Perturbations in the Proteome of Shewanella oneidenis Exudates in Response to the Presence of Se(IV) During Cell Growth and Exudate Production

In this study, we examine changes in the exuded proteome of Shewanella oneidensis cells caused by incubation of the cells in the presence of aqueous Se(IV). Se(IV) reduction by S. oneidensis exudates is inducible by exposure of the cells to Se(IV) during growth and exudate production, but can be stopped when exudate sulfhydryl sites are blocked. Therefore, determining the redox-active proteins that are up-regulated under these conditions and that contain sulfhydryl active binding sites constrains which proteins are responsible for the Se(IV) reduction. Bottom-up proteomics was used to quantify the protein composition of bacterial exudates produced by S. oneidensis cells both with and without exposure to Se(IV) during growth and exudate production. 955 proteins were identified within the exudates, of which 144 proteins were differentially expressed in response to Se(IV) exposure (54 up-regulated, 90 down-regulated). We identify 2 of the 54 up-regulated proteins that are known to possess redox activity against Se(IV) and also contain a sulfhydryl site within or proximal to the active site: AhpF and Sye4. These results expand our understanding of the impact of heavy metal exposure on bacterial metabolism and identify key proteins for further study toward optimization of microbial remediation of selenium-contaminated waters.