The Relationship between Energy-dependent Phagocytosis and the Rate of Oxygen Consumption in Tetrahymena

This study investigated the relationship between phagocytosis and cellular respiration in Tetrahymena pyriformis, a ciliate protozoan. Researchers exposed cells to carmine particles and measured oxygen uptake using Warburg manometry. When exponentially growing cells ingested particles into food vacuoles, oxygen consumption increased by 17%, while starving cells showed a more dramatic 47.5% increase. Using a temperature-sensitive mutant that cannot form food vacuoles at 37°C, the authors confirmed that the respiratory increase required actual particle ingestion rather than just particle presence. Heat-synchronized cells showed decreased respiration during cell division when food vacuole formation normally ceases. Chemical inhibitors demonstrated a direct correlation: dimethyl sulfoxide (DMSO) dose-dependently suppressed both food vacuole formation and respiration to starvation levels, while cytochalasin B unexpectedly had minimal respiratory effects despite blocking vacuole completion. The authors calculated that exponentially growing cells expend approximately 6×10⁻¹³ mol ATP per food vacuole formed, similar to energy costs in mammalian phagocytes. These results establish a strong metabolic coupling between phagocytosis and oxidative metabolism in Tetrahymena.

Key findings

• Phagocytosis increases oxygen consumption by 17% in growing cells and 47.5% in starved Tetrahymena pyriformis cells within the first 20 minutes of particle exposure
• Temperature-sensitive mutant experiments prove the respiratory increase depends on actual particle ingestion into food vacuoles, not merely particle presence in the medium
• Dimethyl sulfoxide (DMSO) dose-dependently inhibits both food vacuole formation and cellular respiration, reducing oxygen uptake to starvation-level rates
• Heat-synchronized cells show decreased respiration specifically during cell division when food vacuole formation ceases, supporting the metabolic coupling
• Approximately 6×10⁻¹³ mol ATP is required per food vacuole formed, a metabolic cost comparable to phagocytosis in mammalian immune cells