Mechanistic investigations of the syntrophy between Pseudomonas aeruginosa and 2,3-butanediol fermenters within the context of optimized phenazine-based current generation in bioelectrochemical systems

• Applicant: Professorin Dr. Miriam Agler-Rosenbaum
• Subject Area: Biological Process Engineering ; Microbial Ecology and Applied Microbiology ; Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 250690637

• Final Report Year: 2018

Final Report Abstract

This research project aimed at a mechanistic understanding of the physiological influences that fermenting microorganisms and a small volatile compound (2,3-butanediol) can have on "P. aeruginosa" phenazine production and bioelectrochemcial system (BES) performance. Synergistic microbial co-cultures open completely new possibilities for BES development. This work targeted the detailed investigation of a known BES fermenter (Enterobacter aerogenes) - mediator producer (P. aeruginosa) relationship and wanted to further expand to other 2,3-butandiol (2,3-BD) fermenters in co-culture with P. aeruginosa to obtain a more comprehensive understanding of beneficial and impaired co-culture interactions. In this context, we also evaluated the mediator production, regulation and utilization in P. aeruginosa pure cultures for a general understanding of the mediator physiology. Through very different microbial, molecular, process engineering and omics approaches to our research topic, we strongly increased our understanding and knowledge of phenazine-based microbial extracellular electron transfer in defined microbial co-cultures. We found that the relationship in our model co-culture is not unique and other 2,3-BD fermenters can also synergistically utilize the phenazines, but this synergism seems not only based on 2,3-BD as stimulant. We showed that enhanced long-term performance of our co-cultures is possible through careful process parameter control. On the other hand, we found that the 2,3-BD based synergism seems specific for P. aeruginosa strain PA14, while strain PA01 is generally only little electroactive and the BES isolate KRP1 is generally more electroactive – independent of the carbon source. Therefore, the general regulation of phenazine synthesis became one focus of our work in gene knock-out studies. One of the more difficult experimental parts was the investigation of differential gene expression profiles for two different strains. Generating representative and reproducible biological samples proofed very time consuming. At this point, we are concluding the bioinformatics analysis of differential gene expression, which delivered two gene clusters of interest, which might be involved in phenazine synthesis or function. We also sequenced the small RNAs from all our samples, which will serve as a data pool for subsequent postdoctoral studies. While the extracellular electrochemical properties of the phenazines is fairly well described, little to nothing is known yet about the molecular intracellular action/reaction of the phenazines. We started preliminary work in this direction will continue this work to decipher the intracellular reaction pathway of phenazines. Beyond this, we also transferred phenazine synthesis to Pseudomonas putida to allow for alternative electron discharge in this interesting aerobic biotech host. Several funded projects have already developed in this direction.

Publications

• (2018) Boosting mediated electron transfer in bioelectrochemical systems with tailored defined microbial cocultures. Biotechnology and bioengineering 115 (9) 2183–2193
  Schmitz, Simone; Rosenbaum, Miriam A.
  
• (2016) Strain and Substrate Dependent Redox Mediator and Electricity Production by Pseudomonas aeruginosa. Applied and Environmental Microbiology 82/16, 5026-5038
  Erick M. Bosire, Lars M. Blank, Miriam A. Rosenbaum
  
• (2017) Electrochemical Potential Influences Phenazine Production, Electron Transfer and Consequently Electric Current Generation by Pseudomonas aeruginosa, Frontiers in Microbiology 8, 892
  Erick M. Bosire, Miriam A. Rosenbaum
  
• (2017) Microbial Electrosynthesis I: Pure and Defined Mixed Culture Engineering. In: Advances in Biochemical Engineering/Biotechnology. Springer, Berlin, Heidelberg
  Miriam A. Rosenbaum, Carola Berger, Simone Schmitz, Ronny Uhlig
  
• (2017) Spontaneous Quorum Sensing Mutation Modulates Electroactivity of Pseudomonas aeruginosa PA14, Bioelectrochemistry 117, 1-8
  Carola Berger, Miriam A. Rosenbaum
  
• Carbon source driven virulence factors generation by Pseudomonas aeruginosa, implications for application in bioelectrochemical systems, RWTH Aachen University, 2017
  Erick Maosa Bosire