Wang C C, Newton A
J Bacteriol. 1969 Jun;98(3):1135-41. doi: 10.1128/jb.98.3.1135-1141.1969.
Utilization of iron (Fe(3+)) by Escherichia coli depends upon a system which is determined by at least two genetic loci. Mutants which carry a deletion of the tonB-trp region of the chromosome grow only when very high concentrations of iron are present in the medium. These strains are sensitive to chromic ion (Cr(3+)) and, unlike the parent strain, fail to grow on MnSO(4) when FeSO(4) is not added to the medium. A second type of mutant, Chr2, which was isolated on the basis of its sensitivity to chromic ion, also requires a high concentration of iron for growth. This mutant can be distinguished phenotypically from the deletion mutants since it grows normally on low concentrations of iron, provided citrate is added to the medium. The chromium sensitivity of both types of mutants can be reversed by high concentrations of exogenous iron. The data are interpreted to indicate that the E. coli mutants studied are defective in iron transport and that residual iron transport is in some way inhibited by chromic ion.
大肠杆菌对铁（Fe(3+)）的利用依赖于一个由至少两个基因位点决定的系统。携带染色体tonB - trp区域缺失的突变体只有在培养基中存在非常高浓度的铁时才能生长。这些菌株对铬离子（Cr(3+)）敏感，并且与亲本菌株不同，当培养基中不添加FeSO(4)时，它们在MnSO(4)上无法生长。第二种类型的突变体Chr2，是根据其对铬离子的敏感性分离出来的，它生长也需要高浓度的铁。这种突变体在表型上可以与缺失突变体区分开来，因为如果向培养基中添加柠檬酸盐，它在低浓度的铁上能正常生长。两种类型突变体的铬敏感性都可以被高浓度的外源铁逆转。这些数据被解释为表明所研究的大肠杆菌突变体在铁转运方面存在缺陷，并且残余的铁转运在某种程度上受到铬离子的抑制。
