Point mutations in functionally diverse genes are associated with increased natural DNA transformation in multidrug resistant Streptococcus pneumoniae.

Abstract

DNA transformation is key for phenotypic diversity and adaptation of Streptococcus pneumoniae including in the emergence of multidrug resistance (MDR). Under laboratory conditions, DNA transformation is facilitated by the artificial triggering of competence by the competence stimulating peptide (CSP). In ongoing DNA transformation work, we observed that exogenous CSP was dispensable depending on the combination of strains and culture media. Here, we carried out a chemogenomic screen to select for S. pneumoniae mutants capable of natural transformation in medium that normally would not sustain natural transformation. Our chemogenomic screen relied on chemical mutagenesis followed by selection of mutants with increased DNA transformation capacities. Sequencing the genome of these mutants revealed an abundance and diversity of mutated genes proven experimentally to increase natural transformation. A genome wide association study between MDR and sensitive clinical isolates revealed gene mutations associated with MDR, many of which intersected with those pinpointed by our chemogenomic screens and that were proven to increase natural transformation. S. pneumoniae has adopted DNA transformation as its lifestyle and can select for mutations facilitating DNA transformation.