Dissimilatory iron-reducing microorganisms: The phylogeny, physiology, applications and outlook

Abstract

Dissimilatory iron reduction (DIR) is an important form of microbial respirations and a key part of iron biogeochemical cycle. A wide range of both bacteria and archaea that can conserve energy through Fe(III) reduction are called dissimilatory iron-reducing microorganisms (DIRMs). They have been increasingly recognized as important for coupling organic carbon oxidation in diverse anaerobic environments, such as soil, sediments, freshwater, marine water as well as extreme environments. In parallel with their phylogenetic diversity, DIRMs possess metabolic versatility, including multiple extracellular electron transfer (EET) pathways and various electron donors as well as acceptors. In this review, phylogenetic, environmental distribution of DIRMs was demonstrated comprehensively by summarizing 51 isolated DIRMs belonging to 27 genera in previous literature. EET mechanisms were further elaborated on based on four DIRMs representatives: Geobacter, Shewanella, Gram-positive bacteria and archaea. Various electron donors, acceptors, and novel metabolisms revealed recently prompt the development of DIRMs biotechnological applications, including bioleaching, bioremediation, biosynthesis, anaerobic fermentation, and production of bioelectricity. Although past decades have witnessed a great increase of the publications in DIRMs, further investigation are required for deep understanding and practical applications, such as their roles in natural environments, EET mechanisms in different DIRMs, cooperation with other microbes, and mechanisms of improved bioproduction by adding iron-oxides.

GRAPHICAL ABSTRACT

DIRMs in real world. (1) they can be used for bioleaching; (2) they can be used for bioremediation for heavy metals and organic pollutants; (3) in aquatic environments, they can conduct iron reduction and form iron precipitate; (4) they can be used to produce current; (5) they can synthesize bioproducts; (6) they can form stable network with other soil microorganisms; (7) in various environments, they can form microbial iron cycle with iron-oxidizing microorganisms and influence many processes.

Keywords:

• dissimilatory iron-reducing microorganisms
• extracellular electron transfer
• Geobacter
• Shewanella
• bioremediation
• biosynthesis

HANDLING EDITORS:

• Hyunjung ‘Nick’ Kim

Acknowledgements

We also thank the Earth Microbiome Project (EMP, www.earthmicrobiome.org), where we obtained the distribution data of common DIRMs genera. Sample processing, sequencing, and core amplicon data analysis were performed by the EMP, and all amplicon sequence data and metadata have been made public through the EMP data portal (qiita.microbio.me/emp).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Key Research and Development Program-of China under Grant (No. 2020YFC1808801).