Recent advances in studies on magnetosome‐associated proteins composing the bacterial geomagnetic sensor organelle

Abstract

Magnetotactic bacteria (MTB) generate a membrane‐enclosed subcellular compartment called magnetosome, which contains a biomineralized magnetite or greigite crystal, an inner membrane–derived lipid bilayer membrane, and a set of specifically targeted associated proteins. Magnetosomes are formed by a group of magnetosome‐associated proteins encoded in a genomic region called magnetosome island. Magnetosomes are then arranged in a linear chain–like positioning, and the resulting magnetic dipole of the chain functions as a geomagnetic sensor for magneto‐aerotaxis motility. Recent metagenomic analyses of environmental specimens shed light on the sizable phylogenetical diversity of uncultured MTB at the phylum level. These findings have led to a better understanding of the diversity and conservation of magnetosome‐associated proteins. This review provides an overview of magnetosomes and magnetosome‐associated proteins and introduces recent topics about this fascinating magnetic bacterial organelle.

Understanding Biomineralization Mechanisms to Produce Size-Controlled, Tailored Nanocrystals for Optoelectronic and Catalytic Applications: A Review

“…168 Mam proteins are colocalized to magnetosomes; however, they are not necessarily all complexed with one another. 168,169 MamE, MamO, and MamP are all necessary contributors to biomineralization, with individual knockouts showing decreased or abolished activity. 170−173 Several Mam proteins together template particle formation, including MamC, MamE, MamF, MamG, and MamO.…”

“…Figure 11, from Taoka et al, illustrates the genes and proteins involved in membrane growth, highlighting the growth of empty magnetosome membranes, then crystal-containing magnetosome membranes. 168 A cohesive examination of MamE, MamO, MamM, and MamP by Wan et al reveals the corresponding inactivity to individual gene knockouts, where-in MamE knockout results in inhibited crystal maturation (size limited to 30 nm), MamO and MamM knockouts individually result in empty magnetosome membranes, and MamP knockout results in smaller crystals, likely due to steric hindrance associated with less membrane growth. Accordingly, MamO and MamP appear crucial for particle nucleation, while MamE and MamP seem to regulate particle growth.…”

“…In magnetosomes, the Mam (magnetosome membrane associated) and Mms (magnetosome membrane specific) proteins have been a central focus for magnetite biomineralization in vitro ; however, no singular protein appears to be capable of this biomineralization alone . Mam proteins are colocalized to magnetosomes; however, they are not necessarily all complexed with one another. , MamE, MamO, and MamP are all necessary contributors to biomineralization, with individual knockouts showing decreased or abolished activity. − …”

“…Within membrane encapsulation, the size of invaginated membrane (Figure ) seems to play a critical role in reaching sufficiently high concentrations for nucleation, then guiding subsequent particle growth to accompany membrane growth. Figure , from Taoka et al., illustrates the genes and proteins involved in membrane growth, highlighting the growth of empty magnetosome membranes, then crystal-containing magnetosome membranes . A cohesive examination of MamE, MamO, MamM, and MamP by Wan et al reveals the corresponding inactivity to individual gene knockouts, where-in MamE knockout results in inhibited crystal maturation (size limited to 30 nm), MamO and MamM knockouts individually result in empty magnetosome membranes, and MamP knockout results in smaller crystals, likely due to steric hindrance associated with less membrane growth.…”

“…Growth stages of invaginated magnetosome membranes as empty magnetosome membranes (EMM) and crystal-containing magnetosome membranes (CMM). Reproduced with permission from ref . Copyright 2023 John Wiley & Sons Books.…”