method may provide a new way for the remediation of heavy metal-polluted water bodies and also provides theoretical and application parameters for the popularization and application of biofilm systems.

Nitrogen removal intensification of biofilm through bioaugmentation with Methylobacterium gregans DC-1 during wastewater treatment.

The increasing concern for environmental remediation has led to a search for effective methods to remove eutrophic nutrients. In this study, Methylobacterium gregans DC-1 was utilized to improve nitrogen removal in a sequencing batch biofilm reactor (SBBR) via aerobic denitrification. This bacterium has the extraordinary characteristics of strong auto-aggregation and a high ability to remove nitrogen efficiently, making it an ideal candidate for enhanced treatment of nitrogen-rich wastewater. This strain was used for the bioassessment of a test reactor (SBBRbio), which showed a shorter biofilm formation time compared to a control reactor (SBBRcon) without this strain inoculation. Moreover, the enhanced biofilm was enriched in TB-EPS and had a wider variety of protein secondary structures than SBBRcon. During the stabilization phase of SBBRbio, the EPS molecules showed the highest proportion of intermolecular hydrogen bonding. It is possible that bioaugmentation with this strain positively affects the structural stability of biofilm. At influent ammonia loadings of 100 and 150 mg. L-1, the average reduction of ammonia and nitrate-nitrogen was higher in the experimental system compared to the control system. Additionally, nitrite-N accumulation was lower and N2O production decreased compared to the control. Analysis of the microbial community structure demonstrated successful colonization in the bioreactor by a highly nitrogen-tolerant strain that efficiently removed inorganic nitrogen. These results illustrate the great potential of this type of denitrifying bacteria in the application of bioaugmentation systems.

Characteristics of pain sensitivity in children and model mice with autism spectrum disorder disorders / 中国学校卫生

Objective@#To explore the characteristics of pain sensitivity of autism spectrum disorder (ASD), and to provide reference for clinical comprehensive intervention of ASD.@*Methods@#A case-control study was conducted to investigate the characteristics of pain sensitivity in 142 ASD children and 142 normal children using the items related to pain sensitivity in the Autism Treatment Evaluation Checklist (ATEC). In addition, two recognized ASD model mice (BTBR mice and model mice induced by VPA) were selected as experimental group. The thermal pain threshold and mechanical pain threshold of BTBR mice were measured by electroshock seizure threshold and Von Frey filament test, and the differences of pain characteristics between BTBR mice and control mice were compared, the thermal pain threshold of model mice induced by VPA (VPA rats) was measured by electroshock seizure threshold, and the differences between BTBR mice and control mice (Con) were compared.@*Results@#There was significant difference in pain sensitivity between ASD group and control group (χ 2=0.81，P<0.05), and the sensitivity of ASD children to pain was significantly lower than that of normal control children. The pain sensitivity of BTBR mice and C57BL/6 mice on the 42 nd day after birth was measured. The T-test analysis showed that the time taken for BTBR and C57BL/6 mice to retract their feet on the 42 nd day after birth (3.62±0.38,3.02±0.33)s (t=3.28,P<0.01), and the mechanical pain threshold (9.75±3.58,0.55±0.93)s (t=7.44,P<0.01). The detection of thermal stinging pain in VPA rats and con rats on the 9 th, 11 th, 13 th and 15 th day after birth was detected. The results of t test were as follows:P9(11.34±1.38,9.81±1.64)g, P11(11.37±1.98,9.36±1.11)g, P13(11.53±1.38,9.51±1.01)g and P15(12.05±2.91,8.74±1.60)g (t=-2.79,-2.25,3.95,3.95,P<0.05).@*Conclusion@#Compared with normal control children, ASD children show insensitivity to pain which is further supported by two types of animal models for ASD.