Comparison of S. toebii growth curves and dependence on cell-free extracts from various G. toebii growth stages. S. toebii was inoculated and cultured at 60°C in 100 ml PEPN broth under anaerobic conditions with 200 μg ml-1 GtoCFE prepared from various G. toebii growth stages. G. toebii was cultured for 2 h (lag phase, squares), 9 h (exponential phase, circles) and 24 h (stationary phase, triangles), and then CFEs were prepared. The G. toebii growth curve (as measured by optical density at 600 nm) is shown in the inset (panel A). S. toebii growth was monitored by nitrite production (A) and optical density at 600 nm (B).