Abstract

A total of 62 Pseudomonas isolates were selected from a contaminated site at Sohag district and tested for their resistance tto cadmium metal. Isolate no. 22 was found to be the most resistant one and has a plasmid with molecular wt27.491 Kbp. The minimal inhibition concentrations (MIC) for the resistant (R) and adopted sensitive (S) isolates were 1.0 and 0.119 mmol L^-1, respectively. The growth, protein content and maximum specific growth rate (k) decreased with increasing concentrations of heavy metal. The generation time (T) increased with the addition of divalent cations (Fe²⁺, Mg²⁺ and Ca²⁺) plus cadmium. Under cadmium stress, three proteins of high molecular weights (208, 78 and 33.5 KD) were lost while one protein with low molecular weight (2.5 KD) was induced. LPS profile was modified under stress of CdCl₂. Absence of bands in region I, which represents the O-specific antigen, and region II (core-oligosaccharide linked to lipid A) were recorded at high concentrations of CdCl₂.

Key words: Pseudomonas aeruginosa, cadmium stress, heavy metal resistance.