The involvement of the pyruvate dehydrogenase E1α subunit, inStreptococcus mutansacid tolerance

Abstract

Streptococcus mutans, an etiological agent of dental caries, is a normal inhabitant of dental plaque. Two main virulence factors of S. mutans are acidogenicity and aciduricity - the ability to produce acid and survive at low pH, respectively. Metabolic processes, including the catabolism of pyruvate, are finely regulated following acid exposure in S. mutans. Proteome analysis of the S. mutans acid response has shown pyruvate dehydrogenase A (PdhA) is upregulated. PdhA is the E1alphasubunit of the four-enzyme pyruvate dehydrogenase complex, responsible for the heterofermentative catalysis of pyruvate into acetyl-CoA. Acetyl-CoA is subsequently catalyzed into ethanol and acetate yielding additional ATP. This investigation examined the relationships between PdhA, aciduricity, and metabolism in S. mutans. An S. mutans pdhA knockout (PDHAKO) revealed an acid sensitive phenotype, displayed by increased doubling times, and decreased competitiveness in a biofermentor. Quantitative real-time PCR showed pdhA expression increased dramatically during acidic growth and under acid adaptation. Additionally, pdhA expression responded to conditions favoring heterofermentative growth; decreased in the presence of excess glucose, and increased during stationary phase compared with mid-log phase growth. This study demonstrated that in S. mutans, pdhA expression responds to conditions conducive to heterofermentation and deletion of pdhA resulted in decreased aciduricity.

A Stress-Inducible Quorum-Sensing Peptide Mediates the Formation of Persister Cells with Noninherited Multidrug Tolerance

“…Sequence analysis of the cloned insert revealed that these fragments corresponded to portions of SMU.402 and SMU.1278 encoding a pyruvate formate-lyase (PFL) and a putative phosphoglycolate phosphatase, respectively. Although work previously done in S. mutans has shown that PFL was responsible for pyruvate heterofermentation under anaerobic conditions (25), it is still unclear how this may relate to persistence.…”

Salmonella methylglyoxal detoxification by STM3117-encoded lactoylglutathione lyase affects virulence in coordination with Salmonella pathogenicity island 2 and phagosomal acidification

“…increased glycolytic flux of triose phosphates, threonine/glycine catabolism and acetone breakdown . However, regardless of the pathway of methylglyoxal formation, the detoxification is exclusively dependent on cellular glyoxalases (Ferguson et al, 1995;Korithoski et al, 2007;Ozyamak et al, 2010). The presence of a lactoylglutathione lyase (a putative glyoxalase I) gene in S. enterica serovar Typhimurium, Enteritidis, Gallinarum and other non-typhoidal serovars, but absence in typhoidal serovars might be indicative of host-specific acquisition of virulence determinants and metabolic requirements (Charles et al, 2009;Pujol et al, 2005;Rathman et al, 1996).…”

“…Methylglyoxal, a toxic byproduct of many physiological reactions (Chauhan & Madhubala, 2009;Kim et al, 2012;Korithoski et al, 2007;MacLean et al, 1998;Yadav et al, 2005), arises primarily through various metabolic pathways, e.g. increased glycolytic flux of triose phosphates, threonine/glycine catabolism and acetone breakdown .…”

“…For immunoblot analyses of SPI-2 and SPI-1 secreted proteins, Fmedium (Eswarappa et al, 2008) and LB with 0.3 M NaCl were used, respectively. Kinetic analyses of the STM3117 apoenzyme and holoenzyme with supplemented divalent metal ions were performed as described previously (Clugston et al, 2004, Korithoski et al, 2007. The method for determination of methylglyoxal in bacterial cells was adapted with modifications from Cordeiro et al Briefly, 100 ml exponential-phase culture (OD 600 0.5) corresponding to 0.01 g bacterial wet weight was used.…”

“…Elevated levels of mycobacteria-induced methylglyoxal and advanced glycation end-products in granulomatous lesions have been demonstrated to induce apoptosis of the resident macrophages as well as alter immune response genes (Rachman et al, 2006). The enhanced level of lactoylglutathione lyase (methylglyoxal detoxifying enzyme) has also been implicated in contributing to Streptococcus mutans aciduricity in dental plaques (Korithoski et al, 2007). Upregulation of either bacterial methylglyoxal-detoxifying genes or level of endogenous methylglyoxal during infection implies that pathogens exploit the methylglyoxal pathway differently to persist in host environs.…”