['To determine the effects of anaerobic electron acceptors on 3-methylindole (3-MI) and 4-methylphenol (4-MP) production in swine lagoon enrichments and Clostridium scatologenes ATCC 25775.', 'Swine lagoon sediment was incubated anaerobically in tryptone-yeast extract medium with (10 mmol l(-1)) Na(2)SO(4), KNO(3), dimethyl sulfoxide or Fe(III). With Fe(III), 3-MI and 4-MP levels increased significantly to 138 +/- 15.8 and 187 +/- 14.0 micromol l(-1), respectively. Clostridium scatologenes cultured in brain-heart infusion medium amended with (10 mmol l(-1)) Na(2)SO(4), KNO(3), MnO(2) or Fe(III), resulted in only Fe(III) significantly increasing 3-MI (1308 micromol l(-1)) and 4-MP (367 micromol l(-1)) levels. In semi-defined medium, Fe(III) alone and Fe(III) + L-tryptophan (1 mmol l(-1)) resulted in a 1.85-fold and 15.6-fold increase in 3-MI levels over L-tryptophan alone, respectively. Fe(III) alone and Fe(III) + L-tyrosine (1 mmol l(-1)) caused a 4.4-fold and 22.9-fold increase in 4-MP levels over tyrosine alone, respectively. Fe(III) did not increase growth of Cl. scatologenes.'] Does fe ( III ) stimulate 3-methylindole and 4-methylphenol production in swine lagoon enrichments and Clostridium scatologenes ATCC 25775?