Characterization of Streptococcus sanguis Mutants Generated by Signature-Tagged Mutagenesis

摘要

Streptococcus sanguis belongs to the viridans group of oral streptococci, which cause 40-50% of human native valve endocarditis. Identification of new virulence factors is important for drug and vaccine development. A transposon-based random mutagenesis technique called signature-tagged mutagenesis (STM) was used to search for new virulence factors. Four signature-tagged mutants exhibiting decreased virulence in a rabbit model were chosen for characterization. Growth studies suggested that poor growth may have contributed to their decreased virulence. Next, mutant DNA was cloned into Escherichia coli to characterize the sequences flanking the transposon. Lastly, all mutants were characterized using arbitrarily primed polymerase chain reaction. It was determined that plasmid DNA was inserted with the transposon in three of the four mutants. Additionally, in two of the mutants, the transposon was flanked by apparently non-conflguous sequences. These surprising results may be due to unforeseen events occurring during the in vitro transposition stage of STM.