Advertisement

Redox homeostasis phenotypes in RubisCO-deficient Rhodobacter sphaeroides via ensemble modeling

Authors

  • Matthew L. Rizk,

    1. Dept. of Chemical and Biomolecular Engineering, University of California, Los Angeles, 5531 Boelter Hall, Los Angeles, CA 90095
    Search for more papers by this author
  • Rick Laguna,

    1. Dept. of Microbiology, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210
    Search for more papers by this author
  • Kevin M. Smith,

    1. Dept. of Chemical and Biomolecular Engineering, University of California, Los Angeles, 5531 Boelter Hall, Los Angeles, CA 90095
    Search for more papers by this author
  • F. Robert Tabita,

    1. Dept. of Microbiology and Plant Molecular Biology/Biotechnology Program, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210
    Search for more papers by this author
  • James C. Liao

    Corresponding author
    1. Dept. of Chemical and Biomolecular Engineering, University of California, Los Angeles, 5531 Boelter Hall, Los Angeles, CA 90095
    • Dept. of Chemical and Biomolecular Engineering, University of California, Los Angeles, 5531 Boelter Hall, Los Angeles, CA 90095
    Search for more papers by this author

Abstract

Photosynthetic bacteria are capable of carrying out the fundamental biological processes of carbon dioxide assimilation and photosynthesis. In this work, ensemble modeling (EM) was used to examine the behavior of mutant strains of the nonsulfur purple photosynthetic bacterium Rhodobacter sphaeroides containing a blockage in the primary CO2 assimilatory pathway, which is responsible for cellular redox balance. When the Calvin–Benson–Bassham (CBB) pathway is nonfunctional, spontaneous adaptive mutations have evolved allowing for the use of at least two separate alternative redox balancing routes enabling photoheterotrophic growth to occur. The first of these routes expresses the nitrogenase complex, even in the presence of normal repressing ammonia levels, dissipating excess reducing power via its inherent hydrogenase activity to produce large quantities of hydrogen gas. The second of these routes may dissipate excess reducing power through reduction of sulfate by the formation of hydrogen sulfide. EM was used here to investigate metabolism of R. sphaeroides and clearly shows that inactivation of the CBB pathway affects the organism's ability to achieve redox balance, which can be restored via the above-mentioned alternative redox routes. This work demonstrates that R. sphaeroides is capable of adapting alternative ways via mutation to dissipate excess reducing power when the CBB pathway is inactive, and that EM is successful in describing this behavior. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2011

Ancillary