摘要
Concentrations of Na+, K+ and Ca2+ in the growth medium were varied within limits normally found in vivo to determine how cation concentrations affect the sensitivity of ruminal bacteria to the ionophores, monensin (a Na+/H+ and K+/H+ exchanger) and tetronasin (Ca2+/H+). High [Na+] (172 mM cf. 137 mM in control medium) enhanced the efficacy of monensin towards Eubacterium ruminantium 2388, Streptococcus bovis C277, Lactobacillus casei LB17 and Prevotella albensis M384. High [K+] (35 mM cf. 19 mM) alone caused a decreased potency of both ionophores, except with L. casei. Added Ca2+ (7.4 cf. 2.8 mM) increased the potency of tetronasin when [Na+] was low. High [Na+] alone also potentiated the efficacy of tetronasin. Monensin caused intracellular [Na+] and [K+] to be decreased in the most sensitive of these organisms, E. ruminantium, whereas only intracellular [Ca2+] fell with tetronasin. The changes were small; however, Δp fell by only 20 mV after 2 h when ionophores caused immediate cessation of growth. ATP concentrations fell by 77% and 75% with monensin and tetronasin, respectively. Thus, altering cation concentrations might be used to potentiate the efficacy of ionophores, by increasing the rate of energy expenditure to maintain ionic homoeostasis in sensitive bacteria.
摘要译文
娜SUP / SUP的浓度，向上 / SUP和Ca SUP 2 / SUP在生长培养基中在体内通常发现，以确定阳离子浓度如何影响瘤胃细菌的敏感性，离子载体限度内变化，莫能菌素（一捺SUP / SUP / H SUP / SUP和K SUP / SUP / H SUP / SUP器）和tetronasin（CA SUP 2 / SUP / H SUP / SUP）。高[娜SUP / SUP]（172毫米参137毫米控制介质）增强莫能菌素的药效对真杆菌反刍2388，牛链球菌C277，干酪乳杆菌LB17和普雷沃albensis M384。高[K SUP / SUP]（35毫米参见19毫米）一手造成这两种离子载体的效力下降，但与干酪乳杆菌。补充钙SUP 2 / SUP（7.4参见2。8毫米）增加tetronasin的效力时，[娜SUP / SUP]低。高〔娜SUP / SUP]单独也增效tetronasin的功效。莫能菌素引起细胞内的[娜SUP / SUP]和[K SUP / SUP]，在最敏感的这些生物，E.反刍的减少，而只有细胞内的[Ca SUP 2 / SUP]爱上了tetronasin。这些变化很小;然而，ATP浓度下降了77％和75％，与莫能菌素和tetronasin分别。因此，改变阳离子浓度可能被用来加强离子载体的功效，通过增加能量消耗率保持敏感细菌的离子环境稳定。
C. James Newbold[†]; Robert John Wallace[*]; Nicola D. Walker-Bax[‡. Potentiation by metal ions of the efficacy of the ionophores, monensin and tetronasin, towards four species of ruminal bacteria[J]. FEMS Microbiology Letters, 2013,338(2): 161-167