Genomewide Identification of Essential Genes and Fitness Determinants of Streptococcus mutans UA159

Abstract

Transposon mutagenesis coupled with next-generation DNA sequencing (Tn-seq) is a powerful tool for discovering regions of the genome that are required for the survival of bacteria in different environments. We adapted this technique to the dental caries pathogen <i>Streptococcus mutans</i> UA159 and identified 11% of the genome as essential, with many genes encoding products required for replication, translation, lipid metabolism, and cell wall biogenesis. Comparison of the essential genome of <i>S. mutans</i> UA159 with those of selected other streptococci for which such information is available revealed several metabolic pathways and genes that are required in <i>S. mutans</i>, but not in some <i>Streptococcus</i> spp. We further identified genes that are essential for sustained growth in rich or defined medium, as well as for persistence <i>in vivo</i> in a rodent model of oral infection. Collectively, our results provide a novel and comprehensive view of the genes required for essential processes of <i>S. mutans</i>, many of which could represent potential targets for therapeutics. <b>IMPORTANCE</b> Tooth decay (dental caries) is a common cause of pain, impaired quality of life, and tooth loss in children and adults. It begins because of a compositional change in the microorganisms that colonize the tooth surface driven by repeated and sustained carbohydrate intake. Although several bacterial species are associated with tooth decay, <i>Streptococcus mutans</i> is the most common cause. Therefore, it is important to identify biological processes that contribute to the survival of <i>S. mutans</i> in the human mouth, with the aim of disrupting the processes with antimicrobial agents. We successfully applied Tn-seq to <i>S. mutans</i>, discovering genes that are required for survival, growth, and persistence, both in laboratory environments and in a mouse model of tooth decay. This work highlights new avenues for the control of an important human pathogen.