Abstract:Shewanella oneidensis strain MR-1 is a facultative anaerobe that thrives in redox-stratified environments due to its ability to utilize a wide array of terminal electron acceptors. Conversely, the electron donors utilized by S. oneidensis are more limited and include products of primary fermentation such as lactate, pyruvate, formate, and hydrogen. Lactate, pyruvate, and hydrogen metabolisms in S. oneidensis have been described previously, but little is known about the role of formate oxidation in the ecophysi… Show more
“…4). Using GlcNac and lactate as sole carbon sources and fumarate as the sole electron acceptor, the biomass production and reaction flux distributions of the WP3 wild-type and mutant models revealed that substrate-level phosphorylation was the primary source of anaerobic energy conservation, a trait that has been noted in MR-1 (8, 10). This indicates that the primary usage of substrate-level phosphorylation could be a conserved feature in the anaerobic respiration of both group 1 and group 2 species and suggests that this feature could have evolved during the early differentiation of Shewanella .…”
Section: Discussionmentioning
confidence: 92%
“…Several recent studies have focused on identifying the relative contributions of two distinct ATP-producing mechanisms (8–10), oxidative phosphorylation and substrate-level phosphorylation. Oxidative phosphorylation is typically associated with respiration, where the reduction of terminal electron acceptors is coupled to proton motive force (PMF) generation, and the PMF subsequently contributes to ATP synthesis via ATP synthase (ATPase).…”
The well-studied nature of the metabolic diversity of Shewanella bacteria makes species from this genus a promising platform for investigating the evolution of carbon metabolism and energy conservation. The Shewanella phylogeny is diverged into two major branches, referred to as group 1 and group 2. While the genotype-phenotype connections of group 2 species have been extensively studied with metabolic modeling, a genome-scale model has been missing for the group 1 species. The metabolic reconstruction of Shewanella piezotolerans strain WP3 represented the first model for Shewanella group 1 and the first model among piezotolerant and psychrotolerant deep-sea bacteria. The model brought insights into the mechanisms of energy conservation in WP3 under anaerobic conditions and highlighted its metabolic flexibility in using diverse carbon sources. Overall, the model opens up new opportunities for investigating energy conservation and metabolic adaptation, and it provides a prototype for systems-level modeling of other deep-sea microorganisms.
“…4). Using GlcNac and lactate as sole carbon sources and fumarate as the sole electron acceptor, the biomass production and reaction flux distributions of the WP3 wild-type and mutant models revealed that substrate-level phosphorylation was the primary source of anaerobic energy conservation, a trait that has been noted in MR-1 (8, 10). This indicates that the primary usage of substrate-level phosphorylation could be a conserved feature in the anaerobic respiration of both group 1 and group 2 species and suggests that this feature could have evolved during the early differentiation of Shewanella .…”
Section: Discussionmentioning
confidence: 92%
“…Several recent studies have focused on identifying the relative contributions of two distinct ATP-producing mechanisms (8–10), oxidative phosphorylation and substrate-level phosphorylation. Oxidative phosphorylation is typically associated with respiration, where the reduction of terminal electron acceptors is coupled to proton motive force (PMF) generation, and the PMF subsequently contributes to ATP synthesis via ATP synthase (ATPase).…”
The well-studied nature of the metabolic diversity of Shewanella bacteria makes species from this genus a promising platform for investigating the evolution of carbon metabolism and energy conservation. The Shewanella phylogeny is diverged into two major branches, referred to as group 1 and group 2. While the genotype-phenotype connections of group 2 species have been extensively studied with metabolic modeling, a genome-scale model has been missing for the group 1 species. The metabolic reconstruction of Shewanella piezotolerans strain WP3 represented the first model for Shewanella group 1 and the first model among piezotolerant and psychrotolerant deep-sea bacteria. The model brought insights into the mechanisms of energy conservation in WP3 under anaerobic conditions and highlighted its metabolic flexibility in using diverse carbon sources. Overall, the model opens up new opportunities for investigating energy conservation and metabolic adaptation, and it provides a prototype for systems-level modeling of other deep-sea microorganisms.
“…Similar to S. oneidensis , Ca . Brocadia electricigens gets a significant amount of proton motive force and feeds the quinol pool in the inner membrane by transporting and oxidizing formate in the periplasm ( 85 ) (Fig. S10).…”
AbstractAnaerobic ammonium oxidation (anammox) by anammox bacteria contributes significantly to the global nitrogen cycle, and plays a major role in sustainable wastewater treatment. Anammox bacteria convert ammonium (NH4+) to dinitrogen gas (N2) using nitrite (NO2−) or nitric oxide (NO) as the electron acceptor. In the absence of NO2− or NO, anammox bacteria can couple formate oxidation to the reduction of metal oxides such as Fe(III) or Mn(IV). Their genomes contain homologs of Geobacter and Shewanella cytochromes involved in extracellular electron transfer (EET). However, it is still unknown whether anammox bacteria have EET capability and can couple the oxidation of NH4+ with transfer of electrons to carbon-based insoluble extracellular electron acceptors. Here we show using complementary approaches that in the absence of NO2−, freshwater and marine anammox bacteria couple the oxidation of NH4+ with transfer of electrons to carbon-based insoluble extracellular electron acceptors such as graphene oxide (GO) or electrodes poised at a certain potential in microbial electrolysis cells (MECs). Metagenomics, fluorescence in-situ hybridization and electrochemical analyses coupled with MEC performance confirmed that anammox electrode biofilms were responsible for current generation through EET-dependent oxidation of NH4+. 15N-labelling experiments revealed the molecular mechanism of the EET-dependent anammox process. NH4+ was oxidized to N2 via hydroxylamine (NH2OH) as intermediate when electrode was the terminal electron acceptor. Comparative transcriptomics analysis supported isotope labelling experiments and revealed an alternative pathway for NH4+ oxidation coupled to EET when electrode is used as electron acceptor compared to NO2−as electron acceptor. To our knowledge, our results provide the first experimental evidence that marine and freshwater anammox bacteria can couple NH4+ oxidation with EET, which is a significant finding, and challenges our perception of a key player of anaerobic oxidation of NH4+ in natural environments and engineered systems.
“…1A, indicating the reduction of metal ions into (a) Pd and (b) Au NPs by the bacteria. 14,15 As measured at 600 nm, the light-scattering intensity of a single cell increased strongly after incubation in the suspensions, including the palladium ion, and became constant after 1 h (Fig. 1B).…”
A simple method for the detection of metal ions in solution is proposed, using Shewanella oneidensis, which has the ability to reduce metal ions into metal nanoparticles on the cell surface. The method can be used to identify metal ions in solution using the light-scattering characteristics of the metal nanoparticles formed on the cells.
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