Abstract
Iron-free lactoferrin or iron-free transferrin inhibited the growth but did not affect the viability of Yersinia pseudotuberculosis cells that were present in iron-complete BHI broth or in BHI broth iron-depleted by MgCO3. This type of inhibition was reversed by the addition of iron-saturated lactoferrin or iron-saturated transferrin, which appeared to be capable of serving as a source of iron in the above iron-depleted medium, or by transfer to iron-complete BHI broth. In contrast, there was a rapid loss of viability for those cells which were suspended in deionized water and were treated by iron-free lactoferrin or iron-free transferrin. The iron-irreversible inhibition which was observed in the absence of medium suggests that both lactoferrin and transferrin have a direct bactericidal effect on Y. pseudotuberculosis that cannot be attributed to simple iron-deprivation.