Cadmium-induced alterations in the protein profiles of two cyanobacterial isolates, CdO-10 and Bol-32 (Chroococcus spp.)
1999
Santos, C.A.Q. | Rivero, G.C. (Philippines Univ. Diliman, Diliman, Quezon City (Philippines). Inst. of Biology)
Two cyanobacterial isolates. viz. CdO-10 and Bol-32 (Chroococcus spp.), were subjected to various levels of CdCl2 (0.05 ppm, 0.5 ppm and 5.0 ppm). The physiological effects of cadmium were evaluated with respect to growth, total protein content and protein profile. Growth responses were determined by spectrophotometric analysis of chlorophyll a levels, total protein content by Coomassie Brilliant Blue protein assay and protein profile by one-dimensional sodium dodecyl sulfate (1-D SDS) and native (non-denaturing) polyacrylamide gel electrophoresis (PAGE). Growth at 0.05 ppm and 0.5 ppm CdCl2 of both the CdO-10 and Bol-32 isolates were significantly reduced but not completely inhibited. Between the two cyanobacterial isolates, CdO-10 was more tolerant to cadmium stress. Growth at 5.0 ppm CdCl2 of both the CdO-10 and Bol-32 isolates were completely inhibited. Total protein content reflected the results of the growth curve, i.e., decreasing protein content of cultures grown in media with CdCl2. Protein profiles of cultures exposed to 0.05 ppm and 0.5 ppm CdCl2, showed several alterations, including the presence of new protein bands. These new proteins may be stress proteins that enable the cyanobacteria to cope with cadmium stress. New protein bands were observed in the soluble and crude membrane protein profiles of CdO-10 cultures subjected to 0.05 ppm and 0.5 ppm CdCl2. In Bol-32 culture, however, new protein bands were not observed in the soluble protein profiles at their logarithmic phase of growth. The absence of cytosolic stress proteins during this phase of growth may explain the lesser tolerance of the Bol-32 isolate to cadmium stress
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