Germicidal Action of Some Metals/Metal Ions in Combating <i>E. coli</i> Bacteria in Relation to Their Electro-Chemical Properties

Abstract

The germicidal properties of some metals and metal compounds were investigated in relation to their electro-chemical properties that may play a role in the inactivation of E. coli bacteria. These properties included the atomic and ionic radii, ionization energy, oxidation state, energy of formation with hydro-sulfide groups, and the redox potential of the metals. Cultures of E. coli bacteria with predetermined numbers of colony-forming units (CFU's) were brought in contact with the metals as well as metal compounds, using Eosin methylene blue agar medium and sterilized, distilled water. The rate of inactivation was determined by counting the CFU's at predefined intervals of time after inoculation. The experimental results showed that the rate of inactivation increases with increasing ionization energy of the metals. While the rate of inactivation increases with decreasing atomic radii for some of the transition metals, there is no apparent relationship between ionic radius and rate of inactivation for the metal compounds. In addition, non-transition group III metals such as aluminum and indium showed higher rates of inactivation that are comparable to the action of silver. This is probably due to the increase in coagulation potential and the resulting adsorption of bacteria, because a larger number of ions are able electrons carried by these atoms. In general, there is a difference between the atoms and the ions in terms of their rate of inactivation. This difference increases amongst the transition metals that have lower oxidation potential, lower ionization potential as well as larger ionic radius. The results also showed that for the metals, adsorption through coagulation is an important fact or that is responsible for inactivation of E. coli. For the metal compounds, additional mechanisms such as direct reaction through complex formation, physico-chemical distortion of the cell structure through direct entry of the ions into the cell, may contribute towards greater inactivation.

The Pathogenicity ofShewanella algaeand Ability to Tolerate a Wide Range of Temperatures and Salinities

“…Recent studies showing that non-indole-producing bacteria generate various oxygenases which may degrade indole or interfere with indole signaling [ 56 , 57 ]. Many oxygenase and reductase reactions may be involved in metal ion facilitation in bacteria [ 58 ]. The ability of S. oneidensis to reduce oxidized metals or nitrate effectively has been identified as an important intrinsic activity of Shewanella species [ 59 – 62 ].…”

In-vitro inactivation of Escherichia coli of surface water using metals

“…In disinfection systems that contain both copper and silver, copper ions permeate the cell wall, opening a pathway for silver ions to permeate into the microorganisms. The binding of the silver ions to the cell's proteins, respiratory enzymes, DNA, and RNA causes the cell's entire life support system to become immobilized (Lenntech, 2010).According to a recent study on copper surfaces showed that hydroxyl radicals in the solution are responsible for microbes fatal action (Oyanedel et al, 2008;Santo et al, 2011. This method is typically employed in large-scale, commercial water disinfection systems where metal ions are produced chemically or electrolytically, and it has been found to be extremely successful (Varkey, 2010). The fact that electrolytic systems require a power source in order to function is a drawback (Mehtar et al, 2008).…”

Influence of Metal Oxide Nanoparticles as Antimicrobial Additives Embedded in Waterborne Coating Binders Based on Self-Crosslinking Acrylic Latex

“…In contrast, the biocidal efficiency of latex films with MgO nanoparticles can be explained by the high alkalinity of the coating film (see pH data in Table 2), which creates an unfavourable environment for MOs and, in addition, increases the activity of reactive oxygen species [83]. It should be emphasized here that the exact antimicrobial mechanism of MeO nanoparticles has not yet been clearly elucidated, but lipid peroxidation, the formation of reactive oxygen species, the presence of metal cations destroying MO enzymes, or the internalization of nanoparticles have been assumed [117][118][119][120]. It is further hypothesized that when metal cations enter a bacterial cell, the DNA molecule changes to a condensed form and loses its ability to replicate, leading to cell death [121,122].…”