ISSN:
1432-0991
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The wild-type strain and mutants ofEscherichia coli lacking Mn-superoxide dismutase (Sod A) or Fe-superoxide dismutase (Sod B) are compared for their sensitivity to the H2O2 insult (exposure for 15 min at 37°C, in M9 salts). Whereas mode one killing is similar in superoxide dismutase mutants and wild-type cells, the latter strain appears to be more resistant than the former ones to mode two lethality. Furthermore, Sod B cells, as well as wild-type cells but unlike Sod A cells, are capable of reversing the toxicity of the oxidant (even in the presence of chloramphenicol), this effect being observed by gradually increasing the H2O2 concentration from 2.5 to 10 mM. It is concluded that (a) superoxide ions may not be involved in the production of mode one killing by H2O2, although further experiments are needed to validate or modify this hypothesis; (b) superoxide ions mediate mode two killing by H2O2, possibly by reducing trivalent iron to the divalent form; and (c) the intervening zone of partial resistance observed in wild-type and Sod B cells exposed to intermediate H2O2 concentrations is not a consequence of Mn-superoxide dismutase induction; it would appear, however, that cells lacking this superoxide dismutase isoenzyme are not proficient in this acquired response.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01568796
