FIG. 4.

Reduction of ferric iron by strain 2-CPC in the presence or absence of AQDS. The reduction of amorphous Fe(III) oxyhydroxide (4 mM) (A) and the reduction of ferric citrate (B) are indicated by the increase in ferric iron concentration. The results are averages of duplicate cultures, with error bars showing the standard deviation. The absence of a bar indicates that the standard deviation was smaller than the symbol. Control A contained iron, acetate, and AQDS, but not biomass; control B contained iron, AQDS, and biomass, but no acetate.