title: The pdh operon is expressed in a subpopulation of stationary-phase bacteria and is important for survival of sugar-starved Streptococcus mutans.
abstract: Streptococcus mutans is a facultative member of the oral plaque and is associated with dental caries. It is able to survive long periods of sugar starvation. We show here that inactivation of pdhD, putatively encoding a subunit of the pyruvate dehydrogenase complex, impairs survival of both batch cultures and biofilms. We show that pdhD and the downstream genes pdhA, pdhB, and pdhC form an operon that is predominantly transcribed in stationary phase. Analysis with fluorescent reporters revealed a bimodal expression pattern for the pdh promoter, with less than 1% of stationary-phase populations expressing pdh. When it was first detected, after 1 day of sugar starvation in batch culture, expression was mostly in individual bacteria. At later times, expressing bacteria were often in chains. The lengths of the chains increased with time. We infer that the pdh-expressing subpopulation is able grow and divide and to persist for extended times in stationary phase.
authors.affiliation: Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors.forename: Monica
authors.initials: M
authors.lastname: Busuioc
authors.forename: Bettina A
authors.initials: BA
authors.lastname: Buttaro
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Piggot
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D050260:Carbohydrate Metabolism; D003470:Culture Media; D003773:Dental Plaque / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D009876:Operon / Q000235:genetics / Q000502:physiology*; D011768:Pyruvate Dehydrogenase Complex / Q000235:genetics / Q000378:metabolism*; D013295:Streptococcus mutans / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D011768:Pyruvate Dehydrogenase Complex; D005947:Glucose