Two classes of tributyltin (TBT) resistant, spontaneous mutants of Escherichia coli K-12 were isolated, using a cytochrome containing (W 1485) and a cytochrome deficient (SASX76) strain. In contrast to the cytochrome sufficient strain, the cytochrome deficient strain was found to be fifty times more sensitive to TBT. The class I mutants, isolated from strain W 1485, also showed crossresistance to triphenyltin (TPT). As compared to its wild type parent, the TBT-resistant mutants exhibited mucoid colony type, aberrant cell morphology and reduced uptake of TPT. Based on these results, it was suggested that the resistance of class I mutants to TBT may be associated with above mentioned alterations. The class II TBT-resistant mutants were isolated from the cytochrome deficient strain, SASX76. In comparison to class I mutants, these class II mutants were found to have TBT-resistant membrane bound adenosine triphosphatase (ATPase) which may account for their resistance to TBT
Isolation and characterization of norfloxacin-resistant mutants of Escherichia coli K-12.
