부산대학교 도서관

In this study, non‐filamentous heterotrophic bacteria with the ability to cause iron precipitation were isolated from water in a ferric ammonium citrate medium. Aerobacter aerogenes was the most common of the organisms found, especially in surface waters. All the bacteria appeared to have two characteristics in common, the ability to utilize citrate as a carbon source and the production of capsular material. Microscopic observations showed a large capsule which appeared to be encrusted with iron. Much of the iron can be removed with the capsule by sonication. In the ferric ammonium citrate medium where the iron is bound with citrate and ammonia, it is hypothesized that this complex material is absorbed into the cell, the carbon from the citrate is utilized, and the remaining iron is absorbed in the capsule. Although different types of organisms were isolated, three cultures were chosen and studied, Aerobacter aerogenes, Serratia indica, and Bacillus pumilus. As in much of the previously reported work, ferric ammonium citrate was used as the organic iron complex. The advantage of this compound is that iron is held in solution under alkaline conditions as high as pH 9.0‐9.5. None of the cultures produced a pH high enough to cause iron precipitation.