Wampler J L, Martin S A, Hill G M
Department of Animal and Dairy Science, University of Georgia, Athens 30602-2771, USA.
J Anim Sci. 1998 Oct;76(10):2730-6. doi: 10.2527/1998.76102730x.
The objective of this study was to compare the effects of laidlomycin propionate and monensin on cell growth, glucose fermentation, and glucose uptake in Streptococcus bovis strain JB1 and Selenomonas ruminantium strain HD4. Experiments were also conducted to compare the effects of both ionophores on sodium-dependent serine transport and cell yield in S. bovis. Batch cultures (500 mL) of each bacterium were grown on 3.6 g/L D-glucose in semidefined medium and treated with either 5 ppm monensin or 2 ppm laidlomycin propionate (n=2). Cell growth was monitored by measuring optical density at 600 nm (OD600). Glucose and L-lactate concentrations were measured using coupled enzyme assays. In S. bovis, both monensin and laidlomycin propionate decreased OD600, glucose utilization, and L-lactate production. Neither ionophore had any effect on glucose utilization by S. ruminantium. [14C]Glucose uptake between 5 and 30 min by both bacteria was not altered by either ionophore. Sodium-dependent [14C]serine uptake by S. bovis was inhibited by monensin but not laidlomycin propionate. When S. bovis was grown in glucose-limited continuous culture (dilution rate=.10 h(-1)) at extracellular pH 6.7, increasing concentrations of both ionophores decreased bacterial yield, and both ionophores were more potent at an extracellular pH of 5.7. However, monensin was a more potent inhibitor than laidlomycin propionate at pH 6.7 and 5.7. Collectively, these results suggest that the ionophore laidlomycin propionate inhibits the Gram-positive bacterium S. bovis in a manner similar to that of monensin, but, at the concentrations used in this study, laidlomycin propionate seems to be less potent than monensin in inhibiting serine uptake and cell yield.
本研究的目的是比较丙酸拉地霉素和莫能菌素对牛链球菌JB1菌株及反刍月形单胞菌HD4菌株的细胞生长、葡萄糖发酵和葡萄糖摄取的影响。还进行了实验以比较这两种离子载体对牛链球菌中钠依赖性丝氨酸转运和细胞产量的影响。每种细菌的分批培养物（500 mL）在半限定培养基中的3.6 g/L D-葡萄糖上生长，并用5 ppm莫能菌素或2 ppm丙酸拉地霉素处理（n = 2）。通过测量600 nm处的光密度（OD600）监测细胞生长。使用偶联酶测定法测量葡萄糖和L-乳酸浓度。在牛链球菌中，莫能菌素和丙酸拉地霉素均降低了OD600、葡萄糖利用率和L-乳酸产量。两种离子载体对反刍月形单胞菌的葡萄糖利用均无任何影响。两种离子载体均未改变两种细菌在5至30分钟之间对[14C]葡萄糖的摄取。莫能菌素抑制牛链球菌对钠依赖性[14C]丝氨酸的摄取，但丙酸拉地霉素无此作用。当牛链球菌在细胞外pH 6.7的葡萄糖限制连续培养（稀释率 = 0.10 h(-1)）中生长时，两种离子载体浓度的增加均降低了细菌产量，并且在细胞外pH 5.7时两种离子载体的作用更强。然而，在pH 6.7和5.7时，莫能菌素比丙酸拉地霉素是更有效的抑制剂。总体而言，这些结果表明，离子载体丙酸拉地霉素以类似于莫能菌素的方式抑制革兰氏阳性菌牛链球菌，但在本研究中使用的浓度下，丙酸拉地霉素在抑制丝氨酸摄取和细胞产量方面似乎比莫能菌素效力更低。
