Study On The Resistance Of Salt-induced Hyperaccumulation Plant Endophyte Bacillus Sp. L14 To Quaternary Ammonium Compounds And Its Bioremediation

Quaternary ammonium salts are widely used in disinfectants and detergents.With human activities,the pollutant of quaternary ammonium salt?QACs?is threatening human health.A large number of facts have proved that quaternary ammonium salt,an environmental pollutant,has brought a lot harms to human beings,such as carcinogenic and teratogenic.If this hazard continues,human physical and mental health and the natural ecological environment will be inestimable threats.In recent years,quaternary ammonium salt can be treated by electric treatment,ultrasonic treatment,organic solvent or antibiotic treatment.These methods overhead cost is high,efficiency is lower,still need a lot of manpower to go carrying out,what important is processing process is quite complex.Bioremediation technology is an emerging treatment method in recent years.Although physical and chemical method is the most commonly used treatment method,it does not have the advantages of simplicity and economy of bioremediation technology.Therefore,bioremediation technology is considered as one of the most potential treatment methods of quaternary ammonium salt pollutants.However,quaternary ammonium salt pollutants are compounds that have the function of microbial disinfection.Therefore,the key to the treatment of quaternary ammonium salt pollutants with microbial remediation technology is to screen the strains resistant to quaternary ammonium salt from the ecosystem.1.A polymetallic resistant endogenous bacteria L14?EB L14?was isolated from Solanum nigrum L.,an ultra-cadmium rich plant,for biodegradation of quaternary ammonium compounds.According to the analysis of 16S rDNA,this endophyte belongs to bacillus.The endophyte was induced by different types of salt?NaCl,KCl,MgCl₂,CaCl₂?concentration.With the increase of inorganic salt concentration,the growth of bacterial strain EB L14 was inhibited,and the inhibition effect was obvious,which may be related to the water loss of microbial cells in the presence of high concentration of inorganic salt,affecting the normal growth and metabolism of microorganisms.In addition,it can be analyzed that the tolerance of EB L14 to different types of inorganic salts is not the same,the strongest resistance to Na⁺,K⁺,up to 80g/L,followed by Mg²⁺,up to 40g/L.And then finally we have Ca²⁺,which is 20g/L.2.After the induction of different types of salt concentration,it was found that the resistance to BACs(C₁₂BDMA-Cl/C₁₄BDMA-Cl)increased with the increase of salt concentration.Experiments on intracellular water content have shown that water loss occurs in cells under high salt concentration,leading to cell contraction and membrane pore reduction.BACs is not easy to enter the cell through the membrane pore,thereby reducing cell damage and enhancing the resistance of endogenous bacteria to BACs.3.In this paper,the removal effect of QACs high-tolerance and over-accumulation endophytes on BACs was also studied.The results showed that:the initial concentration of C₁₂BDMA-Cl was 5mg/L,and six resistant strains induced by different salt concentrations showed good degradation effect on BACs within 48 hours,and the degradation rate gradually increased with the increase of salt-induced concentration.The initial concentration of C₁₂BDMA-Cl was 10mg/L.The resistant strains induced by the first three salt concentrations were less resistant to BACs,and most of them died in the early stage of growth,so the degradation rate of BACs was lower than 20%.The latter three strains showed a degradation rate of over 80%for C₁₂BDMA-Cl within 48 hours,which was because of their high resistance.The initial concentration of C₁₂BDMA-Cl was 15mg/L,and only the last two resistant strains of these six different salt concentrations adapted to such a high concentration environment of C₁₂BDMA-Cl.However,most of the first four strains had already died in the early stage of growth due to their weak resistance,so their degradation rate of C₁₂BDMA-Cl was lower than 15%.The latter two strains had a good degradation effect on C₁₂BDMA-Cl within 48h,and the degradation rate was above 80%,because their resistance was relatively high,and the degradation rate was gradually increased.4.The degradation of C₁₄BDMA-Cl by EB L14 and its degradation pathway were studied.The formation of BDMA as the initial metabolite indicated that the calkyl-n cleavage was the first step of n-tetraalkyl benzyldimethyl ammonium chloride degradation.The formation of BMA may be due to further degradation of BDMA by demethylation.The superaccumulated plant endophytes selected in this experiment have good resistance to quaternary ammonium salt pollutants and have achieved a good removal effect,which provides a broad prospect for the application of microbial remediation technology in the treatment of quaternary ammonium salt pollutants.