The Effects of Manganese (II) But Not Nickel (II) Ions on Enterococcus hirae Cell Growth, Redox Potential Decrease, and Proton-Coupled Membrane Transport

Comparative analysis of the effect of Ca and Mg ions on antibacterial activity of lactic acid bacteria isolates and their associations depending on cultivation conditions

The effects of divalent cations of Ca and Mg on antibacterial activity of lactic acid bacteria (LAB) isolates, as well as their different associations were studied. Most LAB strains and associations revealed significant inhibitory effects in MRS against Gram-positive and Gram-negative test-organisms at different Ca²⁺ and Mg²⁺ concentrations (determined specifically for each LAB strain and each association). Some LAB strains and communities inhibited the growth of pathogenic test-organisms depending on both ions concentrations and cultivation conditions. Interestingly, the presence of Mg ions in medium significantly decreased the antimicrobial activity of LAB communities against pathogenic test-organisms; on the other hand, the combined mixture of ions essentially increased the inhibitory effect in case of time-spaced cultivation. In contrast, the inhibitory effects of many associations were significantly increased at the presence of Mg²⁺ and especially ions combination in case of simultaneous cultivation. The addition of ions combination didn’t affect antibacterial activity of LAB isolates. The results allow us to conclude that Ca and Mg ions had inducible effects on antibacterial activity in case of simultaneous cultivation. This probably can be prospective for creation of new antimicrobial preparations and their possible application.

Cu(II), Fe(III) and Mn(II) combinations as environmental stress factors have distinguishing effects on Enterococcus hirae

Pollution by various heavy metals as environmental stress factors might affect bacteria. It was established that iron (Fe(III)), manganese (Mn(II)) and copper (Cu(II)) ion combinations caused effects on Enterococcus hirae that differed from the sum of the effects when the metals were added separately. It was shown that the Cu2+-Fe3+ combination decreased the growth and ATPase activity of membrane vesicles of wild-type E. hirae ATCC9790 and atpD mutant (with defective FoF1-ATPase) MS116. Addition of Mn2+-Fe3+ combinations within the same concentration range had no effects on growth compared to control (without heavy metals). ATPase activity was increased in the presence of Mn2+-Fe3+, while together with 0.2 mmol/L N,N'-dicyclohexylcarbodiimide (DCCD), ATPase activity was decreased compared to control (when only 0.2 mmol/L DCCD was present). These results indicate that heavy metals ion combinations probably affect the FOF1-ATPase, leading to conformational changes. Moreover the action may be direct or be mediated by environment redox potential. The effects observed when Fe3+ was added separately disappeared in both cases, which might be a result of competing processes between Fe3+ and other heavy metals. These findings are novel and improve the understanding of heavy metals ions effects on bacteria, and could be applied for regulation of stress response patterns in the environment.