Metal-ion assisted detergent action on bacterial growth: detergent specificity and mechanism of inhibition

Detergents in general inhibit bacterial growth. The anionic detergent, sodium lauryl sulphate (NaLS), seems to have a more specific inhibitory effect on growth of the Gram-positive Bacillus subtilis than on growth of the Gram-negative Escherichia coli. The specificity of anionic detergent towards B. subtilis has been traced to the difference in the nature of the cell wall. The inhibitory action of the detergent is markedly increased by the presence of metal ions like Cd++ or Mg++, due probably to the increase in the micellar phase, facilitating the solubilisation of bacterial species in the inner core of micelles. While metal ions like Cu++ do not influence the activity of NaLS, Na+, Ca++ or Mn++ ions seem to act against the detergent action on bacterial growth, probably by altering the structure of micelles.