Determination of the role of porin proteins (OmpA, OmpC, OmpF. OmpG, OmpT, LamB and PhoE) under metal stress in Escherichia coli w3110

Metals are very important for microorganisms. Generally, metals act as the structural or catalytic component of biomolecules important for basic biological processes. However, heavy metals such as copper, cadmium, lead, zinc, nickel, mercury and chromium, which accumulate in nature for various reasons, have become one of the most important environmental problems that negatively affect microorganisms. Homeostasis of metals in the cell is primarily concerned with the regulation of metal transport into and out of the cell. Therefore, porin proteins, which have a role in membrane permeability, have an important role in the development of metal resistance. In this study, the roles of outer membrane channel proteins OmpA, OmpC, OmpF, OmpG, OmpT, LamB, and PhoE porin proteins of E. coli W3110 against cobalt, copper, zinc, cadmium and nickel metals were determined. In addition, the roles of CueR, RcnR, NikR, Zur, CpxAR and CusSR proteins on porin genes, which are involved in metal homeostasis, were investigated. E. coli W3110 mutants and complement cells were obtained for use in the study. The roles of porin proteins against cobalt, copper, zinc, cadmium and nickel metals were determined by growth and survival experiments of wild type E. coli W3110 and porin mutants. The change in the expression levels of porin genes in the presence of the studied metals and the role of CueR, RcnR, NikR, Zur, CpxAR and CusSR proteins in this change were determined by real-time PCR. Finally, using attenuated total reflectance (ATR)–Fourier transform infrared (FTIR) spectroscopy, the molecular profiles occurring in wild E. coli W3110 exposed to metal and different porin mutants were compared. Statistical analyzes of the data obtained at the end of the studies were performed in the GraphPAD Prism 8.3.0 program according to the 2way ANOVA test and their significance levels were determined according to the P≤ 0.05 system. As a result of the study, it was determined that the absence of OmpA and OmpC proteins in general sensitized the cell, while the absence of OmpF and LamB increased resistance to metal. It was determined that the synthesis of ompA, ompC, ompF genes decreased, while the synthesis of ompG and phoE genes increased significantly in wild type E. coli W3110 at all metal stresses. It was determined that the synthesis of the ompT gene was significantly suppressed in cadmium metal, and the synthesis of lamB increased in the presence of Cu and Zn, but decreased in the presence of Cd and Co. These results show that porin proteins have an vi important role in developing metal resistance. In the suppression of ompF and lamB genes, which were determined to have an important role in Cd stress, NikR and CueR from suppression of ompT gene and increase of phoE gene; and from the increase of ompG, it was determined that NikR and Zur had roles. It was observed that NikR from the suppression of ompC and ompF, and RcnR and NikR from the increase of phoE and ompG in Co stress. In Cu stress, the suppression of ompA resulted in CpxA and CusSR; suppression of ompC CueR and CusS; CusS inhibition of ompF and ompT syntheses; It was determined that the increase of ompG was under the control of NikR and CusR and the increase of phoE was under the control of NikR, Zur, CpxR and CusSR systems. It was determined that CueR, RcnR, NikR and Zur proteins did not have a role in the suppression of ompA, which was determined significantly in Ni stress, from the increase of ompG and phoE, but under the control of a different regulator. Finally, under Zn stress, ompA and ompC were found to be controlled by NikR and Zur, and ompT by NikR. This study can help characterize metals detoxification efficiency and guide for obtaining active living cells to be used in bioremediation.