Callaway T R, Russell J B
Department of Microbiology, Cornell University, Ithaca, New York 14853, USA.
Appl Environ Microbiol. 1999 Nov;65(11):4753-9. doi: 10.1128/AEM.65.11.4753-4759.1999.
Prevotella bryantii cultures treated with monensin grew more slowly than untreated cultures, but only if the monensin concentration was greater than 1 microM. Cultures that were repeatedly transferred (eight transfers or 25 doublings) with monensin always grew rapidly, even at a 10 microM concentration. The amount of monensin needed to facilitate half-maximal potassium depletion (K(d)) from monensin-selected cells was 16-fold greater than "unadapted" wild-type cultures (3,200 versus 200 nM). Cells taken from continuous culture had a K(d) of 100 nM, and these inocula could not grow in batch culture when the monensin concentration was greater than 300 nM. Continuous cultures treated with monensin nearly washed out, but the surviving cells had a K(d) of 1,300 nM. When wild-type cells were transferred in batch culture with 10 microM monensin, the K(d) did not reach its maximum value (3,200 nM) until after eight transfers (25 doublings). K(d) declined when monensin was removed, and it took eight transfers to reach the control value (200 nM). The most probable number of wild-type cells was 1,000-fold lower than of the monensin-selected cells, but calculations based on relative growth advantage and K(d) indicated that the wild-type culture had 1 to 10% highly monensin-resistant cells. Cell pellets of wild-type cultures were more difficult to disperse than were monensin-selected cells, and water-soluble phenol extracts of monensin-selected cells had 1.8-fold more anthrone-reactive material than did the wild type. Wild-type cultures that were washed in Tris buffer (pH 8.0) released little alkaline phosphatase and were agglutinated by lysozyme. Monensin-selected cultures leaked ninefold more alkaline phosphatase and were not agglutinated by lysozyme. Wild-type colonies taken from high-dilution agar roll tubes retained the lysozyme agglutination phenotype even if transferred with monensin, and monensin-selected colonies were never agglutinated. These observations indicated that wild-type P. bryantii cultures had a subpopulation with different outer membrane characteristics and increased monensin resistance.
用莫能菌素处理的布氏普雷沃氏菌培养物生长速度比未处理的培养物慢，但前提是莫能菌素浓度大于1微摩尔。用莫能菌素反复传代（八次传代或25次倍增）的培养物总是生长迅速，即使在10微摩尔浓度下也是如此。促进莫能菌素选择的细胞中半数最大钾耗竭（K(d)）所需的莫能菌素量比“未适应的”野生型培养物大16倍（3200对200纳摩尔）。取自连续培养物的细胞K(d)为100纳摩尔，当莫能菌素浓度大于300纳摩尔时，这些接种物在分批培养中无法生长。用莫能菌素处理的连续培养物几乎全部消失，但存活细胞的K(d)为1300纳摩尔。当野生型细胞在含有10微摩尔莫能菌素的分批培养中转代时，K(d)直到八次传代（25次倍增）后才达到其最大值（3200纳摩尔）。去除莫能菌素后K(d)下降，需要八次传代才能达到对照值（200纳摩尔）。野生型细胞的最可能数量比莫能菌素选择的细胞低1000倍，但基于相对生长优势和K(d)的计算表明，野生型培养物有1%至10%的高度耐莫能菌素细胞。野生型培养物的细胞沉淀比莫能菌素选择的细胞更难分散，莫能菌素选择的细胞的水溶性酚提取物中蒽酮反应性物质比野生型多1.8倍。在Tris缓冲液（pH 8.0）中洗涤的野生型培养物释放的碱性磷酸酶很少，并且被溶菌酶凝集。莫能菌素选择的培养物泄漏的碱性磷酸酶多九倍，并且不被溶菌酶凝集。从高稀释度琼脂滚动管中取出的野生型菌落即使在用莫能菌素传代后仍保留溶菌酶凝集表型，而莫能菌素选择的菌落从未被凝集。这些观察结果表明，野生型布氏普雷沃氏菌培养物有一个具有不同外膜特征和增加的莫能菌素抗性的亚群。
