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Updated: Apr 30, 2026
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Heterogeneity in the frequency and characteristics of homologous recombination in pneumococcal evolution
Rafal Mostowy1, Nicholas J Croucher2, William P Hanage3
1Department of Infectious Disease Epidemiology, Imperial College London, St Mary's Campus, London, United Kingdom.
Abstract:
The bacterium Streptococcus pneumoniae (pneumococcus) is one of the most important human bacterial pathogens, and a leading cause of morbidity and mortality worldwide. The pneumococcus is also known for undergoing extensive homologous recombination via transformation with exogenous DNA. It has been shown that recombination has a major impact on the evolution of the pathogen, including acquisition of antibiotic resistance and serotype-switching. Nevertheless, the mechanism and the rates of recombination in an epidemiological context remain poorly understood. Here, we proposed several mathematical models to describe the rate and size of recombination in the evolutionary history of two very distinct pneumococcal lineages, PMEN1 and CC180. We found that, in both lineages, the process of homologous recombination was best described by a heterogeneous model of recombination with single, short, frequent replacements, which we call micro-recombinations, and rarer, multi-fragment, saltational replacements, which we call macro-recombinations. Macro-recombination was associated with major phenotypic changes, including serotype-switching events, and thus was a major driver of the diversification of the pathogen. We critically evaluate biological and epidemiological processes that could give rise to the micro-recombination and macro-recombination processes.
Insights
Streptococcus pneumoniae undergoes micro- and macro-recombinations, driving its evolution. Macro-recombinations, though rare, significantly impact pathogen diversification and serotype-switching.
Area of Science:
- Microbiology
- Evolutionary Biology
- Epidemiology
Background:
- Streptococcus pneumoniae is a major human pathogen causing significant morbidity and mortality.
- Pneumococcus extensively uses homologous recombination for genetic exchange, impacting antibiotic resistance and serotype evolution.
- The precise mechanisms and epidemiological rates of pneumococcal recombination remain unclear.
Purpose of the Study:
- To develop mathematical models for pneumococcal recombination rates and sizes.
- To analyze recombination in two distinct pneumococcal lineages (PMEN1 and CC180).
- To elucidate the role of different recombination types in pathogen evolution.
Main Methods:
- Mathematical modeling of recombination processes.
- Analysis of homologous recombination in Streptococcus pneumoniae.
- Comparative study of two distinct pneumococcal lineages.
Main Results:
- Homologous recombination in both lineages is best described by a heterogeneous model.
- Identified frequent, short "micro-recombinations" and rarer, larger "macro-recombinations".
- Macro-recombinations correlate with significant phenotypic changes, including serotype-switching, driving pathogen diversification.
Conclusions:
- Pneumococcal evolution is shaped by both micro- and macro-recombination events.
- Macro-recombination is a key driver of Streptococcus pneumoniae diversification and adaptation.
- Further research is needed to understand the biological and epidemiological underpinnings of these recombination processes.
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