Joint Effects And Mechanisms Of Binary Toxicity Of Sulfa Antibiotics And Quorum Sensing Inhibitors To Vibrio Fischeri

Because of their antibacterial ability, antibiotics were widely used in agriculture, fisheries, animal husbandry and other fields since they were found. Due to the overuse of excess, resistance gene and a serious environment problem emerged. Quorum sensing inhibitors as antibiotic alternatives had been proposed to solve the problem of antibiotics abuse. Inevitably, both of them will coexist in environment for a long time in the future. So the research of joint effects of antibiotics and quorum sensing inhibitors and whether they have hormesis dose-responses provided a theoretical basis for the ecological environment risk assessment and drug combination. In addition, the research has important scientific significance.In this study, the acute single toxicity, acute mixture toxicity, chronic single toxicity, chronic mixture toxicity, chronic single hormesis dose-responses and chronic joint hormetic dose-responses of sulfa antibiotics and three kinds of quorum sensing inhibitors to Vibro fischeri were determined. The mechanism were explored and the reasons of hormesis were analyzed by calculating physical and chemical parameters, protein homology modeling, molecular docking and detecting indole in bacteria. The results are as follows.(1) The results of acute binary toxicity of sulfa antibiotics and furanon are synergic and additive. And the results of acute binary toxicity of sulfa with porrolone and pyrrole are additive and antagonistic. The reason of the different effects may be that they have different capacity of H+.(2) The joint effect of chronic binary toxicity of three kinds of quorum sensing inhibitors and sulfa antibiotics are both antagonistic. The reason may be that sulfa antibiotics promote the expression of Lux R protein. And the quorum sening inhibitors conbined with Lux R. So the effect is chronic antagonistic.(3) 12 kinds of sulfa antibiotics can increase the light intensity of vibrio fischeri in low dose and all show hormesis dose-responses. The reason is that sulfa antibiotics promote the expression of Lux R protein. The main effect of Lux R is to regulate the light. We inferred that indole isn’t the substance who promote the expression of Lux R in vibrio fischeri. Therefor the mechanism of hormesis need to further research.(4) The hormesis of two substance who have hormesis dose-responses were evident after mixed. We use the area of closed by effect curve and straight line of Y=0 to evaluate the hormetic effect. We calculate the area using Brain-Cousens model and then create a model for area of single hormesis and joint hormesis. The R2 of the equation is greater than 0.64, so the equation has statistically significant. Therefor we can use area of single hormesis to forcast the area of joint hormesis.