Abstract
Effects of monovalent cations on luminescence and respiratory activity were studied in the marine luminous bacterium Vibrio harveyi. Maximum oxygen uptake was observed in the presence of Na+over the pH range tested (6.5–8.5). At alkaline pH, effects of monovalent cation on luminescence were similar to those on the oxygen uptake. Although KCN addition caused a marked increase in luminescence, the enhanced luminescence with Na+was still greater than that with Li+. However, at acidic pH, K+increases luminescence more than Na+does. These results indicate that there is not only a competitive but also a cooperative relationship between luminescence and respiration. The respiratory NADH oxidase in the membrane fraction of V. harveyi showed some distinctive characters which are unique to the respiratory-dependent primary Na+pump, suggesting the possibility of coupling between the Na+pump and the luciferase system. This was also supported by the results from CCCP-resistant growth and luminescence at alkaline pH. The coupling mechanisms between luminescence and respiration in V. harveyi are discussed.