Mechanisms of microbial magnetite oxidation by Sideroxydans lithotrophicus ES-1

ABSTRACT: Iron-oxidizing bacteria are widely found in natural and man-made environments where they influence varied biogeochemical cycles. Despite their prevalence, the mechanisms and Fe(II) substrates used by these organisms remain understudied. To date, there has been limited exploration of the ability of iron-oxidizing bacteria to utilize solid minerals as electron donors. Sideroxydans lithotrophicus ES-1 is a robust, facultative iron oxidizer with multiple enzymatic pathways for iron oxidation, making it a prime candidate for evaluating extracellular electron uptake mechanisms. In this study, S. lithotrophicus ES-1 was grown on dissolved Fe(II)-citrate and three preparations of magnetite that provided different ratios of soluble and solid Fe(II). S. lithotrophicus ES-1 grew equally well on the different batches of magnetite, suggesting it can adapt to the type of iron present during growth. S. lithotrophicus ES-1 oxidized all available dissolved Fe2+ released from magnetite, and continued to build biomass when only solid Fe(II) remained. Quantitative proteomic analyses of S. lithotrophicus ES-1 grown on these substrates revealed proteome remodeling in response to electron donor and growth state, and uncovered potential proteins and metabolic pathways involved in the oxidation of solid magnetite. While the Cyc2 iron oxidases were highly expressed on both dissolved and solid substrates, the MtoAB complex was only expressed during growth on the solid magnetite, suggesting these proteins play a role in oxidation of solid minerals in S. lithotrophicus ES-1. A set of cupredoxin domain-containing proteins were also identified that were specifically expressed during solid iron oxidation. This work confirmed the iron oxidizer, S. lithotrophicus ES-1, utilized distinct extracellular electron transfer pathways when growing on solid mineral electron donors compared to dissolved Fe(II)-citrate. The presence of multiple pathways, and the ability to regulate their expression and use, could benefit iron-oxidizing bacteria that encounter various electron donors in their environments.

INSTRUMENT(S): Orbitrap Eclipse

ORGANISM(S): Sideroxydans Lithotrophicus (ncbitaxon:63745)

SUBMITTER: CLARA CHAN  

PROVIDER: MSV000093770 | MassIVE | Thu Jan 04 17:44:00 GMT 2024

REPOSITORIES: MassIVE