Rogers S R, Anderson J J
J Bacteriol. 1976 Apr;126(1):264-71. doi: 10.1128/jb.126.1.264-271.1976.
Various physiological aspects of the process of iron deposition in Sphaerotilus discophorus were examined to elucidate its role. The values of iron/protein ratios suggested that a direct relationship existed between the iron concentration of the media and the magnitude of final iron deposition. Saturation of the organism's iron deposition system occurred at a 2.0 mM iron concentration, at a value of 0.6 mg of ferric ion per mg of cell protein. Laboratory data indicated that the strain's very low capacity for iron deposition observed at low external iron concentrations makes it unlikely that it is significant in limiting iron in the natural milieu. Under optimal iron concentrations, however, strain SS1 caused precipitation of iron (adsorbed to cellular material) in broth cultures, which was 10 to 100 times that mediated by some "non-iron" microorganisms. The strain's iron requirement, which was found to be between 0.003 and 0.02 mM, is commensurate with that of other microbes. One hundred micrograms of Mn(II) per ml and possibly 10 mug of either Co(II) or Ni(II) per ml could inhibit iron uptake in the deposition system. Sphaerotilus, when tested for its ability to withstand toxic concentrations of certain trace elements (Co, Cu, Mn, Ni, and Cd), demonstrated no exceptional resistance with respect to several other common microorganisms. Final cell yields were not affected by a varying iron concentration for Sphaerotilus growing under conditions of limiting carbon and nitrogen.
为了阐明圆盘球衣菌中铁沉积过程的作用，对该过程的各种生理方面进行了研究。铁/蛋白质比率的值表明，培养基中的铁浓度与最终铁沉积量之间存在直接关系。当铁浓度为2.0 mM（即每毫克细胞蛋白质中含有0.6毫克铁离子）时，生物体的铁沉积系统达到饱和。实验室数据表明，在低外部铁浓度下观察到该菌株的铁沉积能力非常低，这使得它在限制自然环境中的铁含量方面不太可能具有显著意义。然而，在最佳铁浓度下，菌株SS1在肉汤培养物中导致铁（吸附在细胞物质上）沉淀，其沉淀量是一些“非铁”微生物介导沉淀量的10到100倍。该菌株的铁需求量在0.003至0.02 mM之间，与其他微生物的需求量相当。每毫升100微克的Mn(II)以及每毫升可能10微克的Co(II)或Ni(II)可抑制沉积系统中的铁吸收。当测试圆盘球衣菌对某些微量元素（Co、Cu、Mn、Ni和Cd）有毒浓度的耐受能力时，相对于其他几种常见微生物，它没有表现出特殊的抗性。在碳和氮受限的条件下生长时，圆盘球衣菌的最终细胞产量不受铁浓度变化的影响。
