Intracellular biomineralization in bacteria

Abstract

Microorganisms have populated the Earth for billions of years and their activities are important forces shaping our planetary environments through biogeochemical cycles. In particular, microbial biomineralization that selectively take up environmental elements and deposit minerals either intracellularly or extracellularly is of great interest, because these processes play vital roles in the global cycles of numerous elements, such as Fe, Mn, Ca, As, O, S, and P, etc. Biominerals, the products of biomineralization, not only serve as important biosignatures for the search of traces of past life and the reconstruction of ancient environments but also have many important commercial applications.Recent advances in sequencing technologies, molecular analyses and approaches for assaying protein functions pave the way for rapid progress in microbial biomineralization research. The objective of this research topic is to highlight the latest advances in our understanding of intracellular biomineralization in bacteria, with a focus on the magnetotactic bacteria (MTB), a group of phylogenetically diverse microbes synthesizing magnetic minerals of magnetite (Fe 3 O 4 ) and/or greigite (Fe 3 S 4 ) magnetosomes in cells. Magnetosomes are generally less than 150 nm in length, covered by lipid bilayer membrane and organized into one or multiple chain structures that act like a compass needle to facilitate the navigation of MTB using the Earth's magnetic field. The uniform nano sizes, superior magnetic properties and perfect chain arrangement suggest a strict genetic control of magnetosome synthesis in MTB cells, which provides an attractive model system for investigating the mechanisms of bacterial intracellular biomineralization. This research topic provides a selection of interesting and challenging topics of research on the diversity, ecology, evolution, genomics, and biochemistry of MTB. The applications of magnetosomes in biotechnology and paleoenvironmental reconstruction are also covered here.This research topic begins with a review on the relationship between all known magnetosome crystal habits and the phylogenetic affiliations of MTB (Pósfai et al., 2013), which serves as guide to better understand the evolutionary history of magnetosome formation and magnetotaxis in MTB. Following this review, Morillo et al. (2014) report the first cultivation and genomic characterization of a south-seeking Alphaproteobacteria magnetotactic coccus Magnetofaba australis strain IT-1 from the Southern Hemisphere. The findings of their study provide important clues to the evolution of magnetotactic Alphaproteobacteria. Oestreicher et al. (2013) examine the morphological and phylogenetic diversity of MTB in a freshwater lake containing microbialites. Their results raise the interesting question of whether MTB magnetosomes could be preserved in microbialites and serve as robust biomarkers. Kong et al. (2014) investigate the swimming behavior of a rod-shaped magnetotactic Nitrospirae, with hundreds bullet-shaped magnetite magnetosomes per ce...