Abstract
Magnetotactic bacteria synthesize intracellular membrane-enveloped magnetite bodies known as magnetosomes which have been applied in biotechnology and medicine. A series of proteins involved in ferric ion transport and redox required for magnetite formation have been identified but the knowledge of magnetosome biomineralization remains very limited. Here, we identify a novel OxyR homolog (named OxyR-Like), the disruption of which resulted in low ferromagnetism and disfigured nano-sized iron oxide crystals. High resolution-transmission electron microscopy showed that these nanoparticles are mainly composed of magnetite accompanied with ferric oxide including α-Fe2O3 and 𝜀-Fe2O3. Electrophoretic mobility shift assay and DNase I footprinting showed that OxyR-Like binds the conserved 5′-GATA-N{9}-TATC-3′ region within the promoter of pyruvate dehydrogenase (pdh) complex operon. Quantitative real-time reverse transcriptase PCR indicated that not only the expression of pdh operon but also genes related to magnetosomes biosynthesis and tricarboxylic acid cycle decreased dramatically, suggesting a link between carbon metabolism and magnetosome formation. Taken together, our results show that OxyR-Like plays a key role in magnetosomes formation.
Highlights
Magnetotactic bacteria (MTB) synthesize specialized intracellular membrane-bound organelles called magnetosomes that are arranged in chains by the action of the skeleton-like protein MamK and its binding partner MamJ (Bazylinski and Frankel, 2004; Komeili et al, 2006; Scheffel et al, 2006; Jogler and Schüler, 2009; Komeili, 2012)
It has been proven that magnetite biomineralization is mainly regulated by genes that encode proteins involved in ferric ion transport and redox, magnetosome vesicle biosynthesis and alignment, most of which are localized to a large unstable genomic region spanning 80–150 kb in length in different MTBs called the magnetosome island (MAI) (Grunberg et al, 2004; Murat et al, 2010)
Some genes in the MAI encode proteins related to magnetosome synthesis, viz., MamA and MamE, which are involved in the sorting and activation of mam genes (Komeili et al, 2004; Quinlan et al, 2011; Zeytuni et al, 2011; Hershey et al, 2016; Nguyen et al, 2016; Raschdorf et al, 2016); MamL, Q, B, I, E, M, and O, which function in the invagination of magnetosome vesicles (Raschdorf et al, 2016); and MamY, which influences the shape of magnetosome vesicles (Tanaka et al, 2010)
Summary
Magnetotactic bacteria (MTB) synthesize specialized intracellular membrane-bound organelles called magnetosomes that are arranged in chains by the action of the skeleton-like protein MamK and its binding partner MamJ (Bazylinski and Frankel, 2004; Komeili et al, 2006; Scheffel et al, 2006; Jogler and Schüler, 2009; Komeili, 2012). It has been proven that magnetite biomineralization is mainly regulated by genes that encode proteins involved in ferric ion transport and redox, magnetosome vesicle biosynthesis and alignment, most of which are localized to a large unstable genomic region spanning 80–150 kb in length in different MTBs called the magnetosome island (MAI) (Grunberg et al, 2004; Murat et al, 2010). Deletion of feoB1 reduces the size and quantity of magnetosomes and decreases ferrous ion uptake of the cell (Rong et al, 2008)
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