Research On The Time-Dependent Cross-Phenomena And Mechanism Of Aliivibrio Fischeri With The Mixtures Of Antimicrobial Agents

With the large-scale production and wide application of antimicrobial agents,more and more antimicrobial agents will be discharged into the environment through various ways,posing a great threat to the ecosystem and human health.Antimicrobial agents discharged into the environment are often low dose and mixed exposure,the low dose of antimicrobial agent may produce the Hormesis effect of low concentration promotion and high concentration inhibition on organisms,and the mixed exposure of antimicrobial agent often produces cross-phenomenon.The cross-phenomenon refers to the cross-phenomenon between the actual concentration-response curve(CRC)of the mixture and its prediction model curve when the model method is used to distinguish the combined toxicity of the mixture,which shows that the combined toxicity mode also changes with the change of the mixture concentration.At present,although a large number of cross-phenomenon have been reported,the research on the cross-phenomenon mostly stays in the surface analysis,lack of in-depth exploration.So what kind of cross-phenomenon do the mixtures of antimicrobial agents in the environment have on bacteria?Does cross-phenomenon change with different growth stages of the bacteria?These are all worth exploring.The cross-phenomenon is a phenomenon that changes with concentration,and the compound that is produced by this Hormesis also changes with concentration.Could cross-phenomenon be related to Hormesis?How does Hormesis regulate this cross-phenomenon?None of this has been definitively determined.Therefore,it is necessary to deeply study the relationship between cross-phenomenon and Hormesis,which will help the environmental protection department to understand the joint exposure risk of pollutants more comprehensively,so as to carry out ecological risk assessment of mixed pollutants more effectively.In this study,Aliivibrio fischeri(A.fischeri)was taken as the model organism,sulfonamides(SAS),tetracycline hydrochloride(TH),quorum sensing inhibitors(Benzofuran-3(2H)-one(B3O),nano-silver(AgNP)and polypeptides were taken as the research objects.Their single toxicity to A.fischeri bioluminescence were measured at13-24 h.At the same time,SAs-TH,as the representative of the mixtures of traditional antibacterial agent and traditional antibacterial agent,SAs-B3O,as the representative of the mixtures of traditional antibacterial agent and new antibacterial agent.AgNP-polypeptides,as the representative of the mixtures of new antibacterial agent and new antibacterial agent,their joint toxicity were measured in 13 to 24 h for A.fischeri bioluminescence.In this paper,the time-dependent cross-phenomena of the mixtures of antimicrobial agents to A.fischeri was studied,and the law of time-dependent cross-phenomena was summarized.Based on A.fischeri's bacterial quorum sensing(QS)system and the Hormesis effect mechanism of antimicrobial agents,the reason of the time-dependent cross-phenomena was discussed.The main research contents and conclusions are as follows:(1)The single toxicity of SAS,TH,B3O,AgNP and polypeptide to A.fischeri bioluminescenceThe single toxicity of 5 kinds of SAs,5 kinds of polypeptide,a kind of TH,a kind of B3O and a kind of AgNP in 13 to 24 h for A.fischeri were determined from 13 h to24 h,by comparing the EC₅₀ of 24 h,the order of toxicity of SAs and B3O was SMM>SQ>SMR>SD>SM>TH>B3O.The order of toxicity of AgNP and polypeptides was polymyxin B sulphate>AgNP>colistin sulfate>kanamycin sulfate>capreomycin sulfate>bacitracin.Except that SMM,kanamycin sulfate and colistin sulfate did not have Hormesis effect on A.fischeri's bioluminescence,the rest of SAS,TH,B3o,AgNP and polypeptides all had Hormesis effect on A.fischeri's bioluminescence.At the same time,with the increase of exposure time,the concentration corresponding to the maximum promotion effect of compounds on A.fischeri's bioluminescence is generally increasing,and the concentration range of promoting effect of compounds is also gradually shifting to the right.We hypothesized that the compounds acts on A.fischeri's QS system and thus shows a time-dependent Hormesis effect.(2)The combined toxicity of the mixtures of SAS-TH,SAS-B3O and AgNP-polypeptideThe combined toxicity of 4 kinds of SAS-TH,5 kinds of SAS-B3O and 5 kinds of AgNP-polypeptides to A.fischeri bioluminescence at 13-24 h was determined.The results showed that,except that AgNP-polymyxin sulfate B did not show Hormesis effect and cross-phenomena on A.fischeri's bioluminescence,the other binary mixtures of AgNP-polypeptide,SAS-TH and SAS-B3O all have Hormesis effect and cross-phenomena on A.fischeri's bioluminescence.The cross-phenomena not only changes with the concentration of the mixture,but also changes with the increase of exposure time.With the increase of exposure time,the concentration range of the cross-phenomena gradually shifted to the right as a whole.(3)The time-dependent cross-phenomena and mechanism of the binary mixtures of SAS-TH,SAS-B3O and AgNP-polypeptide were studied,and the exposure risks of the binary mixtures of traditional antibacterial agent and traditional antibacterial agent,traditional antibacterial agent and new antibacterial agent and new antibacterial agent and new antibacterial agent were compared.Summarized the trend of time-dependent cross-phenomena for four kinds of the binary mixtures of SAs and TH,five kinds of the binary mixtures of SAs and B3O and five kinds of the binary mixtures of AgNP and peptide from 13 to 24 h,and based on the trend of time-dependent cross-phenomena for the binary mixtures,sums up the time-dependent cross-phenomena for the binary mixtures are A(synergy)?B(antagonism?additive?synergy)?C(antagonism)?D(synergy?additive?antagonism).It is speculated that this kind of time-dependent cross-phenomena may be related to the Hormesis effect induced by antimicrobial agents on A.fischeri's QS system.In addition,whether SM is mixed with the traditional antimicrobial agent TH or the new antimicrobial agent B3O,its exposure risk is very high in the high concentration area.Compared with TH,the ecological risk of B3O mixed with SD,SQ and SMR antibacterial agents was greater in the high concentration area.The binary mixtures of new antibacterial agent and new antibacterial agent are at greater risk of environmental exposure in high-concentration areas than the binary mixtures of traditional antibacterial agent and traditional antibacterial agent and the binary mixtures of traditional antibacterial agent and new antibacterial agent.The research in this paper is beneficial to a more comprehensive and in-depth understanding of the cross-phenomena of mixed pollutants,and provides a new idea for the study of the cross-phenomena mechanism from the perspective of QS system and Hormesis,and provides data support and theoretical reference for ecological risk assessment of mixed pollutants.