<title>Abstract</title><sec>
<title>Background</title>
Halotolerant Fe (III) oxide reducers affiliated in the family <italic>Desulfuromonadaceae</italic> are ubiquitous and drive the carbon, nitrogen, sulfur and metal cycles in marine subsurface sediment. Due to their possible application in bioremediation and bioelectrochemical engineering, some of phylogenetically close <italic>Desulfuromonas</italic> spp. strains have been isolated through enrichment with crystalline Fe (III) oxide and anode. The strains isolated using electron acceptors with distinct redox potentials may have different abilities, for instance, of extracellular electron transport, surface recognition and colonization. The objective of this study was to identify the different genomic signatures between the crystalline Fe (III) oxide-stimulated strain AOP6 and the anode-stimulated strains WTL and DDH964 by comparative genome analysis.


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<title>Results</title>
The AOP6 genome possessed the flagellar biosynthesis gene cluster, as well as diverse and abundant genes involved in chemotaxis sensory systems and <italic>c</italic>-type cytochromes capable of reduction of electron acceptors with low redox potentials. The WTL and DDH964 genomes lacked the flagellar biosynthesis cluster and exhibited a massive expansion of transposable gene elements that might mediate genome rearrangement, while they were deficient in some of the chemotaxis and cytochrome genes and included the genes for oxygen resistance.


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<title>Conclusions</title>
Our results revealed the genomic signatures distinctive for the ferric iron oxide- and anode-stimulated <italic>Desulfuromonas</italic> spp. strains. These findings highlighted the different metabolic abilities, such as extracellular electron transfer and environmental stress resistance, of these phylogenetically close bacterial strains, casting light on genome evolution of the subsurface Fe (III) oxide reducers.


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