Open AccessPotentiation by metal ions of the efficacy of the ionophores, monensin and tetronasin, towards four species of ruminal bacteria
Author(s) -
Newbold C. James,
Wallace Robert John,
WalkerBax Nicola D.
Publication year - 2013
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/1574-6968.12044
Subject(s) - monensin , long term potentiation , bacteria , chemistry , metal ions in aqueous solution , metal , microbiology and biotechnology , biochemistry , biology , organic chemistry , genetics , receptor
Abstract Concentrations of Na + , K + and Ca 2+ 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 ( Ca 2+ / H + ). High [ Na + ] (172 mM cf. 137 mM in control medium) enhanced the efficacy of monensin towards E ubacterium ruminantium 2388, S treptococcus bovis C 277, L actobacillus casei LB 17 and P revotella albensis M 384. High [ K + ] (35 mM cf. 19 mM) alone caused a decreased potency of both ionophores, except with L . casei . Added Ca 2+ (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 [Ca 2+ ] fell with tetronasin. The changes were small; however, Δ p 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.