Resistance to Mercuric Chloride in Pseudomonas K-62

Mercuric ion-resistant mechanism in Pseudomonas K-62 was investigated by isolating a mercuric ion-sensitive mutant strain (H-2 strain) from a resistant wild-type strain (P strain) and comparing the physiological properties of these two strains. Growth curves obtained in mercuric ion-containing medium suggested that P strain constitutively has a resistant mechanism. The capacity of P and H-2 strains to decrease the concentration of mercuric ions in the medium was found to be almost equal; thus, the presence of a resistant mechanism was expected other than MMR-enzyme, which is an inducible system. From the characteristic property of the inhibitory effect of mercuric ions on respiration of the two strains, a resistant mechanism, a permeability barrier mechanism, was proposed. The barrier mechanism in P strain traps mercuric ions with high selectivity to prevent the penetration of ions to the intracellular space where the functional units are located. Finally, the resistance mechanism to mercuric ions in the bacterium was discussed including the MMR-enzyme system and the barrier mechanism.