Streptococcus mutans copes with heat stress by multiple transcriptional regulons modulating virulence and energy metabolism

Abstract

Dental caries is closely associated with the virulence of Streptococcus mutans. The virulence expression of S. mutans is linked to its stress adaptation to the changes in the oral environment.In this work we used whole-genome microarrays to profile the dynamic transcriptomic responses of S. mutans during physiological heat stress. In addition, we evaluated the phenotypic changes, including, eDNA release, initial biofilm formation, extracellular polysaccharides generation, acid production/acid tolerance, and ATP turnover of S. mutans during heat stress. There were distinct patterns observed in the way that S. mutans responded to heat stress that included 66 transcription factors for the expression of functional genes being differentially expressed. Especially, response regulators of two component systems (TCSs), the repressors of heat shock proteins and regulators involved in sugar transporting and metabolism co-ordinated to enhance the cell's survival and energy generation against heat stress in S. mutans.Streptococcus mutans, the major etiological agent in dental caries, colonizes the multispecies microbial biofilms that adhere to tooth surfaces 1,2 . Sophisticated environmental adaptation is critical for the survival and prevalence of S. mutans in the oral cavity, which is a dynamic habitat subject to a wide range of harsh and rapidly changing physiological conditions, including extreme acidity, fluctuation of nutrients, osmotic stress, shifts in temperature and reactive oxygen species, etc 3 .The adaptation mechanism to heat stress in bacteria is one of the most conserved biological stress responses in bacteria as they adapt to changing environments 4 . Temperature shift signals feed into the transcriptional regulatory systems of bacteria, which affects the physiological changes that enable organisms to adapt and survive 4 . Within the process there are the phases of recognition and adjustment that are coordinated by enzyme and gene level regulation 5 . Alternative sigma factors play an important role in the adaptation process, which is mediated by complex regulatory networks 6 . The Escherichia coli heat shock response is highly specific and mediated by members of the sigma 32 regulon through two

Gsy, a novel glucansucrase from Leuconostoc mesenteroides, mediates the formation of cell aggregates in response to oxidative stress

“…Total RNA extraction and transcription analysis was performed as previously described35. Briefly, RNA was extracted and purified using RNeasy Mini kits (Qiagen) and digested with RNase-free DNase I.…”

“…Agarose electrophoresis was then used to determine the integrity and quality of the RNA. For Quantitative reverse-transcription PCR analysis, gene-specific primers (Table 1) were used, and first-strand cDNAs were synthesized using the FastQuant RT kit with gDNase (Tiangen) according to the manufacturer’s instructions (a none RT control was done as described previously35 to ensure to absence of gDNA). Each PCR reagent (25 μL) contained SuperReal premix Plus (Tiangen), cDNA samples and forward and reverse gene-specific primers (10 μM each).…”

Remodeling of the Streptococcus mutans proteome in response to LrgAB and external stresses

“…Multiple ABC transporters, including OpuBa, SMU_922, SMU_1194, and SMU_1568 also showed significantly ( p < 0.05) increased abundance. Major functional categories that were uniquely upregulated in response to heat stress included energy metabolism and PTSs, whereas DNA metabolism and protein synthesis-related proteins showed significantly decreased abundance, suggesting possible metabolic rewiring for production of extra energy (ATP) to cope with this stress 32 , 33 . It is also notable that among the heat-shock related molecular chaperones and proteases, only DnaK and Clp-like proteases (SMU_956 and SMU_2029) showed increased abundance uniquely in response to heat stress, suggesting that these proteins may be especially important for S .…”

Dual-light photodynamic therapy administered daily provides a sustained antibacterial effect on biofilm and preventsStreptococcus mutansadaptation

“…Similar early responses in the S. mutans expression profile can be seen in other heat responsive genes, such as grpE, dnaK and fruR. Eventually, the upregulation of clpE and clpP aid the survival of the cells in the harsh conditions, including increased oxidative stress [23]. Antibacterial blue light has also been shown to alter the gene expression of S. mutans , upregulating several genes such as gtfB, brp, smu630, and comDE, but has also been shown to increase the susceptibility of bacteria to ROS [24], which can further explain not only the adaptive mechanisms but also the additive bactericidal effect of the simultaneous use of aBL and aPDT.…”

“…Prokaryotic cells contain the same heat shock proteins as eukaryotic cells, enabling bacteria to cope against hostile environments. Heat stress has been shown to cause a distinct response in the S. mutans expression profile of multiple regulator and other functional genes[22,23]. The extracellular matrix architectural structure and the cells ability to bind are impaired due to heat.…”