SUMMARY: Parameters of cellular energetics (ATP pools, adenylate energy charge, GTP pools and oxygen consumption) as well as bioluminescence and growth have been examined in batch cultures of four different species of luminous bacteria. The findings indicate that all of these energetic parameters remain constant throughout the growth cycle while bioluminescence is induced and increases many fold. These observations hold true for very bright strains during their dim and bright phases of growth, as well as for a luminescence-conditional strain under bright or dark conditions. The percentage of the total oxygen consumption that was due to bioluminescence was shown to vary by as much as a factor of 10 during growth. For very bright cells, the oxygen consumption experiments suggest both that the energetic requirements of the bioluminescent system are significant, and that the quantum efficiency ( ) of the luciferase is quite high, possibly approaching 1·0. Similar considerations based on ATP pool size and energetic estimates of luminescence indicate that the luminous system in bright cells represents a small but possibly significant energy drain. Finally, two methodological features are discussed. First, it was shown that extracts of cells that have been grown in media devoid of inorganic phosphate contain a heat-stable ATPase activity, which can lead to falsely low ATP values. Second, it was shown that the interfering effect of GTP on the assay of ATP could be completely overcome by the addition of GDP to the assay mixture.


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