Enhanced Silver Nanoparticle Synthesis by Escherichia Coli Transformed with Candida Albicans Metallothionein Gene

Abstract

In this study, the metallothionein gene of Candida albicans (C. albicans) was assembled by polymerase chain reaction (PCR), inserted into pUC19 vector, and further transformed into Escherichia coli (E. coli) DH5α cells. The capacity of these recombinant E. coli DH5α cells to synthesize silver nanoparticles was examined. Our results demonstrated that the expression of C. albicans metallothionein in E. coli promoted the bacterial tolerance to metal ions and increased yield of silver nanoparticle synthesis. The compositional and morphological analysis of the silver nanoparticles revealed that silver nanoparticles synthesized by the engineered E. coli cells are around 20 nm in size, and spherical in shape. Importantly, the silver nanoparticles produced by the engineered cells were more homogeneous in shape and size than those produced by bacteria lack of the C. albicans metallothionein. Our study provided preliminary information for further development of the engineered E. coli as a platform for large-scale production of uniform nanoparticles for various applications in nanotechnology. studies have been seeking to integrate MTs in creating biological platforms for the production of metal NPs. Engineered bacteria expressing MT and/or phytochelatins have been shown to be able to produce diverse nanoparticles [9][10][11].A critical aspect in developing a microbial platform for NP synthesis is choosing a proper host microorganism. It is ideal that a biofactory can make NPs with consistent properties for their applications in various field of nanotechnology. Many types of microorganism have been shown to be able to synthesize various metal NPs, but with diverse properties [12][13][14][15][16]. In addition, the conditions for cultivation and maintenance of microorganisms vary for different species [14][15][16]. Among the microorganisms able to serve as potential biofactories for metal NP synthesis, the readily available bacteria, E. coli, is of particular interest, due to the relatively easy and simple procedures to grow, maintain and manipulate them in the lab. The potential of engineered E. coli as a common platform for synthesis of diverse NP has been explored; however, the efficiency of NP synthesis by the engineered bacteria and the potential to upgrade to large scale NP production were not examined [9][10][11].The goal of this study was to provide preliminary evidence for exploiting engineered E. coil as a platform for the large-scale production of metal NPs with controlled morphological properties. In this study, we chose C. albicans MT as a target protein and transferred a PCR-assembled C. albicans MT gene into E. coli DH5α cells to examine whether expression of C. albicans MT in E. coli would improve bacterial NP synthesis.Compared to E. coli MT, which has four cysteine out of 56 residues (7.1%), the C. albicans MT has a relatively high content of cysteine residues (15.8%). Importantly, the C. albicans has four repeats of Cys-Xaa-Cys presumably for binding metal ions, such as copper [17,18]. To examine whether the...

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“…E. coli was also reported to form different metallic nanoparticles, including silver, gold, copper, iron, etc. [20,21]. We incubated the supernatant of 24 h grown culture of P. putida and E. coli with silver salt for the next 24-48 h. The extracellular supernatant helped in the reduction of the silver salt to nanoparticles.…”

Bacteria Exposed to Silver Nanoparticles Synthesized by Laser Ablation in Water: Modelling E. coli Growth and Inactivation

“…DH5α is commonly used laboratory E. coli strain to maintain and amplify small plasmid DNA [43]. More importantly, it is often used in fundamental research of a wide range of new potential antibacterials [44][45][46][47] and even for the production of silver nanoparticles upon transformation [48]. Additionally, it seemed reasonable to model growth curves of this strain since we have thoroughly investigated its growth parameters [40].…”

Microbe-Mediated Biosynthesis of Nanoparticles: Applications and Future Prospects

“…Recently, Yuan et al, 2019 also reported the fabrication of AgNPs by using a transformed strain of E. coli containing metallothionein in the gene from Candida albicans . The authors concluded that the transformed E. coli can be further used for the enhanced production AgNPs [ 78 ].…”