Overlooked volcanic effect during transmission of antibiotic resistance genes induced by copper and zinc.

Adding heavy metals such as copper and zinc to animal feeds is common practice to promote growth, but meanwhile has side consequence of enhancing spread of antibiotic resistance genes (ARGs) in soil. This presents a global challenge to food security and human health. We in this study investigated the transmission of typical ARGs, i. e. ß-lactamase genes (ß-RGs), in dairy farm environments where dietary Cu and Zn were present in a wide range of concentration. The ß-RGs were demonstrated to be highly prevalent across environmental media, with a relative abundance of 94.55%, dominated by mechanisms of antibiotic deactivation (93.75%) and cellular protection (6.25%). More importantly, we first found the transmission of ARGs to be highly dependent on the overlooked volcanic effect, i. e. low-concentration Cu (12-22 mg/kg) and Zn (45-80 mg/kg) acted as micronutrients necessary for microbial growth but facilitated ARGs transfer, whereas higher-concentration Cu (22-39 mg/kg) and Zn (80-153 mg/kg) became toxic to microbial communities and gene expression patterns. Notably, the specific microbial phyla Proteobacteria (2.28-82.94%), Bacteroidetes (0.02-56.48%) and Actinobacteria (1.62-12.92%) exhibited resistance at low concentration of Cu and Zn, which enhanced the transmission of ß-RGs. However, this process was inhibited at higher concentration due to inactivation of microbes by Cu and Zn. The increase in resistance was first observed in class Gammaproteobacteria (2.02-88.51%) and Alphaproteobacteria (0.68-10.1%) with increased Cu and Zn concentration. This resulted in heightened transfer of ARGs by tnpA-07 (80.35%) due to protection of thicker cell membrane by chelation with Cu and Zn. This study not only offers mechanistic insights into the volcanic effect of dietary metals on dissemination of ARGs, but also has important implications for safe management of agricultural settings.

Machine Learning Models for Inverse Design of the Electrochemical Oxidation Process for Water Purification.

In this study, a machine learning (ML) framework is developed toward target-oriented inverse design of the electrochemical oxidation (EO) process for water purification. The XGBoost model exhibited the best performances for prediction of reaction rate (k) based on training the data set relevant to pollutant characteristics and reaction conditions, indicated by Rext2 of 0.84 and RMSEext of 0.79. Based on 315 data points collected from the literature, the current density, pollutant concentration, and gap energy (Egap) were identified to be the most impactful parameters available for the inverse design of the EO process. In particular, adding reaction conditions as model input features allowed provision of more available information and an increase in the sample size of the data set to improve the model accuracy. The feature importance analysis was performed for revealing the data pattern and feature interpretation by using Shapley additive explanations (SHAP). The ML-based inverse design for the EO process was generalized to a random case for tailoring the optimum conditions with phenol and 2,4-dichlorophenol (2,4-DCP) serving as model pollutants. The resulting predicted k values were close to the experimental k values by experimental verification, accounting for the relative error lower than 5%. This study provides a paradigm shift from conventional trial-and-error mode to data-driven mode for advancing research and development of the EO process by a time-saving, labor-effective, and environmentally friendly target-oriented strategy, which makes electrochemical water purification more efficient, more economic, and more sustainable in the context of global carbon peaking and carbon neutrality.

Distribution and transmission of ß-lactamase resistance genes in meal-to-milk chain on dairy farm.

Antibiotics have been widely used in animal husbandry, which leads to high risk of food-borne transfer of antibiotic resistance genes (ARGs). The present study investigated the distribution of ß-lactamase resistance genes (ß-RGs) on dairy farm in the Songnen Plain of western Heilongjiang Province, China, to provide mechanistic insights into food-borne transmission of ß-RGs through "meal-to-milk" chain under practically relevant circumstances. The results demonstrated that the abundance of ß-RGs (91%) was much higher than that of other ARGs in the livestock farms. The blaTEM exhibited the content as high as 94.55% among all ARGs, and higher than 98% blaTEM was detected in meal, water and milk sample. The metagenomic taxonomy analysis indicated that the blaTEM should be carried by tnpA-04 (7.04%) and tnpA-03 (1.48%) hosted in Pseudomonas genus (15.36%) and Pantoea (29.02%) genus. Both tnpA-04 and tnpA-03 in the milk sample were identified to be the key mobile genetic elements (MGEs) responsible for transferring blaTEM along the "meal-manure-soil-surface water-milk" chain. The ARGs transfer across ecological boundaries underscored the need to evaluate potential dissemination of high-risk Proteobacteria and Bacteroidetes carried by humans and animals. They were capable of producing expanded-spectrum ß-lactamases (ESBLs) and destroying commonly used antibiotics, leading to possible risk of food-borne horizontal transmission of ARGs. This study not only has important environmental implications for identifying the pathway for ARGs transfer, but also highlights the demand for appropriate policy toward safe regulation of dairy farm and husbandry products.

Flow electrochemical inactivation of waterborne bacterial endospores.

Waterborne pathogens have the risk of spreading waterborne diseases and even pandemics. Some Gram-positive bacteria can form endospores, the hardiest known life form that can withstand heat, radiation, and chemicals. Electrochemical inactivation may offer a promising solution, but is hindered by low inactivation efficiencies resulting from limitation of electrode/endospores interaction in terms of electrochemical reaction selectivity and mass transfer. Herein, these issues were addressed through modifying selectivity of active species formation using electroactive ceramic membrane with high oxygen evolution potential, improving mass transfer property by flow-through operation. In this way, inactivation (6.0-log) of Bacillus atrophaeus endospores was achieved. Theoretical and experimental results demonstrated synergistic inactivation to occur through fragmentation of coat via interfacial electron transfer and electro-produced transient radicals (•OH primarily, •Cl and Cl2•- secondarily), thereby increasing cell permeability to facilitate penetration of electro-produced persistent active chlorine for subsequent rupture of intracellular structures. Numbering-up electrode module strategy was proposed to scale up the system, achieving average 5.3-log inactivation of pathogenic Bacillus anthracis endospores for 30 days. This study demonstrates a proof-of-concept manner for effective inactivation of waterborne bacterial endospores, which may provide an appealing strategy for wide-range applications like water disinfection, bio-safety control and defense against biological warfare.

Sources, fates and treatment strategies of typical viruses in urban sewage collection/treatment systems: A review.

The ongoing coronavirus pandemic (COVID-19) throughout the world has severely threatened the global economy and public health. Due to receiving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a wide variety of sources (e.g., households, hospitals, slaughterhouses), urban sewage treatment systems are regarded as an important path for the transmission of waterborne viruses. This review presents a quantitative profile of the concentration distribution of typical viruses within wastewater collection systems and evaluates the influence of different characteristics of sewer systems on virus species and concentration. Then, the efficiencies and mechanisms of virus removal in the units of wastewater treatment plants (WWTPs) are summarized and compared, among which the inactivation efficiencies of typical viruses by typical disinfection approaches under varied operational conditions are elucidated. Subsequently, the occurrence and removal of viruses in treated effluent reuse and desalination, as well as that in sewage sludge treatment, are discussed. Potential dissemination of viruses is emphasized by occurrence via aerosolization from toilets, the collection system and WWTP aeration, which might have a vital role in the transmission and spread of viruses. Finally, the frequency and concentration of viruses in reclaimed water, the probability of infection are also reviewed for discussing the potential health risks.