چكيده لاتين :
In this study the mechanism of chromium (Cr) and copper
(Cu) resistance in Pseudomonas aeruginosa was
investigated. For this reason, 50 isolates of this microorganism
were separated from 345 burn patients hospitalized
in burn unit of Kerman hospital, Iran, during
May 2001 to April 2002. Susceptibility/resistance of the
isolates to KCrO4, CuSO4, 5 H2O, AgNO3 and HgCl2
was determined by the agar dilution method. Among
them, 6% were highly resistant to KCrO4 (MIC 50 mM),
56% were resistant to CuSO4, 5 H2O (MIC 10 mM),
while, all the isolates were sensitive to HgCl2 and
AgNO3 with MIC range 0.5 -1 mM, respectively. Metal
resistant isolates exhibited different rate of Cr and Cu
accumulation. Isolates 14, 39 and 50 accumulated
11,14 and 15 mM/g biomass chromate, similarly, isolate
24 accumulated 8 mM/g biomass copper. The
accumulation of Cr and Cu was mainly surface bound
(biosorption), since considerable quantity of these
heavy metals was lost from the cell biomass after treating
the cells with 50 mM EDTA. Furthermore, P. aeruginosa
isolates did not produce H2S. X-ray diffraction
analysis of the cell surface exposed to the above
heavy metal ions revealed that Cr and Cu were mainly
deposited on the cell surface in the form of chromium
and copper sulfide (CrS and CuS). These complexes
were in the form of electron dense nanoparticles ranging
in size from 10 to 40 nm in diameter. However, cells
treated with EDTA did not show such complexes.
