Study On The Effect Mechanism Of Triclocarban On The Paracoccus Denitrificans

Triclocarban(TCC)is a broad-spectrum chlorinated aromatic hydrocarbon antibacterial agent containing two benzene rings and two amide bonds.It is widely used in detergents,textiles,plastics,children's toys,cosmetics and other personal care products.The global pandemic of SARS-Cov-2 may cause the continuously increasing use of antibacterial agents,such as triclocarban,but the environmental risks have not yet been fully assessed.In order to fill the vacancy in the study of the effect of antibacterial agents on the denitrification function of purely cultured microorganisms,this paper selected typical denitrifying bacteria,Paracoccus denitrificans PD1222,as the research object.And then the effect of different environmental concentrations of triclocarban(0,25,50,and 75?g/L)on its denitrification function was explored.The results of denitrification experiments showed that the accumulation of strong greenhouse gas N₂O with 25?g/L TCC was about813 times that of the control group.When the concentration of TCC was 75?g/L,the denitrification process was completely inhibited.The iTRAQ quantitative proteomics technology was used to analyze the expression abundance,functional annotation and network interaction of differential proteins of Paracoccus denitrificans in the case of 25?g/L TCC and without TCC.The result of Paracoccus denitrificans'differential proteins between the control group and 25?g/L TCC culture conditions showed that there were 164 significantly different proteins,of which 71 were expressed up-regulated proteins and 93 were expressed down-regulated proteins.The main reason for the large accumulation of N₂O is that Nos Z,a functional enzyme responsible for reducing N₂O to N₂,was significantly inhibited by TCC.Secondly,the pathways related to carbon metabolism and electron production and transfer,such as oxidative phosphorylation,tricarboxylic acid cycle,pyruvate metabolism,and siderophore non-ribosomal polypeptide biosynthesis were all affected.Moreover,the ribosomal protein was the most critical nodal protein speculated from the differential protein interaction network.In order to further explore the feasibility of TCC hydrolytic detoxification for recovering the normal function of Paracoccus denitrificans,the TCC-degrading bacterium,Ochrobactrum sp.TCC-2,and Paracoccus denitrificans were co-cultured to compare the difference in denitrification efficiency.When the two strains performed the combined denitrification,the Ochrobactrum sp.played the TCC hydrolysis effect,which is beneficial to the denitrification of Paracoccus denitrificans and reduced the N₂O-N emissions by 2 orders of magnitude.At the same time,Paracoccus denitrificans can quickly reduce the toxic intermediate product NO₂^-,and recovered the growth of Ochrobactrum sp.The two strains played their respective characteristics,and coordinated to promote the normal denitrification progress.This paper provided a theoretical basis for exploring the molecular mechanism of triclocarban affecting the functional microorganism's denitrification process.It also pointed out that when evaluating the environmental effects of antibiotics or antibacterial agents,consideration should be given to their potential risks to the biogeochemical nitrogen cycle and greenhouse gas emissions.It also provided an important reference for the effective evaluation of antibacterial agents and other emerging organic pollutants on global warming data.In addition,this paper provides a certain scientific basis and theoretical guidance for the traditional sewage treatment to face the toxic challenge of antibacterial agents and other emerging organic pollutants.