Pakistan Research Repository


Raihan, Salma (2001) STUDIES ON MECHANISM OF BACTERIAL RESISTANCE TO CADMIUM AND NICKEL. PhD thesis, University of Karachi, Karachi.



Consideration of controlling environmental pollution has concentrated on the possibility of using multiple resistant bacteria for removal of heavy metals from polluted effluent or sediments through a form of bioaccumulation that would follow the different mechanisms of resistance. For this purpose thirteen metallotolerant bacteria designated as CMG51 to CMG64 were isolated from effluent of local industries that include P. aeruginosa, E. coli, Moraxello, Bacillus and Enterococcuis species. Selection of isolates were based on their high resistance to cadmium and nickel. All the isolates showed effect of pH, temperature, and growth media on metal resistance. Similarly metal concentration also showed a direct effected on colonial and cellular morphology as well as a growth retarding effect of metal salts was also observed. Studies on the mechanism of metal resistance showed that different mechanisms operate in different isolates. On the basis of these studies one of the isolates CMG52 showed the involvement of permeability barrier ie 11 metal resistance. and of thirteen, four isolates CMG58, CMG59, CMG61, and CMG64 harbored low molecular weight plasmids that was confirmed by curing, conjugation, and transformation to involve in metal resistance. Plasmid hearing isolates showed higher protein content when grown in presence of metal salts. Likewise, qualitative analysis showed presence of additional protein band in presence or plasmid whereas no additional band was observed in cured derivatives when grown in subinhibitory concentration of metal salts. Variations in molecular weights of protein suggested the possibility that these metallotolerant proteins might be adopted version of some pre-existing proteins. To have the practical application of the following study, lab. scale bioreactors were constructed by developing the biofilms of MGG4 on locally available support materials and successfully used for cadmium removal.

Item Type:Thesis (PhD)
Uncontrolled Keywords:bacterial resistance, cadmium, nickel, environmental pollution, multiple resistant bacteria, heavy metals, p. aeruginosa, e. coli, moraxello, bacillus, enterococcuis, industrial wastes, chemical wastes, bioreactors
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Evolution & genetics (c1.6)
ID Code:1370
Deposited By:Mr. Muhammad Asif
Deposited On:14 Feb 2007
Last Modified:04 Oct 2007 21:06

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