Wang C C, Newton A
J Bacteriol. 1969 Jun;98(3):1142-50. doi: 10.1128/jb.98.3.1142-1150.1969.
Escherichia coli strains B/r and 2276 contain an active transport system for iron. The system is energy-dependent, repressed by excess iron in the growth medium, and capable of accumulating iron inside of the cells at concentrations 2,000-fold higher than those in the medium. Two tonB-trp deletion mutants, strains B/rlt and B/lt7, which are sensitive to chromic ion and require high levels of iron for normal growth, are deficient in this active transport system. A point mutant, strain Chr2, which is also sensitive to chromic ion and requires high levels of iron for growth, has the active uptake system but cannot synthesize a specific chelator for iron, 2,3-dihydroxybenzoylserine (DHBS). Evidence is presented to support the hypothesis that both the active uptake system and chelation of iron by DHBS play a role in iron uptake from iron-deficient medium. The chromium sensitivity of the mutants can be explained by inhibition of uptake of exogenous iron.
大肠杆菌菌株B/r和2276含有一种铁的主动运输系统。该系统依赖能量，受生长培养基中过量铁的抑制，能够在细胞内积累铁，其浓度比培养基中的浓度高2000倍。两个tonB-trp缺失突变体，即对铬离子敏感且正常生长需要高水平铁的菌株B/rlt和B/lt7，在这种主动运输系统中存在缺陷。一个点突变体，即对铬离子也敏感且生长需要高水平铁的菌株Chr2，具有主动摄取系统，但不能合成一种特定的铁螯合剂，即2,3-二羟基苯甲酰丝氨酸（DHBS）。有证据支持这样的假设，即主动摄取系统和DHBS对铁的螯合作用在从缺铁培养基中摄取铁的过程中都发挥了作用。突变体对铬的敏感性可以通过抑制外源铁的摄取来解释。
