Sk. Kazy et al., Copper uptake and its compartmentalization in Pseudomonas aeruginosa strains: Chemical nature of cellular metal, WORLD J MIC, 15(5), 1999, pp. 599-605
Copper-sensitive (Cu-s) and copper-resistant (Cu-r) strains of Pseudomonas
aeruginosa were characterized in terms of Cu2+ sensitivity, uptake and its
compartmentalization in the possible cell sectors. Minimum inhibitory conce
ntrations (MICs) of Cu2+ for the Cu-r strain (3.2 mM and 0.12 mM in enriche
d- and in minimal-medium, respectively) were almost 5-fold higher over that
of its sensitive counterpart. While Cu-s strain accumulated Cu2+ to a maxi
mum of 1.8 mu mol mg(-1) protein, Cu-r strain increased it to 2.37 mu mol m
g(-1) protein. Both the strains also demonstrated energy- and pH-dependent
Cu2+ uptake through the broad-substrate range divalent cation (Zn2+, Mg2+,
Co2+) uptake system as well as through the system specific for Cu2+. Cell-f
ractionation study revealed that in Cu-r strain, periplasm and membrane are
the main Cu2+ binding sites, whereas, in case of Cu-s strain, it is the cy
toplasm. The overall observations indicate that the Cu-r strain restricted
Cu2+ sequestration exterior to the cytoplasm as the possible strategy for C
u-resistance. The chemical nature of Cu2+ deposition in the respective stra
ins was also ascertained by X-ray powder diffraction analysis.