Ammonia oxidation microorganisms generally tend to have low rates of ammonia oxidation under acidic conditions, as the protonated ammonia is not a substrate for ammonia monooxygenase. In this work, heterotrophic ammonia oxidation bacteria (HAOB) Pseudomonas citronellolis strain YN-21 showed high efficiency in removing NH4+ (12.7 mg/L/h) even at initial pH 4.5. The potential acid resistance mechanisms (H+ efflux, H+ consumption, and production of alkaline substances) maintained intracellular pH neutrality. Transcriptome analysis showed that genes involved in amino acid metabolism, carbohydrate metabolism, ABC transporter and nitrogen metabolism were significantly up-regulated, which facilitated the rapid removal of NH4+ in an acidic environment. Moreover, urea could be used as an alternative nitrogen source for YN-21 in a strongly acidic environment, and the production of NH3 from urea hydrolysis provided a substrate for ammonia oxidation. These results provide new insights into efficient ammonia oxidation in acidic environments.

Heterotrophic nitrifying bacteria are found to be promising candidates for implementation in wastewater treatment systems due to their tolerance to extreme environments. A novel acid-resistant bacterium, Pseudomonas citronellolis YN-21, was isolated and reported to have exceptional heterotrophic nitrification capabilities in acidic condition. At pH 5, the highest NH4+ removal rate of 7.84 mg/L/h was displayed by YN-21, which was significantly higher than the NH4+ removal rates of other strains in neutral and alkaline environments. Remarkably, a distinct accumulation of NH2OH and NO3- was observed during NH4+ removal by strain YN-21, while traditional amo and hao genes were not detected in the genome, suggesting the possible presence of alternative nitrifying genes. Moreover, excellent nitrogen removal performance was displayed by YN-21 even under high concentrations of metal ion stress. Consequently, a broad application prospect in the treatment of leather wastewater and mine tailwater is offered by YN-21.

The wide use of ZnO and CuO nanoparticles in research, medicine, industry, and other fields has raised concerns about their biosafety. It is therefore unavoidable to be discharged into the sewage treatment system. Due to the unique physical and chemical properties of ZnO NPs and CuO NPs, it may be toxic to the members of the microbial community and their growth and metabolism, which in turn affects the stable operation of sewage nitrogen removal. This study summarizes the toxicity mechanism of two typical metal oxide nanoparticles (ZnO NPs and CuO NPs) to nitrogen removal microorganisms in sewage treatment systems. Furthermore, the factors affecting the cytotoxicity of metal oxide nanoparticles (MONPs) are summarized. This review aims to provide a theoretical basis and support for the future mitigating and emergent treatment of the adverse effects of nanoparticles on sewage treatment systems.

花椒(Zanthoxylum armatum)开黄花后不能正常结实,严重影响了相关产业发展.为探究花椒开黄花的生理特点及其防治关键药剂,本研究对不同时期花椒形态进行了观察,对多种植物激素含量进行了测定测定.以重庆多地九叶青花椒(Z.armatum var.novemfolius)正常株和黄花株为试材,采用石蜡切片法对花椒形态进行观察并对花椒黄花株和正常株花叶数量质量进行统计,采用高效液相色谱法和酶联免疫法对茎尖、花序的植物激素指标进行测定分析.结果表明:(1)花椒开黄花的生理实质为雌蕊的缺失和雄蕊的出现.花芽分化期黄花株花芽发育时间比正常株早,且分化程度更高.初花期和盛花期黄花株表现为雄蕊异常发育、雌蕊缺失特征,正常株则为雌蕊发育;且在盛花期时,黄花株花芽表现出发育时间早、花芽数量过多的特征.花椒黄花株小花质量、小花数量和花叶质量比分别是正常株的1.61倍、2.86倍和7.65倍,黄花株新生叶质量降低23.3％,数量下降55.6％.(2)脱落酸(ABA)和水杨酸(SA)在黄花株和正常株的秋季茎尖及次年春季花序中的含量差异显著.黄花株秋季茎尖中ABA含量下降了45.6％,SA含量上升了1.18倍.(3)喷施三碘苯甲酸(TIBA)药物能够改善花椒开黄花现象.喷施100 mg?L?1 TIBA后,春季黄花株中的SA含量较正常株已无显著差异;喷施500 mg?L?1 TIBA后,黄花株中ABA和SA含量较正常株均无显著差异.综上结果显示ABA和SA在花椒开黄花中起到关键性作用.

The negative effect of ZnO nanoparticles (ZnO-NPs) on the biological removal of nitrate (NO3−) has received extensive attention, but the underlying mechanism is controversial. Additionally, there is no research on Fe2+ used to alleviate the cytotoxicity of NPs. In this paper, the effects of different doses of ZnO-NPs on the growth and NO3− removal of Pseudomonas tolaasii Y-11 were studied with or without Fe2+. The results showed that ZnO-NPs had a dose-dependent inhibition on the growth and NO3− removal of Pseudomonas tolaasii Y-11 and achieved cytotoxic effects through both the NPs themselves and the released Zn2+. The addition of Fe2+ changed the behavior of ZnO-NPs in an aqueous solution (inhibiting the release of toxic Zn2+ and promoting the aggregation of ZnO-NPs), thereby alleviating the poisonous effect of ZnO-NPs on the growth and nitrogen removal of P. tolaasii Y-11. This study provides a theoretical method for exploring the mitigation of the acute toxicity of ZnO-NPs to denitrifying microorganisms.

Resource utilization is an effective way to cope with the rapid increase of kitchen waste and excess sludge, and volatile fatty acids produced by anaerobic fermentation is an important way of recycling organic waste. However, the single substrate limits the efficient production of volatile fatty acids. In recent years, volatile fatty acids produced by anaerobic co-fermentation using different substrates has been widely studied and applied. In this paper, we analyze the characteristics of fermentation to produce acid using kitchen waste and excess sludge alone or mixture. Influences of environmental factors and microbial community structure on the type and yield of volatile fatty acids in the anaerobic fermentation system are discussed in detail. Moreover, we propose future research directions, to provide a reference for recycling kitchen waste and excess sludge.

Extensive use of CuO nanoparticles (CuO-NPs ) inevitably leads to their accumulation in wastewater and toxicity to microorganisms that effectively treat nitrogen pollution. Due to the effects of different mediums, the sources of CuO-NPs-induced toxicity to microorganisms and methods to mitigating the toxicity are still unclear. In this study, CuO-NPs were found to impact the nitrate reduction of Pseudomonas tolaasii Y-11 mainly through the action of NPs themselves while inhibiting the ammonium transformation of strain Y-11 through releasing Cu 2+ . As the content of CuO-NPs increased from 0 to 20 mg/L, the removal efficiency of NO 3 − and NH 4 + decreased from 42.29% and 29.83% to 2.05% and 2.33%, respectively. Exogenous Fe 2+ significantly promoted the aggregation of CuO-NPs, reduced the possibility of contact with bacteria, and slowed down the damage of CuO-NPs to strain Y-11. When 0.01 mol/L Fe 2+ was added to 0, 1, 5, 10 and 20 mg/L CuO-NPs treatment, the removal efficiencies of NO 3 - were 69.77%, 88.93%, 80.51%, 36.17% and 2.47%, respectively; the removal efficiencies of NH 4 + were 55.95%, 96.71%, 38.11%, 20.71% and 7.43%, respectively. This study provides a method for mitigating the toxicity of CuO-NPs on functional microorganisms.

为探究喷施铁肥对喀斯特地区石灰性土壤上蔬菜生长以及微生物多样性的影响,利用盆栽试验,清水作为对照（CK）,研究了0.05%硫酸亚铁（Y0）和有机铁肥（浓度梯度分别为0.05%、0.03%、0.025%、0.02%,记为Y1、Y2、Y3、Y4）对小白菜生物量、叶片抗氧化酶、土壤养分及微生物的影响,结果表明:0.05%硫酸亚铁对小白菜的地上部生物量具有抑制作用,比对照减少了14.16%,有机铁肥对小白菜的生物量表现出不同程度的促进,且Y3、Y4处理增加显著,分别比对照增加了54.26%和57.86%。与对照相比,有机铁肥不同程度增加了叶片抗氧化酶活性,其中超氧化物歧化酶（SOD）影响最大。除Y3、Y4处理外,其余处理均增加了丙二醛（MDA）含量。随有机铁肥浓度的减小,土壤碱解氮、有效磷及速效钾含量均呈下降趋势,而有机质呈上升趋势,土壤养分在Y4处理时有显著差异。Y4处理细菌、真菌及放线菌数量最高,分别为4.27、0.85和0.39 nmol·g -1 ,Y1处理最低,分别为1.18、0.20和0.12 nmol·g -1 。主成分分析表明,硫酸亚铁处理和有机铁肥处理之间土壤微生物群落结构有明显差异,Y0处理相对提高了革兰氏阴性菌（16∶1ω9c,18∶1ω7c）与放线菌（10Me17∶0,10Me18∶0）的丰度,Y3、Y4处理相对提高了革兰氏阳性菌（a17∶0,i18∶0）的丰度。通过对产量与多个因素的相关分析,结果表明小白菜产量与丙二醛呈显著负相关关系,与速效钾含量呈极显著负相关关系,而与土壤有机质含量呈显著正相关关系,但与不同微生物之间无显著相关性。综合比较,喷施0.02%有机铁肥对喀斯特地区小白菜产量及微生物多样性具有最佳效果,研究成果可为喀斯特岩溶地区生态农业发展提供参考。