Abstract

Shewanella putrefaciens IR-1 and MR-1 were cultivated by using various combinations of electron donor-acceptor, lactate-Fe(III), lactate-nitrate, pyruvate-Fe(III), pyruvate-nitrate, H_2 -acetate-Fe(III) and H_2 -acetate-nitrate. Both strains grew fermentatively on pyruvate but not on lactate without an electron acceptor. In culture with Fe(III), both strains grew on pyruvate and lactate but not on H_2 -acetate-CO_2 . In cultivation with nitrate, both strains grew on pyruvate, lactate and on H_2 -acetate-CO_2 . The growth yields of IR-1 on pyruvate, pyruvate-Fe(III) and lactate-Fe(III) were about 3.4, 3.5, and 3.6 (g cell/M substrate), respectively, but the yields on lactate-nitrate, pyruvate-nitrate and H_2 -acetate-CO_2 ?trate were about 6.8, 5.9, and 9.4 (g cell/M substrate), respectively. From the growth properties of both strains on media with Fe(III) as an electron acceptor, the bacterial growth was confirmed not to be increased by addition of Fe(III) as an electron acceptor to the growth medium, which indicates a possibility that the dissimilatory reduction of Fe(III) to Fe(II) may not be coupled to free energy production.

• Keywords: anaerobic respiration; electron sink; iron-reducing bacterium; growth yield; Shewanella putrefaciens