Dissimilatory Fe(III) reduction characteristics of paddy soil extract cultures treated with glucose or fatty acids.

Dissimilatory Fe(III) reduction is a universal process with irreplaceable biological and environmental importance in anoxic environments. Our knowledge about Fe(III) reduction predominantly comes from pure cultures of dissimilatory Fe(III) reducing bacteria (DFRB). The objective of this study was to compare the effects of glucose and a selection of short organic acids (citrate, succinate, pyruvate, propionate, acetate, and formate) on Fe(III) reduction via the anaerobic culture of three paddy soil solutions with Fe(OH)3 as the sole electron acceptor. The results showed significant differences in Fe(III) reduction among the three paddy soil solutions and substrate types. Bacteria from the Sichuan paddy soil responded quickly to substrate supply and showed higher Fe(III) reducing activity than the other two soil types. Bacteria in the Jiangxi paddy soil culture solution could not use propionate as a source of electrons for Fe(III) reduction. Similarly, bacteria in the Jilin paddy soil culture could not use succinate effectively. Pyruvate was readily used by cultures from all three paddy soil solutions, thus indicating that there were some similarities in substrate utilization by bacteria for Fe(III) reduction. The use of glucose and citrate as substrate for dissimilatory Fe(III) reduction indicates important ecological implications for this type of anoxic respiration.