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Properties of ionophore‐resistant Bacteroides rurninicola enriched by cultivation in the presence of tetronasin
Author(s) -
Newbold C.J.,
Wallace R.J.,
Watt Nicola D.
Publication year - 1992
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1992.tb04883.x
Subject(s) - ionophore , chemistry , biology , biochemistry , membrane
Bacteroides ruminicola M384 was grown in the presence of increasing concentrations of tetronasin, an ionophore that has been developed as a feed additive for ruminants. The resulting culture, B. ruminicola M384/Tn R , was then maintained in medium containing 0.1 pg tetronasin/ml. Growth of the parent strain was eliminated by the addition of 0.1 ug tetronasin/ml, but the growth rate of B. ruminicola M384/Tn R , which grew more slowly than the parent strain, was unaffected by adding tetronasin. Bacteroides ruminicola M384/Tn R retained its resistance to tetronasin even after repeated subculture in the absence of the ionophore, suggesting that a mutation had occurred. The absence of plasmids in individual colonies of B. ruminicola M384/Tn R implied that the mutation was chromosomal. Bacteroides ruminicola M384/Tn R was also more resistant to the ionophores monensin and lasalocid and, to a lesser degree, to the antibiotic avoparcin than B. ruminicola M384. Binding of [ 14 C]tetronasin to B. ruminicola M384/Tn R was lower than binding of the ionophore to the parent stain, and this difference was eliminated by washing cells with EDTA. The peptidolytic activity of B. ruminicola M384 towards triphenylalanine ( M r = 460) was unaffected in B. ruminicola M384/Tn R , but the rate of breakdown of tetra‐phenylalanine ( M r = 607) was decreased. This difference was also abolished by EDTA. It was concluded that growth of B. ruminicola in the presence of tetronasin resulted in a mutation affecting the permeability of the cell envelope, such that permeation of tetronasin and molecules of a similar size ( M r = 628) was decreased.