Pyruvate Accelerates Palladium Reduction by Regulating Catabolism and the Electron Transfer Pathway in Shewanella oneidensis

Abstract

Shewanella oneidensis is a model strain of the electrochemical active bacteria (EAB) because of its strong capability of extracellular electron transfer (EET) and genetic tractability. In this study, we investigated the effect of carbon sources on EET in S. oneidensis by using reduction of palladium ions (Pd(II)) as a model and found that pyruvate greatly accelerated the Pd(II) reduction compared with lactate by resting cells. Both Mtr pathway and hydrogenases played a role in Pd(II) reduction when pyruvate was used as a carbon source. Furthermore, in comparison with lactate-feeding S. oneidensis, the transcriptional levels of formate dehydrogenases involving in pyruvate catabolism, Mtr pathway, and hydrogenases in pyruvate-feeding S. oneidensis were up-regulated. Mechanistically, the enhancement of electron generation from pyruvate catabolism and electron transfer to Pd(II) explains the pyruvate effect on Pd(II) reduction. Interestingly, a 2-h time window is required for pyruvate to regulate transcription of these genes and profoundly improve Pd(II) reduction capability, suggesting a hierarchical regulation for pyruvate sensing and response in S. oneidensis. IMPORTANCE The unique respiration of EET is crucial for the biogeochemical cycling of metal elements and diverse applications of EAB. Although a carbon source is a determinant factor of bacterial metabolism, the research into the regulation of carbon source on EET is rare. In this work, we reported the pyruvate-specific regulation and improvement of EET in S. oneidensis and revealed the underlying mechanism, which suggests potential targets to engineer and improve the EET efficiency of this bacterium. This study sheds light on the regulatory role of carbon sources in anaerobic respiration in EAB, providing a way to regulate EET for diverse applications from a novel perspective.

Cytochrome P450-mediated co-metabolism of fluoroquinolones by Haematococcus lacustris for simultaneously promoting astaxanthin and lipid accumulation

“…S3). Based on these results, it was speculated that the external carbon source activated microalgae to form products from glycerol metabolisms, such as pyruvate, which is a key component in synergistic metabolism and an excellent electron donor for biodegrading antibiotics [29].…”

YgfY Contributes to Stress Tolerance in Shewanella oneidensis Neither as an Antitoxin Nor as a Flavinylation Factor of Succinate Dehydrogenase

“…To detect the transcription capability, a method of click chemistry using 5-ethynyluridine and an azide-modified fluorophore was adopted [10]. Overnight cultures of WT and ∆ygfY were diluted into fresh LB to 0.01 of OD 600 , and then cultured at 30 • C for 3 h. Then, cultures were collected, concentrated for 25 folds, and added with EU (Molecular Probes, Inc., Eugene, OR, USA) to a final concentration of 0.5 mM.…”

“…The transcription capability of ∆ygfY was compared with WT using EU-based click chemistry [10]. EU is an uracil analog, and is incorporated into nascent RNA after addition.…”

“…The decreased transcription of ribosome proteins in ΔygfY is consistent with growth defect of this mutant. The transcription capability of ΔygfY was compared with WT using EU-based click chemistry [10]. EU is an uracil analog, and is incorporated into nascent RNA after addition.…”

“…SdhE, a CptB(YgfY) homolog in Serratia sp. and Acetobacter pasteurianus, works as a flavinylation factor of succinate dehydrogenase (SDH) [9,10]. SdhE is even involved in flavinylation of fumarate reductase in Serratia sp., demonstrating the broadness of the target list of CptB/YgfY/SdhE [11].…”