PMC

The catalase and peroxidase activity in the GtoCFEs prepared from aerobically and anaerobically cultivated G. toebii. The breakdown H₂O₂ with aerobically prepared GtoCFE (closed circle) and anaerobically prepared GtoCFE (closed square) was directly monitored at absorbance 240 nm for 120 s under 25°C, respectively. The results represent the mean (± standard deviation) of five independent measurements.

Growth of S. toebii depends on the concentration of GtoCFE. S. toebii was cultivated at various concentrations of GtoCFE in 10 ml PEPN broth at 60°C in an anaerobic jar with a GasPak™ Plus Anaerobic System Envelope for 18 h. The x-axis indicates the final protein concentration of the supplied GtoCFE in the culture broth. S. toebii growth was monitored by nitrite production.

The effect of L-cysteine as a reducing agent on S. toebii growth. L-cysteine (0.025% final concentration) was added to 100 ml PEPN broth containing 0.2 mg ml^-1 of the same CFE prepared from microaerobically, anaerobically or aerobically cultured G. toebii with the experiment of figure 4. S. toebii was cultured in a N₂ gas-flushed anoxic cultivation system at 60°C. Squares, with CFE prepared from aerobically cultured G. toebii; diamonds, with CFE prepared from microaerobically cultured G. toebii; circles, with CFE prepared from anaerobically cultured G. toebii; triangles, without CFE (as a negative control, N.C.). S. toebii growth was monitored by measuring accumulated nitrite in culture broth.

Effects of GtoCFE prepared under various culture conditions on S. toebii growth curves. S. toebii was cultured in a N₂ gas-flushed anoxic cultivation system with 0.2 mg ml^-1 of various GtoCFEs (squares, prepared from aerobic culture; diamonds, prepared from microaerobic culture; circles, prepared from anaerobic culture). Each G. toebii was cultured for overnight under different culture conditions and the cell-free extract was prepared by following the methods section. Nitrite production was used as a measure of S. toebii growth. The G. toebii growth curve (as measured by optical density at 600 nm) under the anaerobic culture condition was shown in the inset.

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).

Growth curve of S. toebii with respect to GtoCFE concentration. One milliliter of anaerobically 12h-cultured S. toebii was inoculated and cultured at 60°C in 100 ml PEPN broth in a N₂ gas-flushed anoxic cultivation system with 0, 10, 20, 50 or 100 μg ml^-1 GtoCFE. The growth of S. toebii was monitored by measuring the optical density at 600 nm (A), concentration of nitrite produced (B) and cell counts (C). Asterisks, without GtoCFE (negative control); circles, 10 μg ml^-1GtoCFE; triangles, 20 μg/ml^-1; diamonds, 50 μg ml^-1; squares, 100 μg ml^-1.