| A strain of humic substance- and Fe(Ⅲ)- reducing bacterium was isolated from the subterranean forest sediment and designated as MFC-3. The strain is facultative anaerobic, Gram-negative, motile and rod (1.0-3.0 μm long, 0.5-1.0 μm wide) and identified as Pantoea agglomerans with the 16S rDNA sequence analyses. Batch experiments were conducted to investigate its humic substance-and Fe(Ⅲ)-respiring activity. The results showed that MFC-3 was capable of anaerobic respiration on anthraquinone-2,6-disulphonate (AQDS) as the sole terminal electron acceptor with glucose as the electron donor. Within 48 h, MFC-3 could reduce 0.3 mmol·L-1 AQDS at the expense of 4.5 mmol·L-1 glucose, and the population of bacteria was increased by 7 times. The strain could use sucrose, glucose, citrate, lactate and formate as electron donors for anaerobic respiration, and the reduction rates of AQDS ranked as sucrose (77%)> glucose (66%) > citrate (50%) > lactate (33%) > glycerol (25%)> formate (17%). MFC-3 can also effectively reduce four types of Fe(Ⅲ) oxides. After 25 d, the total Fe(Ⅱ) concentration in the tests of using ferrihydrite,α-FeOOH, γ-FeOOH or α-Fe2O3 as electron acceptor reached 2.5, 2.1, 2.3 and 0.8 mmol·L-1, respectively. As a strain of environmental origin, MFC-3 is quite useful for the study of extracellular respiration and bioremediation of chlorinated organic pollutants in Fe(Ⅲ)/humic substance-rich environments. |
