The co-culture of Acidithiobacillus ferrooxidans and Acidiphilium acidophilum enhances the growth, iron oxidation, and CO2 fixation

Although the synergetic interactions between chemolithoautotroph Acidithiobacillus ferrooxidans and heterotroph Acidiphilium acidophilum have drawn a share of attention, the influence of Aph. acidophilum on growth and metabolic functions of At. ferrooxidans is still unknown on transcriptional level. To assess this influence, a co-culture composed by At. ferrooxidans and Aph. acidophilum was successfully acclimated in this study. Depending on the growth dynamics, At. ferrooxidans in co-culture had 2 days longer exponential phase and 5 times more cell number than that in pure culture. The ferrous iron concentration in culture medium and the expression of iron oxidation–related genes revealed that the energy acquisition of At. ferrooxidans in co-culture was more efficient than that in pure culture. Besides, the analysis of CO 2 fixation–related genes in At. ferrooxidans indicated that the second copy of RuBisCO-encoding genes cbbLS - 2 and the positive regulator–encoding gene cbbR were up-regulated in co-culture system. All of these results verified that Aph. acidophilum could heterotrophically grow with At. ferrooxidans and promote the growth of it. By means of activating iron oxidation–related genes and the second set of cbbLS genes in At. ferrooxidans , the Aph. acidophilum facilitated the iron oxidation and CO 2 fixation by At. ferrooxidans .