Joint toxicity of tetracycline with copper(II) and cadmium(II) to Vibrio fischeri: effect of complexation reaction

Influence of surfactant molecular features on tetracycline transport in saturated porous media of varied surface heterogeneities

This study aims to understand how surfactants affect the mobility of tetracycline (TC), an antibiotic, through different aquifer media. Two anionic and cationic surfactants, sodium dodecylbenzene sulfonate (SDBS) and cetyltrimethyl ammonium bromide (CTAB), were used to study their influence on TC mobility through clean sand and humic acid (HA)-coated sand. HA coating inhibits TC mobility due to its strong interaction with TC. Both surfactants promoted TC mobility at pH 7.0 due to competitive deposition, steric effect, and increased hydrophilicity of TC. CTAB had a more substantial effect than SDBS, related to the surfactants' molecular properties. Each surfactant's promotion effects were greater in HA-coated sand than in quartz sand due to differences in surfactant retention. CTAB inhibited TC transport at pH 9.0 due to its significant hydrophobicity effect. Furthermore, in the presence of Ca2+, SDBS enhanced TC transport by forming deposited SDBS-Ca2+-TC complexes. On the other hand, CTAB increased TC mobility due to its inhibition of cation bridging between TC and porous media. The findings highlight surfactants' crucial role in influencing the environmental behaviors of tetracycline antibiotics in varied aquifers.

Four antibiotics and copper interactive effects on the growth and physiological characteristics of Hydrilla verticillata (L.f.) Royle

Co-pollution of antibiotics and heavy metal copper (Cu) is common in freshwater environments because of their wide use as antimicrobial agents, especially in aquaculture. However, the toxic effects of coexisting antibiotics and heavy metals on aquatic plants remain unclear. This study investigated the effect of four antibiotics (i.e., enrofloxacin, ENR; tetracycline, TC; sulfamethoxazole, SMX; erythromycin, ERY), Cu, and their mixture on the growth and physiological responses of Hydrilla verticillata (L.f.) Royle. Results showed that the four antibiotics exhibited toxic effects on the growth and physiological indicators of H. verticillata, and root elongation was the most sensitive endpoint of the phytotoxicity test. The median effect concentration (EC50) of root elongation indicated that TC (EC50 = 10.05 mg/L) has the highest level of growth toxicity, and the toxicity of ENR to aquatic plants was close to TC (EC50 = 10.44 mg/L), followed by SMX (EC50 = 20.08 mg/L). However, there was no significant toxic effect of 20 mg/L ERY on the root elongation. Hydrophobicity may be a key factor affecting the phytotoxicity of antibiotics. Moreover, antagonistic toxic effects were observed under ENR + Cu, TC + Cu, SMX + Cu, and ERY + Cu co-exposures at all the experimental concentrations (0.01-20 mg/L). Due to the concentrations of antibiotics in natural waters usually with ng/L levels, our results suggested that environmental antibiotic concentrations probably pose low ecological risk to aquatic plants and indicated the H. verticillata could be used as phytoremediation candidate to remove antibiotic or antibiotic-Cu pollutions in general nature water.

Application of the Aliivibrio fischeri bacterium bioassay for assessing single and mixture effects of antibiotics and copper

The Aliivibrio fischeri bioassay was successfully applied in order to evaluate the acute effect of sulfamethoxazole (SMX), ciprofloxacin (CIP), chlortetracycline (CTC) and copper (Cu), alone or in binary, ternary, and overall mixture. The toxicity results are reported in terms of both effective concentrations, which inhibited 50% of the bacterium bioluminescence (EC50%), and in Toxic Units (TUs). The TUs were compared with predicted values obtained using the Concentration Addition model (CA). Finally, the toxicity of water extracts from a soil contaminated by the three antibiotics (7 mg Kg-1 each) in the presence/absence of copper (30 mg Kg-1) was also evaluated. Copper was the most toxic chemical (EC50: 0.78 mg L-1), followed by CTC (EC50: 3.64 mg L-1), CIP (96 mg L-1) and SMX (196 mg L-1). Comparing the TU and CA values of the mixtures, additive effects were generally found. However, a synergic action was recorded in the case of the CIP+Cu co-presence and antagonistic effects in the case of CTC+Cu and the ternary mixture (containing each antibiotic at 0.7 mg L-1), were identified. Soil water extracts did not show any toxicity, demonstrating the buffering ability of the soil to immobilize these chemicals.

The presence of copper ions alters tetracycline removal pathway in aerobic granular sludge: Performance and mechanism

This study investigated the removal characteristics of tetracycline (TC) in the presence of copper ions (Cu2+) in aerobic granular sludge by analyzing the TC removal pathway, composition and functional group changes of extracellular polymeric substances (EPS), and microbial community structure. The TC removal pathway changed from cell biosorption to EPS biosorption, and the microbial degradation rate of TC was reduced by 21.37% in the presence of Cu2+. Cu2+ and TC induced enrichment of denitrifying bacteria and EPS-producing bacteria by regulating the expression of signaling molecules and amino acid synthesis genes to increase the content of EPS and -NH2 groups in EPS. Although Cu2+ reduced the content of acidic hydroxyl functional groups (AHFG) in EPS, an increase in TC concentration stimulated the secretion of more AHFG and -NH2 groups in EPS. The long-term presence of TC presence of the relative abundances of Thauera, Flavobacterium and Rhodobacter and improved the removal efficiency.

The Impact of Copper Ions on the Activity of Antibiotic Drugs

Copper (Cu) is an essential trace metal and its concentration in body plasma is tightly regulated. An increase in Cu concentration in body fluids is observed in numerous pathological conditions, including infections caused by microorganisms. Evidence shows that Cu ions can impact the activity of antibiotics by increasing efficiency or diminishing/neutralizing antibiotic activity, forming complexes which may lead to antibiotic structure degradation. Herein, we represent the evidence available on Cu-antibiotic interactions and their possible impact on antimicrobial therapy efficiency. So far, in vitro studies described interactions between Cu ions and the majority of antibiotics in clinical use: penicillins, cephalosporins, carbapenems, macrolides, aminoglycosides, tetracyclines, fluoroquinolones, isoniazid, metronidazole. In vitro-described degradation or lower antimicrobial activity of amoxicillin, ampicillin, cefaclor, ceftriaxone, and meropenem in the presence of Cu ions suggest caution when using prescribed antibiotics in patients with altered Cu levels. On the other hand, several Cu-dependent compounds with antibacterial activity including the drug-resistant bacteria were discovered, such as thiosemicarbazones, disulfiram, dithiocarbamates, 8-hydroxiquinoline, phenanthrolines, pyrithione. Having in mind that the development of new antibiotics is already marked as inadequate and does not meet global needs, the potential of Cu-antibiotic interactions to change the efficiency of antimicrobial therapy requires further investigation.

Accumulation, transportation, and distribution of tetracycline and cadmium in rice

Co-exposure to heavy metal and antibiotic pollution might result in complexation and synergistic interactions, affecting rice growth and further exacerbating pollutant enrichment. Therefore, our study sought to clarify the influence of different Tetracycline (TC) and Cadmium(Cd) concentration ratios (both alone and combined) on rice growth, pollutant accumulation, and transportation during the tillering stage in hydroponic system. Surprisingly, our findings indicated that the interaction between TC and Cd could alleviate the toxic effects of TC/Cd on aerial rice structures and decrease pollutant burdens during root elongation. In contrast, TC and Cd synergistically promoted the accumulation of TC/Cd in rice roots. However, their interaction increased the accumulation of TC in roots while decreasing the accumulation of Cd when the toxicant doses increased. The strong affinity of rice to Cd promoted its upward transport from the roots, whereas the toxic effects of TC reduced TC transport. Therefore, the combined toxicity of the two pollutants inhibited their upward transport. Additionally, a low concentration of TC promoted the accumulation of Cd in rice mainly in the root tip. Furthermore, a certain dose of TC promoted the upward migration of Cd from the root tip. Laser ablation-inductively coupled plasma mass spectrometry demonstrated that Cd mainly accumulated in the epidermis and stele of the root, whereas Fe mainly accumulated in the epidermis, which inhibited the absorption and accumulation of Cd by the rice roots through the generation of a Fe plaque. Our findings thus provide insights into the effects of TC and Cd co-exposure on rice growth.

Simultaneous removal of tetracycline and sulfamethoxazole by laccase-mediated oxidation and ferrate(VI) oxidation: the impact of mediators and metal ions

This study explores the impact of mediators and metal ions of laccase-mediated oxidation and ferrate(VI) oxidation for the simultaneous removal of tetracycline antibiotics (TCs) and sulfonamide antibiotics (SAs) and to effectively remove their antimicrobial activity. The results showed that the antimicrobial activity of tetracycline against Bacillus altitudinis and Escherichia coli was significantly reduced, and the antimicrobial activity of sulfamethoxazole against B. altitudinis disappeared completely after treatment with the laccase-ABTS system. The combination of 6.0 U/mL of laccase and 0.2 mmol/L of ABTS removed 100% of 20.0 mg/L of tetracycline after 1.0 min at pH 6.0 and 25.0 °C, whereas the removal ratio of 20.0 mg/L of sulfamethoxazole was only 6.7%. The Al3+ and Cu2+ ions promoted the oxidation, and the Mn2+ ion decelerated the oxidation of tetracycline and sulfamethoxazole by the laccase-mediator systems. In contrast, the antimicrobial activity of tetracycline against B. altitudinis and E. coli was shown to be significantly reduced, and the sulfamethoxazole still retained high antimicrobial activity against B. altitudinis after treatment with Fe(VI) oxidation. The removal ratio of 20.0 mg/L of tetracycline was 100% after 1.0 min of treatment with 982.0 mg/L of K2FeO4 at pH 6.0 and 25.0 °C, whereas the removal ratio of 20.0 mg/L of sulfamethoxazole was only 49.5%. The Al3+, Cu2+, and Mn2+ ions both decelerated the oxidation of tetracycline and sulfamethoxazole by Fe(VI) oxidation. In general, the combination of the laccase-ABTS system and Fe(VI) was proposed for the simultaneous treatment of TCs and SAs in wastewater and to effectively remove their antimicrobial activity.

Individual and combined contamination of oxytetracycline and cadmium inhibited nitrification by inhibiting ammonia oxidizers

Introduction

The large-scale development of animal husbandry and industrialization lead to more and more serious co-contamination from heavy metals and antibiotics in soils. Ecotoxic effects of residues from antibiotics and heavy metals are of increasing concern.

Materials and Methods

In this study, oxytetracycline (OTC) and cadmium (Cd) were selected as target pollutants to evaluate the individual and combined effects on nitrification process using four different soil types sampled from North to South China through a 56-day incubation experiment.

Results and Discussion

The results demonstrated that the contaminations of OTC and Cd, especially combined pollution had significant inhibitory effects on net nitrification rates (NNRs) as well as on AOA and AOB abundance. The toxic effects of contaminants were greatly enhanced with increasing OTC concentration. AOB was more sensitive than AOA to exogenous contaminants. And the interaction effects of OTC and Cd on ammonia oxidizers were mainly antagonistic. Furthermore, Cd contaminant (with or without OTC) had indirect effects on nitrification activity via inhibiting mineral N and AOA/AOB, while OTC alone indirectly inhibited nitrification activity by inhibiting ammonia oxidizers. The results could provide theoretical foundation for exploring the eco-environmental risks of antibiotics and heavy metals, as well as their toxic effects on nitrification processes.

Effects of heavy metals and antibiotics on performances and mechanisms of anaerobic digestion

Anaerobic digestion (AD) is an efficacious technology to recover energy from organic wastes/wastewater, while the efficiency of AD could be limited by metals and antibiotics in substrates. It is of great significance to deeply understand the interaction mechanisms of metals and antibiotics with anaerobic microorganisms, as well as the combined effects of metals and antibiotics, which will help us break the inherent dysfunction of AD system and promote the efficient operation of AD. Therefore, this paper reviews the effects of metals, antibiotics and their combinations on AD performance, as well as the combined effects and interactional mechanisms of metals and antibiotics with anaerobic microorganisms. In addition, control strategies and future research needs are proposed. This review provides valuable information for the enhancement strategies and engineering applications of AD for organic wastes/wastewater containing metals and antibiotics.

Enhanced degradation of tetracycline over FeS-based Fenton-like process: Autocatalytic decomposition of H2O2 and reduction of Fe(III)

This study constructed a FeS-based Fenton-like process to explore the degradation of TTC in the presence of copper ions. The acidic condition of pH 3 was more favorable to the H₂O₂ decomposition and TTC degradation, and it was slightly enhanced by Cu(II). The production of •OH from H₂O₂ was revealed through radical scavenging and benzoic acid probe experiments, and the ratio of H₂O₂ decomposition to •OH production was about 1-1.5, which is comparatively consistent with the theoretical ratio. FeS-based Fenton process was proved to be a homogenous system, the slow release of Fe(II) source and the autocatalytic cycle of Fe(III) to Fe(II) resulting from the reductive species of TTC and dissolved S(-II) improved the production of •OH and the degradation of TTC, which was proved by comparing TTC degradation, TOC removal, H₂O₂ decomposition and Fe(II) concentration with different iron sources (FeS, Fe(II) and Fe(III)) and external addition of dissolved S(-II). The possible degradation pathways of TTC were subsequently inferred according to the detected products by LC-MS. Understanding these autocatalytic processes is essential to reveal the transformation of redox-active substances in environments and may have potential significance in applying FeS-based Fenton-like process for the treatment of wastewater containing reductive organic matters.

The dissimilarity of antibiotic and quorum sensing inhibitor on activated sludge nitrification system: Microbial communities and antibiotic resistance genes

Effects of antibiotics (azithromycin, AZM, 1-40 mg/L) and quorum sensing inhibitor (QSI, 2(5H)-furanone, 1-40 mg/L) combined pollution with environmental concentration of copper on bacterial/archaeal community and antibiotic resistance genes (ARGs) in activated sludge system were explored. QSI inhibited nitrification more obviously than AZM. AZM and QSI were synergistic inhibitions on bacterial diversity, and AZM inhibited bacterial compositions more than QSI. While, QSI had more impacts on archaeal diversity/compositions. Less interactions among bacteria and archaea communities with Aquimonas as keystone genus. Functional differences in bacteria/archaea communities were little, and AZM had more effects on metabolism. AZM mainly affected nitrifying bacteria (Candidatus Nitrospira nitrificans and Nitrosomonas). Specific denitrifying bacteria were enriched by AZM (Brevundimonas, 1.76-31.69%) and QSI (Comamonas, 0.61-9.61%), respectively. AZM enriched ARGs more easily than QSI and they were antagonistic to proliferation of ARGs. Bacteria were main hosts of ARGs (macrolide-lincosamide-streptogramin B, other/efflux, etc.) and archaea (Methanosphaerula, Methanolobus) carried multiple ARGs.

Combined effect of tetracycline and copper ion on catalase activity of microorganisms during the biological phosphorus removal

Microbial catalase is a key enzyme that affects the activities of microorganisms, and the catalase activity is affected by pollutants in wastewater. However, the effects of mixed pollutants on catalase activity are rather complex. To reveal the effect of the mixed pollutants on catalase activity of microorganisms, the present study investigated tetracycline and copper ion as pollutants during the biological phosphorus removal. Three concentration ratios of tetracycline and copper ion and 27 different concentration gradients were designed through the direct equipartition ray and the dilution factor method. The effects of mixed pollutants on the catalase activity of microorganisms were analyzed by the nonlinear regression equation and concentration-addition model. The results showed that, with the increase of actuation duration and the pollutant concentration, the inhibitory effects on the catalase activity of microorganisms obviously increased, which indicated that the inhibitory effects are concentration-dependent and time-dependent. The concentration-addition model suggested that when the ratio was 0.297, the combined effect of mixed pollutants on the activity of microbial catalase was mainly antagonism. When the ratio is 0.894, the combined effect was mainly additivity. When the ratio was 2.676, the combined effect transformed from synergism to additivity and antagonism. The study of the combined effects of tetracycline and copper ion on the catalase activity is helpful to further study their ecotoxicological mechanisms in wastewater treatment.

Impacts of combined pollution under gradient increasing and gradient decreasing exposure modes on activated sludge: Microbial communities and antibiotic resistance genes

The responses of microbial communities and antibiotic resistance genes (ARGs) to azithromycin and copper combined pollution under gradient increasing (from 0.5 to 10 mg/L) and decreasing exposure (from 10 to 0.5 mg/L) modes were investigated. Nitrification was inhibited more obviously under gradient increasing exposure mode. Responses of archaeal community and function structure were more obvious than bacteria under both exposure modes. The dominant bacterial and archaeal compositions (Hyphomicrobium, Euryarchaeota, etc.) were affected by two exposure modes, except some rare archaea (Methanoregula and Methanosarcina). There were more positive correlations between bacteria and archaea, and Nitrospira was keystone genus. Ammonia-oxidizing archaea (0.37-3.06%) and complete ammonia oxidizers (Nitrospira_ENR4) were enriched, and Nitrososphaera_viennensis was closely related to denitrifying genes (napA/B, nosZ, etc.). 50 ARG subtypes were detected and specific ARG subtypes (aac, ImrA, etc.) proliferated in two exposure modes. Bacteria and archaea were common hosts for 24 ARGs and contributed to their shifts.

Pseudo toxicity abatement effect of norfloxacin and copper combined exposure on Caenorhabditis elegans

The coexistence of antibiotics and heavy metals may result in complex ecotoxicological effects on living organisms. In this work, the combined toxic effects of norfloxacin (NOR) and copper (Cu) on Caenorhabditis elegans (C. elegans) were investigated due to the highly possible co-pollution tendency. The results indicated that locomotion behaviors (frequency of head thrash and body bend) of C. elegans were more sensitive as the exposure time of NOR or Cu prolonged. Meanwhile, the physiological indexes (locomotion behaviors, body length) of C. elegans were more sensitive to the combined pollution that with lower Cu dosage (0.0125 μM), in prolonged exposure experiments. In addition, the toxic effects of NOR-Cu on physiological indexes of C. elegans seemed to be alleviated during prolonged exposure when Cu was 1.25 μM. Similarly, the ROS production and apoptosis level almost unchanged with the addition of NOR compared with Cu (1.25 μM) exposure groups, but both significantly higher than the control groups. Furthermore, compared with Cu (0.0125 μM and 1.25 μM) exposure experiments, the addition of NOR had resulted in the genetic expression decrease of hsp-16.1, hsp-16.2, hsp-16.48, and the oxidative stress in C. elegans seems to be alleviated. However, the significantly decreased of ape-1 and sod-3 expression indicated the disruption of ROS defense mechanism. The irregular change in ace-1 and ace-2 gene expressions in NOR-Cu (0.0125 μM) would result in the locomotion behaviors disorders of C. elegans, and this also explains why C. elegans are more sensitive to the combination of NOR and lower concentration of Cu.

Bacterial bioluminescence assay for bioanalysis and bioimaging

Bioluminescence occurs through a chemical reaction in organisms that spontaneously produce light. Luminescent bacteria are unique among bioluminescent organisms. Their bioluminescence intensity is an indicator of their metabolic activity, which can directly reflect the influence of environmental factors on cell viability. Moreover, the whole bioluminescence process is totally gene encoded without the addition of extra substrates. As a result, bacterial bioluminescence has been a powerful tool for whole-cell biosensors and bio-reporters in bioanalysis and bioimaging. This review aims to cover the applications of wild-type and recombinant luminescent bacteria to detect the toxicity of environmental pollutants and biological molecules. The bacterial bioluminescence analytical assay has characteristics such as high sensitivity, short-term detection, and easy operation. Meanwhile, due to the development of gene engineering and optical technology, bacterial luciferase as a reporter protein has been successfully expressed in prokaryotic and eukaryotic cells, tissues, and organs of animals. The major applications for bacterial luciferase-based bioluminescence imaging, such as infectious diseases, cancer therapy, and stem cell tracing, are discussed in this review.

Toxicologic effect and transcriptome analysis for short-term orally dosed enrofloxacin combined with two veterinary antimicrobials on rat liver

Presently, toxicological assessment of multiple veterinary antimicrobials has not been performed on mammals. In this study, we assessed the short-term toxicity of enrofloxacin (E) combined with colistin (C) and quinocetone (Q). Young male rats were orally dosed drug mixtures and single drugs in 14 consecutive days, each at the dose of 20, 80, and 400 mg/(kg·BW) for environmental toxicologic study. The results showed that at the high dose treatment, the combination of E + C+Q significantly decreased body intake, lymphocytes count on rats; significantly increased the values of Alanine aminotransferase (ALT), Glutamic oxaloacetic transaminase (AST) and, cholinesterase (CHE); it also got the severest histopathological changes, where sinusoidal congestion and a large number of black particles in sinusoids were observed. This means E + C+Q in the high dose groups was able to cause significant damage to the liver. Other combinations or doses did not induce significant liver damage. Transcriptome analysis was then performed on rats in high dose group for further research. For E + C and E + Q, an amount of 375 and 480 differently expressed genes were filtered out, revealing their possible underlying effect on genomes. For E + C+Q, a weighted gene co-expression network analysis was performed and 96 hub genes were identified to reveal the specific effect induced by this combination. This study indicates that joint toxicity should be taken into consideration when involving the risk assessment of these antimicrobials.

Tetracyclines in the environment: An overview on the occurrence, fate, toxicity, detection, removal methods, and sludge management

Tetracyclines (TCs) are a group of broad-spectrum antibiotics having vast human, veterinary, and aquaculture applications. The continuous release of TCs residues into the environment and the inadequate removal through the conventional treatment systems result in its prevalent occurrence in soil, surface water, groundwater, and even in drinking water. As aqueous TCs contamination is the tip of the iceberg, and TCs possess good sorption capacity towards soil, sediments, sludge, and manure, it is insufficient to rely on the sorptive removal in the conventional water treatment plants. The severity of the TCs contamination is evident from the emergence of TCs resistance in a wide variety of microorganisms. This paper reviews the recent research on the TCs occurrence in the environmental matrices, fate in natural systems, toxic effects, and the removal methods. The high performance liquid chromatography (HPLC) determination of TCs in environmental samples and the associated technology developments are analyzed. The benefits and limitations of biochemical and physicochemical removal processes are also discussed. This work draws attention to the inevitability of proper TC sludge management. This paper also gives insight into the limitations of TCs related research and the future scope of research in environmental contamination by TCs residues.

Advances in Understanding of the Copper Homeostasis in Pseudomonas aeruginosa

Thirty-five thousand people die as a result of more than 2.8 million antibiotic-resistant infections in the United States of America per year. Pseudomonas aeruginosa (P. aeruginosa) is classified a serious threat, the second-highest threat category of the U.S. Department of Health and Human Services. Among others, the World Health Organization (WHO) encourages the discovery and development of novel antibiotic classes with new targets and mechanisms of action without cross-resistance to existing classes. To find potential new target sites in pathogenic bacteria, such as P. aeruginosa, it is inevitable to fully understand the molecular mechanism of homeostasis, metabolism, regulation, growth, and resistances thereof. P. aeruginosa maintains a sophisticated copper defense cascade comprising three stages, resembling those of public safety organizations. These stages include copper scavenging, first responder, and second responder. Similar mechanisms are found in numerous pathogens. Here we compare the copper-dependent transcription regulators cueR and copRS of Escherichia coli (E. coli) and P. aeruginosa. Further, phylogenetic analysis and structural modelling of mexPQ-opmE reveal that this efflux pump is unlikely to be involved in the copper export of P. aeruginosa. Altogether, we present current understandings of the copper homeostasis in P. aeruginosa and potential new target sites for antimicrobial agents or a combinatorial drug regimen in the fight against multidrug resistant pathogens.

A comparison study of test organism species and methodologies for combined toxicity assay of copper ions and zinc ions

The general toxicity assays for evaluating the risk of aquatic environment were commonly based on single-species test organism models. Thus, the lack and conflict of the different responses among species had hindered researchers to assess the real toxicity of a target toxicant. Therefore, the difference between the test species and their corresponding methodologies was investigated in this work and three species, Escherichia coli, Saccharomyces cerevisiae and Misgurnus anguillicaudatus (a fish), were chosen as the test organism for typical prokaryotes, eukaryotes, and vertebrates, respectively. More specifically, we investigated (i) the individual and combined toxicity of Cu²⁺ and Zn²⁺ by the three test organisms; (ii) the different evaluation manners for the test organisms, including IC₅₀ and toxic unit (TU) model for microorganisms by respiratory toxicity assay and enzyme-substrate assay, while survival time for fish; and (iii) the states of test organism, including suspended and immobilized states for microorganisms. The combined effects, including synergistic (Vt < Vp), antagonistic (Vt > Vp) and additive effects for the three species, were complex as that they were usually dose-dependent and could be changed by the different evaluation manners. The present work was useful for enriching of the associated theory and the insights from this work could open the way for further practical risk assessments.

UVC- and UVC/H2O2-Driven nonribosomal peptide antibiotics degradation: application to zinc bacitracin as a complex emerging contaminant

Zinc bacitracin (Zn-Bc) belongs to the group of nonribosomal peptide antibiotics (NRPA), comprising a mixture of non-biodegradable congeners characterized by complex structures containing cyclic, polycyclic, and branched chains. However, reports on the use of AOPs for the degradation of NRPA are non-existent. In this context, the present work investigated the photodegradation of Zn-Bc in aqueous solution by direct photolysis and the UVC/H₂O₂ process. The effects of the specific UVC photon emission rate and initial H₂O₂ concentration were studied following a Doehlert-design response surface approach. The results showed that all congeners photolyzed at the highest UVC doses in the absence of hydrogen peroxide, with a calculated quantum yield of 0.0141 mol Zn-Bc mol photons^-1. However, no TOC removal was observed after 120 minutes of irradiation, suggesting the disruption of the peptide bonds in the antibiotic molecules without significant changes in the amino acid residues. The addition of H₂O₂ substantially accelerated Zn-Bc photodegradation, resulting in a remarkable removal of up to 71% of TOC. Most importantly, the antimicrobial activity against Staphylococcus aureus could be completely removed by both treatments. These findings point out that the UVC/H₂O₂ process can be straightly engineered for the treatment of metalloantibiotics-containing wastewater in pharmaceutical facilities.

Evaluating responses of nitrification and denitrification to the co-selective pressure of divalent zinc and tetracycline based on resistance genes changes

The responses of nitrification and denitrification to the divalent zinc (Zn(II)) and tetracycline (TC) co-selective pressure were evaluated in a sequencing batch reactor (SBR). The removal rates of organics and nitrogen, nitrifying and denitrifying enzymatic activity, and microbial diversity and richness at the Zn(II) and TC co-selective pressure were higher than those at the alone Zn(II) selective pressure, while were lower than those at the individual TC selective pressure. The Zn(II) and TC co-selective pressure induced the TC resistance genes abundance increase and the Zn(II) resistance genes levels decrease, and enhanced bacterial enzymatic modification resistance to TC and bacterial outer membrane resistance to Zn(II). The network analysis showed that the genera Nitrospira and Nitrosomonas of nitrifiers and the genera Ferruginibacter, Dechloromonas, Acidovorax, Rhodobacter, Thauera, Cloacibacterium, Zoogloea and Flavobacterium of denitrifiers were the potential hosts of antibiotics resistance genes (ARGs) and/or heavy metals resistance genes (HMRGs).

Mathematical Modeling Approaches for Assessing the Joint Toxicity of Chemical Mixtures Based on Luminescent Bacteria: A Systematic Review

Developments in industrial applications inevitably accelerate the discharge of enormous substances into the environment, whereas multi-component mixtures commonly cause joint toxicity which is distinct from the simple sum of independent effect. Thus, ecotoxicological assessment, by luminescent bioassays has recently brought increasing attention to overcome the environmental risks. Based on the above viewpoint, this review included a brief introduction to the occurrence and characteristics of toxic bioassay based on the luminescent bacteria. In order to assess the environmental risk of mixtures, a series of models for the prediction of the joint effect of multi-component mixtures have been summarized and discussed in-depth. Among them, Quantitative Structure-Activity Relationship (QSAR) method which was widely applied in silico has been described in detail. Furthermore, the reported potential mechanisms of joint toxicity on the luminescent bacteria were also overviewed, including the Trojan-horse type mechanism, funnel hypothesis, and fishing hypothesis. The future perspectives toward the development and application of toxicity assessment based on luminescent bacteria were proposed.

Oxidation of tetracycline and oxytetracycline for the photo-Fenton process: Their transformation products and toxicity assessment

Advanced oxidation processes have gained significant attention for treating tetracycline (TC) and oxytetracycline (OTC), however, their oxidation using the photo-Fenton process has not been sufficiently studied. Although degradations of TC and OTC were enhanced by increasing H₂O₂ and Fe²⁺ within the ranges investigated (H₂O₂ = 20-50 mg/L and Fe = 1-10 mg/L) under UV irradiation, further experiments for the photo-Fenton process were conducted with 20 mg/L of H₂O₂ and 5 mg/L of Fe²⁺ to balance efficiency and cost. The photo-Fenton process (UV/H₂O₂/Fe²⁺) was shown to be more effective to remove TC and OTC than H₂O₂, ultraviolet (UV), and UV/H₂O₂ at the same doses of oxidants. Inorganic anions and cations were shown to inhibit the degradation of TC and OTC during the photo-Fenton process, in the following order: HPO₄^2- > HCO₃^- ≫ SO₄^2- > Cl^- and Cu²⁺ ≫ Ca²⁺ > Na⁺. The TC and OTC degradation are generally improved by increasing pH, which is opposite to the k_pCBA,obs values, caused by increasing the deprotonation degree of TC and OTC. Four and nine transformation products of TC and OTC, respectively, were detected over the treatment period. Among the transformation products, m/z 443.14 (C₂₂H₂₂N₂O₈) formed during TC degradation, and m/z 433.16 (C₂₀H₂₀N₂O₉) and m/z 415.15 (C₂₀H₁₈N₂O₈) formed during OTC degradation, were reported for the first time. Vibrio fischeri toxicity assessment indicated that the inhibition ratio was decreased with a decreasing TC concentration, while, OTC transformation lead to higher toxicity. The product (m/z 477.15b) was determined to be the compound causing toxicity during degradation of OTC by using the quantitative structure activity relationship (QSAR). This toxic transformation product caused higher inhibition ratios than its parental compound (OTC), but its further oxidization resulted in decreasing the inhibition ratios.

Calcium Ions Turn on the Fluorescence of Oxytetracycline for Sensitive and Selective Detection

Herein, we report an interesting finding about the new application of oxytetracycline (OTC), as a fluorescent probe for the detection of calcium ion (Ca²⁺), which proved that it can offer an expeditious, highly sensitive, and selective detection method for Ca²⁺. Upon the addition of Ca²⁺, the fluorescence of OTC could be significantly enhanced with rapid response and high sensitivity, and achieved a good limit of detection as low as 125 nM in aqueous solution. The complex formed via Ca²⁺ coordinating to the hydroxyl group of OTC contributes to the fluorescence enhancement, which has been proved by several characterization methods including UV-vis analysis, binding constant determination, and fluorescence titration. The method avoided complexity for EDTA measurement of Ca²⁺ in running water as proposed previously. Taking advantage of good availability, stability and operability, the OTC was further successfully applied to the detection of Ca²⁺ in a real environment. Graphical Abstract.

Separate and joint eco-toxicological effects of sulfadimidine and copper on soil microbial biomasses and ammoxidation microorganisms abundances

Heavy metals and antibiotics residues in agricultural soils are attracting more and more attention. A laboratory study was conducted to evaluate the single and combined effects of sulfadimidine (SM2) (0.05, 0.20, 0.80 mmol/kg) and copper (Cu) (1.60 mmol/kg) on soil microbial biomasses and ammoxidation microorganisms abundances after 7, 14, 21 and 28 days. The results demonstrated that the single and combined contaminations had a significant and persistent inhibitory effect on soil bacteria, fungi and actinomycetes populations and amoA gene copies of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) (Except SM2 0.05 and 0.20 mmol/kg on 7 and 14 d and SM2 0.05 mmol/kg on 21 d led to a stimulatory effect on fungi and AOA-amoA gene, respectively). With higher dosage and longer exposure time, the toxic effect of single and combined contaminants on soil bacteria, fungi and actinomycetes as well as on the amoA gene of AOA and AOB was greatly reinforced. Combined contaminants produced more toxicity than the chemicals were used alone. Overall, the interaction effects of SM2 and Cu on bacteria (on 14, 21 and 28 d), fungi and AOA-amoA were mainly synergism, in contrast, on actinomycetes (on 14, 21 and 28 d) and AOB-amoA were mainly antagonism. The order of the toxic effects of the single Cu and combined contaminants on microbial activity was: bacteria > actinomycetes > fungi. Furthermore, AOB-amoA was more sensitive to both contaminants toxicity than AOA-amoA, while AOA-amoA gene copies were greater than AOB-amoA gene copies about one order of magnitude.

Effects of divalent metal cations and inorganic anions on the transport of tetracycline in saturated porous media: column experiments and numerical simulations

Tetracycline is one of the most commonly used antibiotics in the world. Eventually, large amounts of this contaminant will enter into the subsurface environment, where a variety of ions exist. In this study, the effects of divalent metal cations (Mg2+, Ca2+, Pb2+ and Cu2+) and inorganic anions (Cl-, NO3-, SO42- and H2PO4-) on the transport of tetracycline in saturated porous media were investigated. Both batch and column experiments were conducted to determine the interactions between tetracycline and sand. Batch sorption experimental results showed that the presence of divalent metal cations could increase the sorption of tetracycline onto sand due to the cation-bridging mechanism. When Na+ was the counterion in the background solution, anions caused a significant decrease in tetracycline sorption owing to the occupation of some adsorption sites by anions and the decrease of electrostatic attraction. Column experiments indicated that the inhibition effects of divalent cations followed the order of Cu2+ > Pb2+ > Ca2+ ≈ Mg2+; the regular pattern might be related to their different complexing strengths. The presence of inorganic anions enhanced the mobility of tetracycline following the order of H2PO4- > SO42- > NO3- > Cl-. Transport-enhancement effects of anions were ascribed to competition between inorganic anions and tetracycline for deposition sites on sand surfaces. However, when Ca2+ was the counterion, the differences in the breakthrough curve of tetracycline among three inorganic anions (i.e., SO42-, NO3- and Cl-) were very small. In this case, the transport-inhibiting effects of anions could be counterbalanced by the transport-enhancement effects of the cation-bridging effect. Also, the two-site nonequilibrium transport model was applied to analyze the transport data. Findings from this study improve our understanding of the transport of tetracycline in saturated aquifer materials.

Development and evaluation of diffusive gradients in thin films based on nano-sized zinc oxide particles for the in situ sampling of tetracyclines in pig breeding wastewater

The pollution of antibiotics, including tetracyclines (TCs), in aquatic environments has become an issue of concern in recent years. Herein, an in situ sampling of TCs in pig breeding wastewater that utilizes the technique of diffusive gradients in thin films (DGT), based on commercial nanosized ZnO (nanoZnO) particles as the potential effective binding agent and a polyethersulfone (PES) membrane as the diffusion layer, was developed. The diffusion coefficients of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) in a PES membrane at 25 °C were (1.37 ± 0.06) × 10^-6 cm² s^-1, (1.29 ± 0.05) × 10^-6 cm² s^-1 and (1.94 ± 0.07) × 10^-6 cm² s^-1, respectively. The results showed that the adsorption capacities of a gel disc containing 2.5 g L^-1 of nanoZnO particles were as high as 3.93 ± 0.20 mg disc^-1 for TC, 3.21 ± 0.20 mg disc^-1 for OTC and 4.62 ± 0.22 mg disc^-1 for CTC. Both a solution pH in the range of 5-9 and an ionic strength (as pNaCl) in the range of 1-3 had an insignificant influence on the TCs uptake by nanoZnO-DGT samplers. There was no significant influence of fulvic acid or tannic acid on the TC uptake by nanoZnO-DGT samplers at the tested mass ratios. For all spiked freshwater samples, there was no notable interference of matrices on the performance of the nanoZnO-DGT samplers, suggesting that the nanoZnO-DGT samplers yielded satisfactory results for the uptake of TCs at concentrations existing in the spiked freshwater samples. Field deployment of the nanoZnO-DGT samplers in pig breeding wastewater also exhibited excellent precision and accuracy, indicating that the nanoZnO-DGT samplers could be used as a promising method for the in situ sampling of TC antibiotics in aquatic environments.

Effects of sub-lethal concentrations of copper ammonium acetate, pyrethrins and atrazine on the response of Escherichia coli to antibiotics

Background: Antibiotic resistance in human and animal pathogens is mainly the outcome of human use of antibiotics. However, bacteria are also exposed to thousands of other antimicrobial agents. Increasingly those exposures are being investigated as co-selective agents behind the rapid rise and spread of resistance in bacterial pathogens of people and our domesticated animals. Methods: We measured the sub-lethal effects on antibiotic tolerance of the human pathogen/commensal Escherichia coli caused by exposure to three common biocide formulations based on either copper, pyrethrins, or atrazine as active ingredients. The influence of the efflux pump AcrAB-TolC was investigated using deletion strains, and the persistence of observed effects was determined. Results: Some effects were seen for all biocides, but the largest effects were observed with copper in combination with the antibiotic tetracycline. The effect was caused by both the induction of the adaptive efflux system and by chelation of the antibiotic by copper. Finally, persistence of the adaptive response was measured and found to persist for about two generations. Conclusions: Through a combination of microbe-chemical and chemical-chemical interactions, humanity may be creating micro-environments in which resistance evolution is accelerated.

Monitoring Aquaculture Water Quality: Design of an Early Warning Sensor with Aliivibrio fischeri and Predictive Models

A novel toxicity-warning sensor for water quality monitoring in recirculating aquaculture systems (RAS) is presented. The design of the sensor system mainly comprises a whole-cell biosensor. Aliivibrio fischeri, a luminescent bacterium widely used in toxicity analysis, was tested for a mixture of known fish-health stressors, namely nitrite, un-ionized ammonia, copper, aluminum and zinc. Two toxicity predictive models were constructed. Correlation, root mean squared error, relative error and toxic behavior were analyzed. The linear concentration addition (LCA) model was found suitable to ally with a machine learning algorithm for prediction of toxic events, thanks to additive behavior near the limit concentrations for these stressors, with a root-mean-squared error (RMSE) of 0.0623, and a mean absolute error of 4%. The model was proved to have a smaller relative deviation than other methods described in the literature. Moreover, the design of a novel microfluidic chip for toxicity testing is also proposed, which is to be integrated in a fluidic system that functions as a bypass of the RAS tank to enable near-real time monitoring. This chip was tested with simulated samples of RAS water spiked with zinc, with an EC50 of 6,46E-7 M. Future work will be extended to the analysis of other stressors with the novel chip.

Vibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment: A review

Vibrio fischeri bioluminescence inhibition bioassay (VFBIA) has been widely applied for the monitoring of toxicity on account of multiple advantages encompassing shorter test duration, sensitive, cost-effective and ease of operation. Moreover, this bioassay found to be equally applicable to all types of matrices (organic & inorganic compounds, metals, wastewater, river water, sewage sludge, landfill leachate, herbicides, treated wastewater etc.) for toxicity monitoring. This review highlights the apparent significance of Vibrio fischeri bioluminescence inhibition assay for ecotoxicological screening and evaluation of diverse chemical substances toxicity profile. The biochemical and genetic basis of the bioluminescence assay and its regulatory mechanism have been concisely discussed. The basic test protocol with ongoing improvements, widespread applications, typical advantages and probable limitations of the assay have been overviewed. The sensitivity of VFBIA and toxicity bioassays has also been compared.

Toxic effects of nanomaterial-adsorbed cadmium on Daphnia magna

Chemical immobilization technologies involving the use of chemical absorbents such as nanomaterials have been recommended for the remediation of Cd-contaminated water and soil. The impact of nanomaterials or nanomaterials coexisting with other contaminants on aquatic organisms has been reported, but information on the toxic effects of nanomaterial-adsorbed cadmium (Nano-Cd) on aquatic organisms is lacking. This study aimed to investigate the acute and sub-acute toxicity of Nano-Cd on Daphnia magna by using a method developed based on the standard Organisation for Economic Co-operation and Development (OECD) 202 guidelines. The toxicity of cadmium chloride (Cd²⁺), nano-manganese dioxide-cadmium (nMnO₂-Cd), 20nm nano-hydroxyapatite-cadmium (nHAP₂₀-Cd), and 40nm nano-hydroxyapatite-cadmium (nHAP₄₀-Cd) to D. magna was in the following order: Cd²⁺> nMnO₂-Cd > nHAP₂₀-Cd > nHAP₄₀-Cd. Further, nMnO₂-Cd, nHAP₂₀-Cd, and nHAP₄₀-Cd showed acute toxicity to D. magna of level II grade according to the Commission of the European Communities and OECD standards. Exposure to low and medium, but not high, Nano-Cd concentrations increased the activities of peroxidase, superoxide dismutase, catalase, and anti-superoxide anion. Thus, Nano-Cd, particularly at high concentrations, could exert oxidative damage in D. magna. An increase in Cd²⁺ and Nano-Cd concentrations gradually increased the malondialdehyde content, indicating cell membrane damage caused by the production of excessive O₂^-. Thus, the use of nanomaterials after adsorption of Cd is associated with a potential risk to aquatic organisms.

Effect and mechanism analysis of MnO2 on permeable reactive barrier (PRB) system for the removal of tetracycline

Effect of manganese dioxide (MnO₂) on tetracycline (TC) removal/degradation in zero-valent iron (ZVI) based permeable reactive barrier (PRB) system was investigated. To analyze the role of MnO₂, three different PRB columns packed with ZVI, ZVI and a layer of MnO₂, and MnO₂ were set up to investigate the removal effect and reaction mechanism of ZVI coupling with MnO₂ on TC removal, respectively. The results show that the removal efficiencies of three PRB columns are 65%, 85%, and 50%, respectively. MnO₂ could accelerate the transformation of Fe²⁺ into Fe³⁺ and combine with Fe³⁺ to degrade TC in different reaction sites in the ZVI-MnO₂ PRB system. Hydroxyl radicals (·OH) were produced in this process, which contributed to about 58.3% for the TC degradation. The UV-Vis spectrum demonstrated that A ring of TC was the main reaction site for interaction with Fe³⁺ and the BCD rings were crucial for interactions with MnO₂. On the basis of intermediates identified by LC-ESI-MS, the ring structure of TC was opened, and low-molecular-weight compounds were produced in ZVI-MnO₂ PRB system.

Long-term effects of combined divalent copper and tetracycline on the performance, microbial activity and community in a sequencing batch reactor

The long-term effects of combined divalent copper (Cu(II)) and tetracycline (TC) on the performance, microbial activity and community in a sequencing batch reactor (SBR) were investigated. The addition of Cu(II), TC or mixed Cu(II)/TC caused the decrease of the organics and nitrogen removal efficiencies, and their decreased degrees were the lowest at the addition of mixed Cu(II)/TC. The increase of mixed Cu(II)/TC concentrations in the influent did not change the antagonistic effects between Cu(II) and TC on nitrifying and denitrifying activities. Nitrifiers had higher tolerances to Cu(II), TC and mixed Cu(II)/TC than denitrifiers. Compared to the addition of Cu(II) or TC alone, the microbial community richness was higher at the addition of mixed Cu(II)/TC, while the microbial community diversity was lower. The increased protein (PN) in extracellular polymeric substances (EPS) was a protective response of bacteria to Cu(II), TC and mixed Cu(II)/TC.

Time-dependent and Pb-dependent antagonism and synergism towards Vibrio qinghaiensis sp.-Q67 within heavy metal mixtures

Toxicity interaction has aroused many researchers' interest in the combined toxicity of pollutants. Recently, some published studies have shown that the toxicity of some mixture pollutants is time dependent and well correlated with certain components in the mixture. Therefore, to investigate whether toxicity interaction is affected by the exposure time or certain components, synergism and antagonism within typical environmental contaminants of heavy metal mixtures were analyzed in different exposure times. Herein, three binary and one ternary mixture systems were designed by using three heavy metals: cadmium chloride, lead chloride (Pb) and manganese(ii) chloride tetrahydrate (Mn). For each mixture system, five mixture rays with different concentration ratios were arranged by direct equipartition ray design and uniform design ray methods. The toxicities of the three heavy metals and 20 mixture rays towards photobacteria Vibrio qinghaiensis sp.-Q67 (Q67) were determined by the established time-dependent microplate toxicity analysis (t-MTA) in different exposure durations of 0.25, 2, 4, 8 and 12 h. It was shown that the toxicities of three heavy metals (Cd, Pb and Mn) as well as their binary and ternary mixture rays to Q67 were also time dependent, but different metals or mixture rays showed different time characteristics. Surprisingly, some mixture rays exhibited antagonism or synergism with time dependency and the time characteristics varied in different mixture systems. Furthermore, the binary or ternary mixture systems with Pb displayed antagonism, while the Cd–Mn mixture system without Pb exhibited additive action or synergism, which indicated that Pb was probably the causative agent of antagonism produced by mixtures.

Toxicity interaction has gained much interest in the research of toxicity of mixture pollutants.

Carbon nanodot aqueous binding phase-based diffusive gradients in thin films device for measurement of dissolved copper and lead species in the aquatic environment

A reliable method for the determination of dissolved Cu²⁺and Pb²⁺species in waterviaa diffusive gradient in thin films (DGT) device using water-soluble carbon nanodots (CD) as the binding agent was developed (CD-DGT).

Effect of corrosion inhibitor benzotriazole on the uptake and translocation of Cd in rice (Oryza sativa L.) under different exposure conditions

Emerging contaminants that can complex with heavy metals might affect the speciation of coexisting metals and result in different ecological risks. As a widely used metal corrosion inhibitor, 1H-benzotriazole (BTR) is frequently detected in the environments, sometimes at very high levels. In this study, rice (Oryza sativa L.) was used to assess the ecological risk of combined exposure to cadmium (Cd) and BTR in plants and discuss the potential effects of exposure sequence on the uptake and translocation of Cd under hydroponic culture. In the combined exposure treatments, Cd concentration in rice significantly decreased when the molar ratio of BTR to Cd exceeded 1, while the oxidative damage of root was alleviated. In the sequential exposure treatments, an exposure to BTR accelerated the release of preabsorbed Cd from seedlings to the environment and increased the transport of Cd from the roots to shoots at high BTR concentrations. This demonstrates that the combined pollution effect of Cd and BTR is present not only in the environment but also in plants. With the decrease in Cd concentration in the roots, the electrolytic leakages from the roots also decreased, indicating that root damage repair was induced by the subsequent BTR exposure. BTR was mainly accumulated in the seedling roots. Preabsorbed BTR significantly increased Cd concentration in the roots of rice seedlings but inhibited Cd translocation from the roots to shoots of the rice seedlings.

Copper and Antibiotics: Discovery, Modes of Action, and Opportunities for Medicinal Applications

Copper is a ubiquitous element in the environment as well as living organisms, with its redox capabilities and complexation potential making it indispensable for many cellular functions. However, these same properties can be highly detrimental to prokaryotes and eukaryotes when not properly controlled, damaging many biomolecules including DNA, lipids, and proteins. To restrict free copper concentrations, all bacteria have developed mechanisms of resistance, sequestering and effluxing labile copper to minimize its deleterious effects. This weakness is actively exploited by phagocytes, which utilize a copper burst to destroy pathogens. Though administration of free copper is an unreasonable therapeutic antimicrobial itself, due to insufficient selectivity between host and pathogen, small-molecule ligands may provide an opportunity for therapeutic mimicry of the immune system. By modulating cellular entry, complex stability, resistance evasion, and target selectivity, ligand/metal coordination complexes can synergistically result in high levels of antibacterial activity. Several established therapeutic drugs, such as disulfiram and pyrithione, display remarkable copper-dependent inhibitory activity. These findings have led to development of new drug discovery techniques, using copper ions as the focal point. High-throughput screens for copper-dependent inhibitors against Mycobacterium tuberculosis and Staphylococcus aureus uncovered several new compounds, including a new class of inhibitors, the NNSNs. In this review, we highlight the microbial biology of copper, its antibacterial activities, and mechanisms to discover new inhibitors that synergize with copper.

Joint toxicity of cadmium and SDBS on Daphnia magna and Danio rerio

Information on joint toxicity is limited. To clarify the joint toxicity and the interactions among toxicants on different aquatic organisms, we investigated the acute toxicity of cadmium and sodium dodecyl benzene sulfonate, two chemicals with high concerns in Chinese waters, on the immobilization of Daphnia magna (D. magna) and the swimming behavior of Danio rerio (D. rerio). Our results illustrated that cadmium and sodium dodecyl benzene sulfonate expressed a synergistic effect on the immobilization of D. magna; and an antagonistic effect on the swimming speed D. rerio, but a synergistic effect on its vertical position in the water column. Based on the observed data, we found the independent action model was more appropriate than the concentration addition model in the prediction of their joint toxicity. Our results gave an example of the joint toxicity investigation, and aided to comprehensive the toxicity action mode of chemical mixtures.

Heavy Metal Induced Antibiotic Resistance in Bacterium LSJC7

Co-contamination of antibiotics and heavy metals prevails in the environment, and may play an important role in disseminating bacterial antibiotic resistance, but the selective effects of heavy metals on bacterial antibiotic resistance is largely unclear. To investigate this, the effects of heavy metals on antibiotic resistance were studied in a genome-sequenced bacterium, LSJC7. The results showed that the presence of arsenate, copper, and zinc were implicated in fortifying the resistance of LSJC7 towards tetracycline. The concentrations of heavy metals required to induce antibiotic resistance, i.e., the minimum heavy metal concentrations (MHCs), were far below (up to 64-fold) the minimum inhibition concentrations (MIC) of LSJC7. This finding indicates that the relatively low heavy metal levels in polluted environments and in treated humans and animals might be sufficient to induce bacterial antibiotic resistance. In addition, heavy metal induced antibiotic resistance was also observed for a combination of arsenate and chloramphenicol in LSJC7, and copper/zinc and tetracycline in antibiotic susceptible strain Escherichia coli DH5α. Overall, this study implies that heavy metal induced antibiotic resistance might be ubiquitous among various microbial species and suggests that it might play a role in the emergence and spread of antibiotic resistance in metal and antibiotic co-contaminated environments.