1. The first aspect is to study the interaction between surfactants and plasmid DNA, and the effect of surfactants on DNA function, in order to understand the biological process in cells through its mechanism of action, or to provide new ways and new ideas for the treatment of human diseases.

Using electroactive methylene blue (MB) as a probe, the interaction between several surfactants and DNA was studied by cyclic voltammetry, UV-vis spectrum and AC impedance method. It is found that anionic, cationic and nonionic surfactants can combine with DNA molecules fixed on the electrode surface through hydrophobic interaction and electrostatic interaction, change the state of DNA on the electrode surface, and then affect the electrochemical behavior of electroactive small molecules. There is mainly electrostatic repulsion between anionic surfactants and DNA, and there is also some hydrophobic binding, which reduces the redox peak current of MB. Cationic surfactants cetyltrimethyl ammonium bromide and dodecyl trimethyl ammonium chloride all enhance the electrochemical response of MB in a certain concentration range, while cetylpyridine and octadecyl pyridine bromide show inhibitory effects, which are hydrophobic and electrostatic attractive to DNA. The combination of nonionic surfactant and DNA is weak, which mainly affects the conformation of DNA by changing the properties of solution (such as viscosity, polarity and dielectric constant), thus leading to the weak change of MB electrochemical parameters. In addition, the length of hydrophobic chain of surfactant and the size of polar head group also have certain influence on the action process.

2. In the second aspect, there are many researches at present, mainly to screen bacterial plasmids that can degrade surfactants in sewage, in order to obtain plasmids that can degrade surfactants efficiently, and use them to transform bacteria, so as to obtain strains that can degrade sewage efficiently for environmental treatment.

The experimental principle is generally as follows: firstly, the plasmids of various strains are extracted from sewage and transformed into other strains, and the changes of their ability to digest surfactants are observed, so as to know whether these plasmids can degrade surfactants and the size of their degradation ability. Because this work is of great significance in sewage treatment, there are many studies now.

The following is the conclusion of a document, which basically summarizes this aspect.

Although there have been some reports on bacteria in water polluted by surfactants, the molecular mechanism of their degradation has not been reported. How to select high-efficient degrading strains from the perspective of molecular biology is not only related to the study of microecosystem, but also closely related to the study of molecular genetics (degrading genes). The results of this study show that most of the excellent bacteria that can survive in surfactant wastewater contain plasmids, and the detection rate is as high as 64.9%. Large plasmid is the main strain, accounting for 84.4% of plasmid strains. In a certain concentration range, the large plasmid content of the strain increased with the increase of surfactant concentration. In the process of evolution, large plasmids may aggregate a group of functional structures related to two or more small plasmids through recombination and selection, that is, the so-called "composite replicon", and finally have the function of degrading surface inclusions. Multi-drug resistance found in nature is a kind of "natural compound replica", and the evolution process of large plasmid of bacteria living in sewage with high surfactant concentration for a long time may be similar to that of multi-drug resistance plasmid. In this study, some large plasmid strains were found to be degraded.

Working energy of surfactant. The existence of such particles is directly related to the purification of surfactant wastewater. At the same time, this plasmid can also be transferred to other strains by conjugation, so that other strains can also obtain degradation ability. Therefore, the large plasmid is the first noteworthy object in the cultivation of surfactant-degraded seedlings. As for the effect of containing one or more small plasmids on the growth and reproduction of the strain, it needs to be studied after praise. According to the results of this study, it is expected that further genetic research on surfactant particle degradation will help solve some important problems in microbial treatment of surfactant wastewater.

Theoretical and practical issues.