Date Published: February 28, 2019
Publisher: Springer Berlin Heidelberg
Author(s): Lusine Matevosyan, Inga Bazukyan, Armen Trchounian.
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.
The reduction of pathogens growth in food and feed production and storage is very important, and the creation of new effective strategies for this purpose becomes more and more prospective. It has been known that lactic acid bacteria (LAB) produce several antimicrobial substances, including organic acids, other organic compounds, carbon dioxide, diacetyl, hydrogen peroxide and bacteriocins (Nes et al. 2011). It is also significant to define the role of metals in production of antimicrobial components and differentiate the metals that are essential for cells and included in composition of important enzymes (proteases, DNA polymerases, dipeptidases, tripeptidases, etc.). Such metals are calcium (Ca2+) and magnesium (Mg2+).
Interactions between metals and microorganisms are diverse, but can be divided into 3 major categories: metals essential for metabolism; metals which are accumulated; metals which undergo biochemical transformation (including leaching). Three individual functions were presented: metal ions act as catalytic centers of enzymes; metal ions, not primarily involved in the catalysis, act as binding groups to bring enzyme and substrate together; metal ions maintain physiological control (antagonism with other metals). More recently, other aspects of the role of metal ions in metabolism have been investigated, e.g. the involvement of metal ions in the reactivation of EDTA inhibited proteolytic enzymes from LAB and the narrow tolerance for specific metals in the synthesis of secondary metabolites (Weinberg 1970, 1978). The ionic environment may interfere with bacterial cell walls, especially in Gram-positive bacteria such as Lactobacillus and Streptococcus which contain teichoic and teichuronic acids (Ellwood and Tempest 1972). The relative affinities of various cations for Gram-positive bacterial cell walls have been reported by Marquis et al. (Marquis et al. 1976).