Taylor D E, Brose E C
Appl Environ Microbiol. 1986 Dec;52(6):1394-7. doi: 10.1128/aem.52.6.1394-1397.1986.
Citrate utilization (Cit+) is encoded by a specific subgroup of incompatibility HI plasmids, viz., IncHI1 plasmids. Only one IncHI1 plasmid, pRG1271, which originated in a Mexican typhoid outbreak in 1972, did not specify Cit+. All other Cit+ plasmids hybridized to a Cit+ probe, a 2-kilobase BglII fragment derived from the Cit+ transposon Tn3411. The position of the Cit+ determinant was mapped to a 13.5-kilobase ApaI fragment within the prototype IncHI1 plasmid R27. No other functions have been mapped within this region. Citrate utilization mediated by IncHI1 was observed only after a prolonged lag period of approximately 150 h, and certain Escherichia coli strains, e.g., E. coli K-12 J53-1, were not able to utilize citrate specified by the H plasmids. Most E. coli strains harboring the multicopy Cit+ plasmid pOH2, a derivative of pBR322, required only 18 to 24 h to express the Cit+ phenotype, but E. coli J53-1 (pOH2) required at least 72 h for expression.
柠檬酸盐利用（Cit+）由不相容性HI质粒的一个特定亚组编码，即IncHI1质粒。只有一个IncHI1质粒，即pRG1271，它起源于1972年墨西哥的伤寒疫情，不具备Cit+功能。所有其他Cit+质粒都与一个Cit+探针杂交，该探针是一个来自Cit+转座子Tn3411的2千碱基BglII片段。Cit+决定簇的位置被定位到原型IncHI1质粒R27内的一个13.5千碱基的ApaI片段上。该区域内尚未定位到其他功能。IncHI1介导的柠檬酸盐利用仅在大约150小时的长时间延迟期后才观察到，并且某些大肠杆菌菌株，例如大肠杆菌K-12 J53-1，无法利用H质粒指定的柠檬酸盐。大多数携带多拷贝Cit+质粒pOH2（pBR322的衍生物）的大肠杆菌菌株只需18至24小时就能表达Cit+表型，但大肠杆菌J53-1（pOH2）至少需要72小时才能表达。
