Spontaneous mutations and mutational responses to penicillin treatment in the bacterial pathogen Streptococcus...

Area of Science:

• Microbiology
• Genetics
• Evolutionary Biology

Background:

• Bacteria with functional DNA repair systems typically show low mutation rates due to selection for genomic stability.
• Streptococcus pneumoniae is a significant human pathogen responsible for various common diseases.

Purpose of the Study:

• To investigate the spontaneous mutation rate of the wild-type Streptococcus pneumoniae D39.
• To understand the underlying mechanisms and evolutionary implications of its mutation rate.

Main Methods:

• Mutation-accumulation (MA) experiments were conducted on Streptococcus pneumoniae D39.
• DNA mismatch repair (MMR) efficiency was assessed.
• The effect of penicillin treatment on mutation rate was examined.

Main Results:

• Streptococcus pneumoniae D39 displayed a high spontaneous mutation rate (0.02 per genome per cell division), significantly higher than other non-mutator bacteria.
• A pronounced mutation bias towards A/T was observed.
• The pathogen exhibited the lowest DNA mismatch-repair efficiency among bacteria.
• Penicillin treatment did not increase the mutation rate, as it does not induce DNA damage in this species.

Conclusions:

• The high mutation rate in S. pneumoniae may be attributed to reduced selection efficiency linked to a small effective population size.
• These findings are relevant to understanding pathogen evolution within host environments.
• The study provides crucial insights into the genomic stability and evolutionary potential of Streptococcus pneumoniae.