Comparative genomic analysis of magnetotactic bacteria from the D eltaproteobacteria provides new insights into magnetite and greigite magnetosome genes required for magnetotaxis

Abstract

Summary Magnetotactic bacteria ( MTB ) represent a group of diverse motile prokaryotes that biomineralize magnetosomes, the organelles responsible for magnetotaxis. Magnetosomes consist of intracellular, membrane‐bounded, tens‐of‐nanometre‐sized crystals of the magnetic minerals magnetite ( Fe 3 O 4 ) or greigite ( Fe 3 S 4 ) and are usually organized as a chain within the cell acting like a compass needle. Most information regarding the biomineralization processes involved in magnetosome formation comes from studies involving A lphaproteobacteria species which biomineralize cuboctahedral and elongated prismatic crystals of magnetite. Many magnetosome genes, the mam genes, identified in these organisms are conserved in all known MTB . Here we present a comparative genomic analysis of magnetotactic D eltaproteobacteria that synthesize bullet‐shaped crystals of magnetite and/or greigite. We show that in addition to mam genes, there is a conserved set of genes, designated mad genes, specific to the magnetotactic D eltaproteobacteria , some also being present in C andidatus M agnetobacterium bavaricum of the N itrospirae phylum, but absent in the magnetotactic A lphaproteobacteria . Our results suggest that the number of genes associated with magnetotaxis in magnetotactic D eltaproteobacteria is larger than previously thought. We also demonstrate that the minimum set of mam genes necessary for magnetosome formation in M agnetospirillum is also conserved in magnetite‐producing, magnetotactic D eltaproteobacteria . Some putative novel functions of mad genes are discussed.

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