Influence of Na + on Synthesis of a Substrate Entry Mechanism in A Marine Bacterium. ∗

Summary

Incubation of resting P. natrie-gens cells in a suspending medium containing 0.26 m Na⁺ and mannitol yielded cells which were able to take up mannitol in media containing a combination of 0.26 m Na⁺ and 0.01 m K⁺, or 0.26 m K⁺, and chlorampheni-col. Cells incubated in media containing a combination of 0.25 m Na⁺ and 0.01 m K⁺, or 0.26 m K⁺ were induced by and took up C¹⁴-labeled mannitol. The uptake in the former medium was partially inhibited by oua-bain and 2,4-DNP whereas that in the latter was unaffected by ouabain and completely suppressed by 2,4-DNP. Although incubation of the cells in 0.26 m K⁺ permitted entry of the substrate mannitol, the need for Na⁺ for growth of the bacteria was not replaced by K⁺. It is suggested that Na⁺ influences synthesis as well as operation of entry mechanism for substrates, whereas a high K⁺ concentration increases rate of diffusion of non-ionizing substrates into marine bacterial cells.