Probing direct cell-to-cell exchange of matter in a Clostridium syntrophic coculture
Abstract
In nature, organisms live in syntrophic communities that divide the metabolic tasks among community members, each according to its metabolic capabilities, but working in complementary ways. There is now accumulating evidence that these syntrophic interactions involve more complex metabolic interactions and transfer of material than previously known. To goal of this project is to dissect a syntrophic co-culture system of Clostridium acetobutylicum, which converts simple and complex carbohydrates into solvents and carboxylates, and the acetogen C. ljungdahlii, which fixes carbon dioxide. It was shown by this lab that direct cell-to-cell interactions and material exchange among the two microbes enabled unforeseen rearrangements in the metabolism of the individual species resulting in the production of non-native metabolites: isopropanol and 2,3-butanediol. This was accomplished by pathway-specific alterations of gene expression, several of which cannot be explained other than by direct exchange of electrons or proteins. Further evidence for direct cell-to-cell interactions was provided using metabolic analysis, fluorescence microscopy (FM) and electron microscopies (TEM & SEM). Specifically, strong evidence was generated for cell-wall and membrane fusion events and exchange of small molecules, reducing equivalents (electrons) and macromolecules. The aim of this project is to expand the investigation of these novel interactions using correlative FM/TEM/SEM and immunogold microscopies to detail the exchange of macromolecules. The project also aims to modify a preliminary protocol in order to probe the direct transfer of plasmid DNA from C. acetobutylicum to C. ljungdahlii. Genetic and culture modifications will be employed to identify mechanism(s) by which C. acetobutylicum transfers reducing equivalent (ÒelectronsÓ) to C. ljungdahlii: if through direct transport of hydrogen or by direct transport of electron-carrier proteins (ferredoxins) or by generating an artificial interspecies electron-transport chain. Using fusions to the novel fluorescent protein tag (FAST), developed and demonstrated in this laboratory for C. acetobutylicum, the project will also investigate proteins that might be involved at the junctions between C. acetobutylicum and C. ljungdahlii aiming to understand mechanisms by which the two organisms exchange proteins. The knowledge developed from this project will form the basis for future developments of syntrophic systems to produce a broad spectrum of metabolites via modular syntrophic co-cultures, involving engineered and non-engineered microorganisms from various genera in addition to Clostridium organisms.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 13, 2019
- Source ID
- W911NF1910274
Entities
People
- Eleftherios T Papoutsakis
Organizations
- Army Contracting Command
- United States Army
- University of Delaware