Core Transcriptome of Hydrogen Producing Marine Vibrios Reveals Contribution of Glycolysis in Their Efficient...

Pyruvate (Pyr) is the end product of the glycolysis pathway. Pyr is also renewable and is further metabolized to produce formate, which is the precursor of H₂, via pyruvate formate lyase (PFL) under anaerobic conditions. The formate is excluded and re-imported via the formate channel and is then converted to H₂ via the formate hydrogenlyase (FHL) complex. In H₂ producing marine vibrios, such as Vibrio tritonius and Vibrio porteresiae in the Porteresiae clade of the family Vibrionaceae, apparent but inefficient H₂ production from Pyr has been observed. To elucidate the molecular mechanism of why this inefficient H₂ production is observed in Pry-metabolized marine vibrio cells and how glycolysis affects those H₂ productions of marine vibrios, the "Core Transcriptome" approach to find common gene expressions of those two major H₂ producing Vibrio species in Pyr metabolism was first applied. In the Pyr-metabolized vibrio cells, genes for the "Phosphoenolpyruvate (PEP)-Pyruvate-Oxalate (PPO)" node, due to energy saving, and PhoB-, RhaR-, and DeoR-regulons were regulated. Interestingly, a gene responsible for oxalate/formate family antiporter was up-regulated in Pyr-metabolized cells compared to those of Glc-metabolized cells, which provides new insights into the uses of alternative formate exclusion mechanics due to energy deficiencies in Pyr-metabolized marine vibrios cells. We further discuss the contribution of the Embden-Meyerhof-Parnas (EMP) pathway to efficient H₂ production in marine vibrios.