What is the most likely effect of adding a sodium ionophore to a culture of V. cholerae?

• A. Increased ATP production
• B. Decreased production of ATP
• C. Increased cell membrane permeability
• D. Enhanced growth rate

Answer: (B)

Adding a sodium ionophore to a culture of V. cholerae would lead to a decreased production of ATP. Sodium ionophores facilitate the transport of sodium ions across the cell membrane, which disrupts the electrochemical gradient that is vital for ATP synthesis in bacteria.

In prokaryotes like V. cholerae, ATP production is heavily reliant on the establishment of a proton motive force (PMF) across the inner membrane, generated by the electron transport chain during cellular respiration. This PMF is essential for the functioning of ATP synthase, the enzyme responsible for synthesizing ATP from ADP and inorganic phosphate. When a sodium ionophore allows unregulated sodium ions to flow into or out of the cell, it dissipates the electrochemical gradient, disrupting the PMF and ultimately leading to reduced ATP synthesis.

It's important to note that while increasing cell membrane permeability is a characteristic of sodium ionophores, the most significant biological consequence in this situation is the impact on ATP production, which directly relates to cellular energy levels and metabolic functions. Enhanced growth rate and increased ATP production would not occur because the cells would be starved of the necessary energy to sustain these processes.