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Expression analysis of Streptococcus mutans UA159 under Hyperosmotic stress environment

ABSTRACT: Oral streptococci metabolize carbohydrate to produce organic acids, which not only decrease the environmental pH, but also increase osmolality of dental plaque fluid due to tooth demineralization and consequent calcium and phosphate accumulation. Despite these unfavorable environmental changes, the bacteria continue to thrive. The aim of this study was to obtain a global view on strategies taken by Streptococcus mutans to deal with physiologically relevant elevated osmolality, and perseveres within a cariogenic dental plaque. We investigated phenotypic change of S. mutans biofilm upon hyperosmotic challenge. We found that the hyperosmotic condition was able to initiate S. mutans biofilm dispersal by reducing both microbial content and extracellular polysaccharides matrix. We then used whole-genome microarray with quantitative RT-PCR validation to systemically investigate the underlying molecular machineries of this bacterium in response to the hyperosmotic stimuli. Among those identified 40 deferentially regulated genes, down-regulation of gtfB and comC were believed to be responsible for the observed biofilm dispersal. Further analysis of microarray data showed significant up-regulation of genes and pathways involved in carbohydrate metabolism. Specific genes involved in heat shock response and acid tolerance were also upregulated, indicating potential cross-talk between hyperosmotic and other environmental stress. Hyperosmotic condition induces significant stress response on S. mutans at both phenotypic and transcriptomic levels. In the meantime, it may take full advantage of these environmental stimuli to better fit the fluctuating environments within oral cavity, and thus emerges as numeric-predominant bacterium under cariogenic conditions.

ORGANISM(S): Streptococcus mutans UA159

PROVIDER: GSE47170 | GEO | 2013/08/31

SECONDARY ACCESSION(S): PRJNA204974

REPOSITORIES: GEO

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Project description:Oral streptococci metabolize carbohydrate to produce organic acids, not only decrease the environmental pH, but also increase osmolality of dental plaque fluid due to tooth demineralization and consequent calcium and phosphate accumulation. Thus, to persevere in the dental plaque, acidogenic bacteria should evolve sophisticated molecular machineries to counter the detrimental effect of elevated osmolality. This study was aimed to obtain a global view on strategies taken by streptococcus mutans to deal with physiologically relevant elevated osmolality, and preserves within a cariogenic dental plaque. We investigated phenotypic change of S. mutans biofilm upon sub-lethal level of hyperosmotic challenge. We found that hyperosmotic condition was able to initiate S. mutans biofilm dispersal by reducing both microbial content and extracellular polysaccharides matrix. We then used DNA microarray with qPCR validation to systemically investigate the underlying molecular machinery of this bacteria in response to hyperosmotic stimuli. Among those identified 50 differentially regulated genes, down-regulation of gtfB and comC were believed to be responsible for the observed biofilm dispersal. Further analysis of microarray data showed significant up-regulation of genes and pathways involved in carbohydrates metabolism. Specific genes involved in heat shock response and acid tolerance were also upregulated, indicating potential cross-talk between hyperosmotic and other environmental stress. Based on the data obtained in this study, we believe that although hyperosmotic condition may induce significant stress response on S. mutans, this cariogenic bacterium has evolved sophisticated molecular machineries to counter those elicited detrimental effects. In the meantime, it will take full advantage of these environmental stimuli to better fit the fluctuating environments within oral cavity, and thus emerge as numeric-predominant bacteria under cariogenic conditions. A six-chip study using total RNA recovered from mid-logarithmic phase of S. mutans UA159 from three separate cultures of strains submitted for 15 minutes to hyperosmotic stimuli (0.4M NaCl) and three separate cultures of strains kept under no stress condition.

Project description:Lysine malonylation is an evolutionarily conserved PTM from bacteria to mammals and involves malonyl-coenzyme (CoA) as a cofactor. Since the malonyl group has an acidic carboxylic group under physiological pH, malonylated lysine is negatively charged, which might impact on protein function and enzymatic activities. Like other short-chain acyl-CoAs, malonyl-CoA can be synthesized from its corresponding short-chain acyl salt, malonate, catalyzed by malonyl-CoA synthetase (Witkowski et al., 2011). In addition, malonyl-CoA can be produced during the carboxylation of acetyl-CoA by acetyl-CoA carboxylase (ACC), the carboxylation of acetyl-CoA by propionyl-CoA carboxylase, and the β-oxidation of old-chain-length dicarboxylic acids (Peng et al., 2011). Most studies on Kmal have been performed in mammalian systems and identified thousands of malonylated sites, revealing its role in the progress of diseases like type 2 diabetes, schizophrenia, and cardiac hypertrophy (Du et al., 2015; Smith et al., 2022; Wu et al., 2022). There has been increasing interest in dissecting the regulatory roles of Kmal in several bacterial species, such as Escherichia coli (Qian et al., 2016), Bacillus amyloliquefaciens (Fan et al., 2017), Mycobacterium tuberculosis (Bi et al., 2022), and Staphylococcus aureus (Shi et al., 2021), which demonstrates that Kmal exists in diverse prokaryotic organisms and participates in the regulation of various physiological processes. Even so, whether Kmal exists and affects protein functions in streptococci remains unknown. S. mutans is considered to be the most prevalent and cariogenic species in active carious lesions of humans, residing primarily in dental plaque, which is a biofilm that forms on the tooth surfaces. During the past decades, studies of S. mutans have focused on revealing the molecular mechanisms underlying the robust biofilm formation on tooth surfaces, the metabolism of a wide variety of carbohydrates obtained from the host diet, and the adaption of numerous environmental challenges (Lemos et al., 2019). Several studies have been performed to reveal the roles of PTMs in biofilm and cariogenic virulence. Wang et al. found that the phosphorylation of VicR could inhibit the expression of the glucosyltransferases gtfBC, thereby reducing the synthesis of extracellular polysaccharides (EPS), the major component of cariogenic biofilm (Wang et al., 2021). Acetylome study on the S. mutans depicted that acetylated substrates were globally altered in the biofilm state compared to the planktonic state, and the acetylated GtfBC showed decreased activities (Lei et al., 2021; Ma et al., 2021). Our previous study revealed that the S-glutathionylation of a thioredoxin-like protein is important for interspecies competition and cariogenicity of S. mutans(Li et al., 2020). These results suggest that various PTM types exist in S. mutans and participate in diverse physiological processes. The genome of S. mutans UA159 codes an acetyl coenzyme A carboxylase (ACC), which could synthesize malonyl-CoA through the carboxylation of acetyl-CoA (Ajdić et al., 2002), implying the existence of malonylation in this bacterium. Therefore, this study aimed to confirm the existence of Kmal in S. mutans and identify the malonylated sites globally. The present findings provide a systematic view of the functional roles of Kmal in various metabolic pathways of S. mutans.

Project description:Candida albicans, a major opportunistic fungal pathogen is frequently found together with Streptococcus mutans in dental biofilms associated with severe childhood tooth-decay, a prevalent pediatric oral disease. Previous studies have demonstrated that S. mutans and C. albicans synergizes virulence of plaque-biofilms in vivo. However, the nature of this bacterial-fungal relationship in this cross-kingdom biofilm remains largely uncharacterized. Using iTRAQ based quantitative proteomics, we found that proteins associated with carbohydrate metabolism such as alpha-1,4 glucan phosphorylase, Hexokinase-2, Isocitrate lyase and malate synthase were significantly upregulated in C. albicans in the mixed-species biofilms (P<0.05). C. albicans proteins associated with growth/morphogenesis such as pH-responsive protein-2, Fma1p and Hsp21 were also induced. Conversely, S. mutans proteins in the tricarboxylic acid cycle such as citrate synthase and in the pentose phosphate pathway such as Ribose-5-phosphate isomerase A as well as proteins associated with sugar transport systems were upregulated indicating enhanced carbohydrate metabolism. Interestingly mixed-species biofilm microenvironment had a lower pH than S. mutans single-species biofilms. This observation was supported by proteomics, wherein proteins associated with lactate and formate assimilation such as Glyoxalase and putative NADPH-dependent methylglyoxal reductase proteins were significantly upregulated in the mixed-species biofilms (P<0.05). Furthermore, we unexpectedly found that S. mutans derived glucosyltransferase B (GtfB), responsible for co-adhesion via glucans, can also contribute to C. albicans growth and carbohydrate metabolism by providing glucose and fructose from sucrose breakdown. These findings demonstrate synergistic bacterial-fungal interactions within mixed-species biofilms and a novel GtfB cross-feeding role. Taken together, quantitative proteomics provides new insights into this virulent cross-kingdom oral biofilm.

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Expression analysis of Streptococcus mutans UA159 under Hyperosmotic stress environment

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