bims-mricoa 2022-10-09 papers

Issue of 2022–10–09
three papers selected by
Merve Yavuz, Bilkent University

Biomater Sci. 2022 Oct 03.

Magnetotactic bacteria AMB-1 with active deep tumor penetrability for magnetic hyperthermia of hypoxic tumors.

Xin Chen, Liwen Lai, Xiang Li, Xintong Cheng, Xinxin Shan, Xiangqing Liu, Liqun Chen, Guangliang Chen, Guoming Huang.

Tumor hypoxia is a great physiological barrier for tumor treatment. The development of efficient detection and treatment methods for tumor hypoxia has great scientific and clinical significance. In this work, we investigated the potential of magnetotactic bacteria AMB-1 for magnetic resonance imaging (MRI)-guided magnetic hyperthermia treatment of hypoxic tumors. Our investigations reveal that AMB-1 bacteria can selectively migrate to the hypoxic regions of solid tumors due to their anaerobic characteristics, showing active deep tumor penetrability. Moreover, AMB-1 bacteria exhibit high MRI contrast and magnetic heating performances because of the excellent magnetic performance of their magnetosomes. In vivo studies demonstrate that AMB-1 can not only generate T2-weighted contrast signals in tumor tissue, but also efficiently ablate hypoxic solid tumors through the magnetic hyperthermia effect. We believe that this novel microbial therapy can be a potential weapon for hypoxic tumor treatment.

DOI: https://doi.org/10.1039/d2bm01029a

ACS Nano. 2022 Oct 06.

Magnetothermal Control of Temperature-Sensitive Repressors in Superparamagnetic Iron Nanoparticle-Coated Bacillus subtilis.

Emily M Greeson, Cody S Madsen, Ashley V Makela, Christopher H Contag.

Superparamagnetic iron oxide nanoparticles (SPIONs) are used as contrast agents in magnetic resonance imaging (MRI) and magnetic particle imaging (MPI), and resulting images can be used to guide magnetothermal heating. Alternating magnetic fields (AMF) cause local temperature increases in regions with SPIONs, and we investigated the ability of magnetic hyperthermia to regulate temperature-sensitive repressors (TSRs) of bacterial transcription. The TSR, TlpA39, was derived from a Gram-negative bacterium and used here for thermal control of reporter gene expression in Gram-positive, Bacillus subtilis. In vitro heating of B. subtilis with TlpA39 controlling bacterial luciferase expression resulted in a 14.6-fold (12 hours; h) and 1.8-fold (1 h) increase in reporter transcripts with a 10.0-fold (12 h) and 12.1-fold (1 h) increase in bioluminescence. To develop magnetothermal control, B. subtilis cells were coated with three SPION variations. Electron microscopy coupled with energy dispersive X-ray spectroscopy revealed an external association with, and retention of, SPIONs on B. subtilis. Furthermore, using long duration AMF we demonstrated magnetothermal induction of the TSRs in SPION-coated B. subtilis with a maximum of 5.6-fold increases in bioluminescence. After intramuscular injections of SPION-coated B. subtilis, histology revealed that SPIONs remained in the same locations as the bacteria. For in vivo studies, 1 h of AMF is the maximum exposure due to anesthesia constraints. Both in vitro and in vivo, there was no change in bioluminescence after 1 h of AMF treatment. Pairing TSRs with magnetothermal energy using SPIONs for localized heating with AMF can lead to transcriptional control that expands options for targeted bacteriotherapies.

Keywords: Superparamagnetic iron oxide nanoparticles; bacterial transcriptional control; magnetic hyperthermia; magnetothermal control; temperature-sensitive repressors

DOI: https://doi.org/10.1021/acsnano.2c06239

ACS Synth Biol. 2022 Oct 07.

Efficient Bacterial Genome Engineering throughout the Central Dogma Using the Dual-Selection Marker tetAOPT.

Carolyn N Bayer, Ana G V Sepulchro, Maja Rennig, Morten H H Nørholm.

Engineering of bacterial genomes is a fundamental craft in contemporary biotechnology. The ability to precisely edit chromosomes allows for the development of cells with specific phenotypes for metabolic engineering and for the creation of minimized genomes. Genetic tools are needed to select for cells that underwent editing, and dual-selection markers that enable both positive and negative selection are highly useful. Here, we present an optimized and easy-to-use version of the tetA dual-selection marker and demonstrate how this tetAOPT can be used efficiently to engineer at different stages of the central dogma of molecular biology. On the DNA level, tetAOPT can be used to create scarless knockouts across the Escherichia coli genome with efficiency above 90%, whereas recombinant gene integrations can be achieved with approximately 50% efficiency. On the RNA and protein level, we show that tetAOPT enables advanced genome engineering of both gene translation and transcription by introducing sequence variation in the translation initiation region or by exchanging promoters. Finally, we demonstrate the use of tetAOPT for genome engineering in the industrially relevant probiotic strain E. coli Nissle.

Keywords: Escherichia coli; Escherichia coli Nissle; dual-selection marker; genome engineering; recombineering; tetA

DOI: https://doi.org/10.1021/acssynbio.2c00345