Figure 7.

Model for synergism between Streptococcus (or other butanediol producers) and Pseudomonas (or other phenazine producers). (a) In low O₂, low pH and quorum sensing conditions, Streptococcus and some other bacteria activate their acetoin metabolism, producing 2,3-butanedione and 2,3-butanediol. This has been shown to elevate phenazine production in P. aeruginosa (Venkataraman et al., 2011). (b) In low O₂, phenazines can act as an alternative electron acceptor, and Fe³⁺ or other electron acceptors could recycle the phenazine redox state in the absence of Oxygen. Blue and white triangles indicate reduced and oxidized phenazine molecules, respectively.