Reduction of iron oxides and microbial community composition in iron-rich soils with different organic carbon as electron donors

In order to indicate the effect of carbon sources on the composition of dissimilatory iron reducing bacteria (DIRB) and the reduction characteristics of iron oxides in the soils, different carbon sources (glucose, starch, acetate, and plant biomass) were selected and mixed with red soil for anaerobic conservation. During the process, COD, Fe (II), and pH were monitored, and the composition of the microbial community was analyzed. The results show that the amount of reducible ferric iron in red soils differed depending on the carbon source. For example, the amount of reducible ferric iron in the plant biomass system was much higher than in the other three. High throughput sequencing results showed that each system had 1-2 dominant species (operational taxonomy units) with relative abundance ( > 12%) much higher than others. The predominant DIRB in the glucose, starch, and acetic acid systems were the same as found in previous studies. They were Glostridiun species in both glucose and starch systems, and was Geobacter in acetic acid systems. However, the dominant species in the plant biomass system, those belonging to Ignavibacteriaceae, are seldom reported DIRB. Although species from the family were reported to have iron reduction ability, they have never been identified as a dominant group in the iron reduction process before.