Valentine P J, Shoemaker N B, Salyers A A
Department of Microbiology, University of Illinois, Urbana 61801.
J Bacteriol. 1988 Mar;170(3):1319-24. doi: 10.1128/jb.170.3.1319-1324.1988.
A 4.2-kilobase cryptic Bacteroides plasmid, pB8-51, is found in several colonic Bacteroides species. To determine whether pB8-51 is mobilized by any of the known Bacteroides conjugal elements, we constructed an Escherichia coli-Bacteroides shuttle vector, pVAL-1, which contains pB8-51. We constructed Bacteroides uniformis 0061 derivatives which carry pVAL-1 and various Bacteroides conjugal elements. The Bacteroides conjugal elements tested were six conjugal tetracycline resistance (Tcr) elements (which appear to be chromosomal), i.e., Tcr ERL, Tcr V479, Tcr Emr ERL, Tcr Emr 12256, Tcr Emr DOT, and Tcr Emr CEST, and the conjugal erythromycin resistance (Emr) plasmid pBF4. These Tcr conjugal elements have not been extensively characterized, except for Tcr ERL. All six Tcr elements tested mobilized pVAL-1 at high frequency (10(-3) to 10(-5)) from one Bacteroides strain to another or from a Bacteroides strain to E. coli. Pregrowth of the donors (containing one of the Tcr elements and pVAL-1) in 1 microgram of tetracycline per ml enhanced the transfer of pVAL-1 by 20- to 10,000-fold, depending on which Tcr element was present in the donor. An Ems derivative of pBF4 (pBF4 delta E2) mobilized pVAL-1 from one Bacteroides strain to another at a frequency of 10(-4) but did not mobilize pVAL-1 from a Bacteroides strain to E. coli as efficiently. Thus the Tcr conjugal elements and pBF4 recognize a mobilization region on pB8-51.
一种4.2千碱基的隐秘拟杆菌属质粒pB8 - 51存在于多种结肠拟杆菌属菌种中。为了确定pB8 - 51是否能被任何已知的拟杆菌属接合元件所转移，我们构建了一个含有pB8 - 51的大肠杆菌 - 拟杆菌穿梭载体pVAL - 1。我们构建了携带pVAL - 1和各种拟杆菌属接合元件的均匀拟杆菌0061衍生物。所测试的拟杆菌属接合元件有6种接合型四环素抗性（Tcr）元件（似乎是染色体元件），即Tcr ERL、Tcr V479、Tcr Emr ERL、Tcr Emr 12256、Tcr Emr DOT和Tcr Emr CEST，以及接合型红霉素抗性（Emr）质粒pBF4。除了Tcr ERL外，这些Tcr接合元件尚未得到广泛的表征。所测试的所有6种Tcr元件都能以高频率（10^(-3)至10^(-5)）将pVAL - 1从一种拟杆菌菌株转移到另一种拟杆菌菌株，或从拟杆菌菌株转移到大肠杆菌。供体（含有其中一种Tcr元件和pVAL - 1）在每毫升含1微克四环素的培养基中预培养，可使pVAL - 1的转移效率提高20至10000倍，这取决于供体中存在哪种Tcr元件。pBF4的一个Emr衍生物（pBF4 delta E2）能以10^(-4)的频率将pVAL - 1从一种拟杆菌菌株转移到另一种拟杆菌菌株，但从拟杆菌菌株转移到大肠杆菌的效率不高。因此，Tcr接合元件和pBF4识别pB8 - 51上的一个转移区域。
