Straub K L, Hanzlik M, Buchholz-Cleven B E
Max-Planck-Institut für Marine Mikrobiologie, Bremen, Germany.
Syst Appl Microbiol. 1998 Aug;21(3):442-9. doi: 10.1016/S0723-2020(98)80054-4.
Ferric iron was produced anaerobically from ferrous iron through the metabolic activity of recently described ferrous iron-oxidizing, nitrate-reducing bacteria. It was identified as poorly crystallized 2-line ferrihydrite with a particle size of 1-2 nm. This biologically produced ferrihydrite was shown to be a suitable electron acceptor for dissimilatory ferric iron-reducing bacteria in freshwater enrichment cultures, and was completely reduced to the ferrous state; no magnetite formation occurred. Geobacter metallireducens was also able to completely reduce the biologically produced ferrihydrite. These results indicate the possibility of an anaerobic, microbial cycling of iron. Using the biologically produced ferric iron, two isolates of obligately anaerobic, dissimilatory ferric iron-reducing bacteria, strains Dfr1 and Dfr2, were obtained from freshwater enrichment cultures. Analysis of 16S rRNA gene sequences revealed an affiliation with the Geobacter cluster within the family Geobacteraceae. The sequence similarity between strains Dfr1 and Dfr2 is 92.5%. The closest relative of strain Dfr1 is Geobacter sulfurreducens with 92.9%, and of strain Dfr2 Geobacter chapelleii with 93.7% sequence similarity. In addition, strains Dfr1 and Dfr2 are both able to grow by dissimilatory reduction of Mn(IV), S degree, and fumarate. Furthermore, strain Dfr2 is able to reduce akaganeite (beta-FeOOH), a more crystallized type of ferric iron oxide.
通过最近发现的亚铁氧化、硝酸盐还原细菌的代谢活动，亚铁在厌氧条件下被转化为三价铁。所生成的三价铁被鉴定为结晶程度较差的二线水铁矿，粒径为1 - 2纳米。在淡水富集培养物中，这种生物生成的水铁矿被证明是异化铁还原细菌合适的电子受体，并被完全还原为亚铁状态；未形成磁铁矿。地杆菌属还原菌也能够完全还原生物生成的水铁矿。这些结果表明存在铁的厌氧微生物循环的可能性。利用生物生成的三价铁，从淡水富集培养物中获得了两株专性厌氧的异化铁还原细菌菌株Dfr1和Dfr2。对16S rRNA基因序列的分析表明，它们与地杆菌科中的地杆菌簇相关。菌株Dfr1和Dfr2之间的序列相似性为92.5%。菌株Dfr1与硫还原地杆菌的序列相似性最高，为92.9%，菌株Dfr2与查氏地杆菌的序列相似性最高，为93.7%。此外，菌株Dfr1和Dfr2都能够通过异化还原锰（IV）、单质硫和富马酸生长。此外，菌株Dfr2能够还原赤铁矿（β - FeOOH），一种结晶程度更高的三价铁氧化物。
