Inhibition of Aspergillus flavus and Selected Gram-positive Bacteria by Chelation of Essential Metal Cations by
S J Knabel1,2, H W Walker1, P A Hartman2
1Departments of Food Technology, Iowa State University, Ames, Iowa 50011.
Abstract:
A simple well-plate technique was utilized to determine the effect of various metals on the growth of microorganisms in media containing different polyphosphates. Aspergillus flavus and four gram-positive bacteria were completely inhibited by media containing 1% of various alkaline polyphosphates, whereas four gram-negative bacteria were not. Significant differences were observed between the type of polyphosphate added, the type of metal added, and the species of gram-positive bacterium inhibited. The addition of Mg2+ stimulated growth of A. flavus and Bacillus cereus in the presence of tetrasodium pyrophosphate, whereas Mn2+ permitted growth of A. flavus and Staphylococcus aureus in the presence of sodium hexametaphosphate. Iron supplementation allowed the growth of S. aureus and Listeria monocytogenes on media containing 1 % tetrasodium pyrophosphate. A method for determining the amount of calcium and magnesium in water was modified to detect free Mg2+ by replacing EDTA with phosphate. The addition of free Mg2+, but not Mg2+ chelated by tetrasodium pyrophosphate, permitted the growth of B. cereus on a medium containing tetrasodium pyrophosphate. It is speculated that polyphosphates specifically inhibited A. flavus and gram-positive bacteria by removing essential metals from cation-binding sites located within their cell walls.
Related Concept Videos
Bonding in Metals
Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
Metallic Solids
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability....
Alkali Metals
Table 1: Properties of the alkali metals
Feedback Inhibition
Compounds Essential to Human Function
Inorganic Compounds Essential to Human Functioning
Inorganic compounds essential to human functioning include water, salts, acids, and bases. These compounds are inorganic, i.e., they do not have a carbon-hydrogen bond. Water...


