Short-sequence tandem and nontandem DNA repeats and endogenous hydrogen peroxide production contribute to genetic instability of Streptococcus pneumoniae.
نویسندگان
چکیده
Loss-of-function mutations in the following seven pneumococcal genes were detected and analyzed: pspA, spxB, xba, licD2, lytA, nanA, and atpC. Factors associated with these mutations included (i) frameshifts caused by reversible gain and loss of single bases within homopolymeric repeats as short as 6 bases, (ii) deletions caused by recombinational events between nontandem direct repeats as short as 8 bases, and (iii) substitutions of guanine residues caused at an increased frequency by the high levels of hydrogen peroxide (>2 mM) typically generated by this species under aerobic growth conditions. The latter accounted for a frequency as high as 2.8 x 10(-6) for spontaneous mutation to resistance to optochin and was 10- to 200-fold lower in the absence of detectable levels of H2O2. Some of these mutations appear to have been selected for in vivo during pneumococcal infection, perhaps as a consequence of immune pressure or oxidative stress.
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عنوان ژورنال:
- Journal of bacteriology
دوره 184 16 شماره
صفحات -
تاریخ انتشار 2002