Question

7. What is so unusual about the electron acceptors that Shewanella a ron acceptors that Shewanella and Geobacter species ke them interesting organisms for bioenergy studies?

Answer 1

1. Shewanalla and geobactor species are model organisms that enables the dissimilatory reduction of extracellular electron acceptors. Both the organisms uses c- cytochromes as essential electron transferring proteins.

2. The first respiratory processes that were discovered that was dependent on electron transfer to cell surface was the shewanella and geobacter species using iron and manganese respiration. Fe(III) reducing bacteria geobacter mettalireducens and shewanella oneidensis which conserves their energy for their anaerobic growth through the reduction U($\vee$I)

3. Shewanella species isolated from lake oneida sediments while oxidising succinate and reducing manganese oxide. Geobacter species were isolated from potomac river sediments while oxidising acetate and reducing iron oxide. These bacteria are gram negative and contains 2 lipid bilayers surrounding the cell.

4. One of the findings in research was the pink color in their microbial colonies same has Hb in our rbc's that contain heme containing cytochrome proteins and hence cytochromes present in these bacteria are involved in transferring electrons from inner membrane across their periplasm and to the outer membrane to reduce extracellular electron acceptor.

5. shewanella uses to reach electron acceptors using outer membrane vesicles that are linked to outer membrane extensions and these extensions are filled with cytochromes full of electrons and they gets delivered to the extracellular acceptor. These species interact with environment by retracting their extensions from cell to interact with extracellular e- acceptor.

6. In case of Geobacter species instead of extensions they uses conductive protein filaments. They are seen as pili and involves in DNA uptake, adhesion, motility etc..

7. The diversity of their EET mechanisms are unique because their evolution happened under unique selective pressures. And both of the species reside in different environmental niches.

8. Applications of EET includes in bioremediation and sensing of toxic minerals such as uranium, arsenic and chromium. Replacing mineral oxides with electrode creates good amounts of electricity and used to power deep sea devices. Bioenergy can be produced as a byproduct in wastewater treatment.

Geobacter spp. Shewanella spp. Natural Environment Anaerobic Sediments FeCul Rich Marine & Freshwater Sediments Phylogeny J-Proteobacteria Y- Protesbacteria Pathway Multiple Pathways - Extracellular e acceptor. Conserved single pathway to reduce all extra-cellular e-acceptors: Single Biofilms on Electrodes layer Multilayerd & Active 10 m away from e-acceptor of cells © Shuttle Production soluble Cyto chrome FON, Redox active molecule - ② Celular Extensions é pilli/ cytochrome charms membrane extensions :