Differential Response of Streptococcus mutans Towards Friend and Foe in Mixed-Species Cultures
ABSTRACT: In the oral biofilm, the mitis streptococci are among the first group of organisms to colonize the tooth surface. Their proliferation is thought to be an important factor required for antagonizing the growth of cariogenic species such as Streptococcus mutans. In this study, we used a 3-species mixed culture to demonstrate that another ubiquitous early colonizing species, Veillonella parvula, could greatly impact the competitive outcome of a mixed culture of S. mutans and S. gordonii. Transcriptome analysis further revealed that S. mutans responds differentially to its friend (V. parvula) and foe (S. gordonii). In the mixed culture with S. gordonii, all but one S. mutans sugar uptake and metabolic genes were down-regulated, while genes for alternative energy source utilization and H2O2 tolerance were up-regulated, resulting in a slower but persistent growth. In contrast, when cultured with V. parvula, S. mutans grew equally well or better than in monoculture and exhibited relatively few changes within its transcriptome. When V. parvula was introduced into the mixed culture of S. mutans and S. gordonii, it rescued the growth inhibition of S. mutans. In this 3-species environment, S. mutans increased the expression of genes required for the uptake and metabolism of minor sugars, while genes required for oxidative stress tolerance were down-regulated. We conclude that the major factors affecting the competition between S. mutans and S. gordonii are carbohydrate utilization and H2O2 resistance. The presence of V. parvula in the tri-species culture mitigates these two major factors and allows S. mutans to proliferate, despite the presence of S. gordonii. In this study, we used microarrays to investigate how S. mutans responds to different species. S. mutans was grown as either monospecies, dual-species cultures with S. gordonii or Veillonella, or tri-species cultures with S. gordonii and Veillonella. The transcriptional profile of the whole genome was examined with microarray.
Project description:In the oral biofilm, the mitis streptococci are among the first group of organisms to colonize the tooth surface. Their proliferation is thought to be an important factor required for antagonizing the growth of cariogenic species such as Streptococcus mutans. In this study, we used a 3-species mixed culture to demonstrate that another ubiquitous early colonizing species, Veillonella parvula, could greatly impact the competitive outcome of a mixed culture of S. mutans and S. gordonii. Transcriptome analysis further revealed that S. mutans responds differentially to its friend (V. parvula) and foe (S. gordonii). In the mixed culture with S. gordonii, all but one S. mutans sugar uptake and metabolic genes were down-regulated, while genes for alternative energy source utilization and H2O2 tolerance were up-regulated, resulting in a slower but persistent growth. In contrast, when cultured with V. parvula, S. mutans grew equally well or better than in monoculture and exhibited relatively few changes within its transcriptome. When V. parvula was introduced into the mixed culture of S. mutans and S. gordonii, it rescued the growth inhibition of S. mutans. In this 3-species environment, S. mutans increased the expression of genes required for the uptake and metabolism of minor sugars, while genes required for oxidative stress tolerance were down-regulated. We conclude that the major factors affecting the competition between S. mutans and S. gordonii are carbohydrate utilization and H2O2 resistance. The presence of V. parvula in the tri-species culture mitigates these two major factors and allows S. mutans to proliferate, despite the presence of S. gordonii. Overall design: In this study, we used microarrays to investigate how S. mutans responds to different species. S. mutans was grown as either monospecies, dual-species cultures with S. gordonii or Veillonella, or tri-species cultures with S. gordonii and Veillonella. The transcriptional profile of the whole genome was examined with microarray.
Project description:Streptococcus mutans, the organism most frequently associated with the development of dental caries, is able to utilize a diverse array of carbohydrates for energy metabolism. One such molecule is trehalose, a disaccharide common in human foods, which has recently been implicated in enhancing the virulence of epidemic strains of the pathogen, Clostridium difficile. In this study, deletion mutants of all three genes in the putative S. mutans trehalose utilization operon were characterized and shown to be required for wild-type levels of growth when trehalose was the only carbohydrate source provided. Interestingly, the TreR transcriptional regulator appeared to be critical for responding to oxidative stress, and for mounting a protective stress tolerance response following growth at moderately acidic pH. RNAseq of a treR deletion mutant suggested that in S. mutans, TreR acts as a trehalose-sensing activator of transcription of the tre operon, rather than a repressor, as described in other species. In addition, deletion of treR caused the down-regulation of a number of genes involved in genetic competence and bacteriocin production, supporting results of a recent study linking trehalose and the S. mutans competence pathways. Finally, deletion of treR compromised the ability of S. mutans to inhibit the growth of the competing species, Streptococcus gordonii and Lactococcus lactis. Taken together, this study solidifies the role of the S. mutans tre operon in trehalose utilization and suggests novel functions for the TreR regulator, including roles in stress response and competitive fitness. Overall design: Transcriptional profiling was performed using RNA extracted from cultures of S. mutans parent strain UA159 and the ∆treR derivative grown in tryptone-yeast extract medium supplemented with either glucose, galactose or trehalose.
Project description:Polymicrobial biofilms are of large medical importance, but little is known about their physiology and the underlying interspecies interactions. Here we studied two human pathogens, the opportunistic fungus Candida albicans and the caries promoting bacterium Streptococcus mutans. Both species formed biofilms in monoculture, with C. albicans growing mainly in the virulence-associated hyphae form, and S. mutans forming a thick layer of extracellular polymeric substances (EPS). Biofilm growth was enhanced in dual-species biofilms, which reached twice the biomass of monospecies biofilms and higher cell numbers of both S. mutans and C. albicans. EPS production by S. mutans was strongly suppressed in dual-species biofilms. Virulence traits of S. mutans, e.g. genetic competence, biofilm formation and bacteriocin synthesis are controlled by quorum sensing through activation of the alternative sigma factor SigX. SigX is induced by the pheromones CSP (competence stimulating factor) or XIP (sigX inducing peptide). Strong induction of sigX was observed in dual species biofilms indicated by fluorescence of a reporter strain for the sigX promoter, S. mutans PcomX-gfp, as well as by qRT-PCR of comX. The peak of sigX expression occurred after 10 h of biofilm growth. Conditioned media from mixed biofilms but not from C. albicans or S. mutans cultivated alone activated sigX in the reporter strain. Deletion mutants for the comC and comS genes encoding the precursors of CSP and XIP, respectively, were constructed. Conditioned media from mixed biofilms with S. mutans DcomS were unable to induce sigX in the reporter strain, while deletion of comC had no effect. These data show that synthesis of XIP was induced in S. mutans by coculture with C. albicans. Transcriptome analysis of S. mutans in single and mixed biofilms confirmed strong induction of comS, sigX, and the downstream late competence genes in dual-species biofilms. Among the late competence genes, fratricins were discovered for the first time. The comCDE operon and bacteriocin related genes were also induced, but much weaker. Genes related to oxidative stress, chaperones and glycosyltransferase genes required for EPS synthesis from sucrose were down-regulated, while glycogen synthesis genes were up-regulated, indicating that S. mutans was protected from oxidative stress and provided with excess sugar for storage polymer synthesis in mixed biofilms. The data show that in dual-species biofilms, C. albicans improves growth of S. mutans, suppresses its EPS formation and induces the complete quorum sensing signalling system, thus fundamentally changing the virulence properties of the caries pathogen, including its potential interactions with other members of the polymicrobial dental plaque community. Dual-species biofilms of S. mutans and C. albicans and single-species biofilms of S. mutans were cultivated in 24-well microtitre plates in YNBB medium. Transcriptional profiles of S. mutans in single- and dual-species biofilms were analysed at early (6 h) and late (10 h) logarithmic phase of the biofilm growth, as well as after 24 h when biofilms entered stationary phase. Transcriptional profiles of S. mutans grown in the dual-species biofilms were compared to profiles obtained for single-species biofilm from the same time point. Three biological and one to two technical replicas were used in the microarray study. RNA samples were labeled with Cy3 or Cy5 using the ULS fluorescent labeling kit (Kreatech, Germany). Seven hundred nanograms of Cy3 or Cy5 labeled RNA after fragmentation were hybridized to the microarray at 65°C for 17 h using the Agilent hybridization chamber according to the manufacturer's instructions. The arrays were scanned using the Agilent DNA microarray scanner and the raw data were extracted using Agilent Feature Extraction software (v. 10.7).
Project description:Investigation of whole genome gene expression levels of P. gingivalis W83, F. nucleatum DSMZ 25586, S. sanguinis SK36, A. actinomycetemcomitans HK1651, S. mutans UA159 in an 24 h old culture. Additionally, whole genome gene expression level changes of S. mutans UA159 biofilm cells after co-cultivation with S. mitis ATCC 11843 were compared to its single species biofilm growth after 24 h. Aim: Demonstration of the usefulness of a five-species gene expression array. Multiple probes per gene enabled identification of single inter-species cross-hybridizing probes. The deletion of such probes lead almost not to the deletion of the whole gene. This was investigated and confirmed by a two-species biofilm expression analysis: The here described array was used for the identification of genes of S. mutans influenced by the presence of S. mitis. Materials and Methods: P. gingivalis W83, F. nucleatum DSMZ 25586, S. sanguinis SK36, A. actinomycetemcomitans HK1651,and S. mutans UA159 were grown in CDM/succrose or artificial saliva/galactose in a single-species culture for 24 h anaerobically resulting in biofilm structures or monolayers. Total RNA was isolated and used for microarray analysis. Probes were analysed for the presence of biological false positive signals caused by cross-hybridizing probes of one of the other species presented on the chip. Further, a simple procedure was developed for automatical identification and deletion of false positive signals caused by washing artefacts, resulting in a more reliable outcome. In the case of the S. mutans/S. mitis mixed-species biofilm, both species were cultured together for 24 h like previously described. The found gene regulations were verified by RT-PCR. Results: Experiments with cDNA from 24 h old single-species cultures allowed the identification of cross-species hybridizing probes on the array, which can be eliminated in mixed-species experimental settings without the need to exclude the whole genes from the analysis. Between 69 % and almost 100 % represented genomes on this array were found actively transcribed under the mono-species monolayer and biofilm conditions used here. S. mutans / S. mitis co-culture: Physiological investigations revealed an increase in S. mutans biofilm mass with a decrease in pH-value under the influence of S. mitis, thereby confirming previously published data. A stringent fold change cut-off of 2 (p<0.05) identified 19 S. mutans transcripts with increased abundance, and 11 with decreased abundance compared to a S. mutans mono-species biofilm. Many of the genes have previously been found differentially regulated under general and acid stress, thereby confirming the value of this array. Conclusions: Taken together, this new array allows transcriptome studies on multi-species oral biofilm interactions and could become an important asset in future oral biofilm and inhibitor/therapy studies. The chip study used pooled total RNA recovered from three biologically independent mono-species biofilms or adherent cells/monolayers of P. gingivalis W83, F. nucleatum DSMZ 25586, S. sanguinis SK36, A. actinomycetemcomitans HK1651, and S. mutans UA159. In the case of gene expression analysis of S. mutans/S.mitis biofilm structures compared to the single species biofilm of S. mutans three separate single and three separate two-species biofilm cultures were analysed. Each chip measured the expression level of all together 10186 genes (1883 genes of P. gingivalis W83, 1964 genes of F. nucleatum DSMZ 25586, 2244 genes of S. sanguinis SK36, 2168 genes of A. actinomycetemcomitans HK1651, 1927 genes of S. mutans UA159) with up to thirteen 60-mer probes per gene and with a three-fold technical redundancy.
Project description:We performed comparative analysis of transcriptomes of S. mutans in single biofilms and in mixed-biofilms with A. actinomycetemcomitans. We also compared the transcriptomic profiles of A. actinomycetemcomitans in single biofilms and A. actinomycetemcomitans in mixed biofilms with S. mutans. Finally we looked at the changes in gene expression in both organisms in time. Overall design: RNAseq of single species biofilms (S. mutans, A.act.) - 8 and 24 h, dual-species biofilms (S.mutans with A.act.) - 4, 6, 8,10, 12, and 24 h. All in duplicate. Using Illumina HiSeq.
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.
Project description:Recent studies have shown that the transcriptional landscape of the pleiomorphic fungus Candida albicans is highly dependent upon growth conditions. Here using a dual RNA-seq approach we identified 299 C. albicans and 72 Streptococcus gordonii genes that were either up- or down-regulated specifically as a result of co-culturing these human oral cavity microorganisms. Seventy five C. albicans genes involved in responses to chemical stimuli, regulation, homeostasis, protein modification and cell cycle were statistically (P ≤0.05) upregulated, while 36 genes mainly involved in transport and translation were down-regulated. Upregulation of filamentation-associated TEC1 and FGR42 genes, and of ALS1 adhesin gene, concurred with previous evidence that the C. albicans yeast to hypha transition is promoted by S. gordonii. Increased expression of genes required for arginine biosynthesis in C. albicans was potentially indicative of a novel oxidative stress response. The transcriptional response of S. gordonii to C. albicans was less dramatic, with only eight S. gordonii genes significantly (P ≤0.05) up-regulated ≥ twofold (glpK, rplO, celB, rplN, rplB, rpsE, ciaR, and gat). The expression patterns suggest that signals from S. gordonii cause a positive filamentation response in C. albicans, while S. gordonii appears to be transcriptionally less influenced by C. albicans. Five Samples; Sample 1 - Candida albicans cells grown in hypha inducing conditions for two hours; Sample 2 - Candida albicans cells grown in hypha-inducing conditions for two hours before co-culture with Streptococcus gordonii cells for one hour in a 2:1 rato; Sample 3 - Candida albicans cells grown in hypha-inducing conditions for two hours before culture in Streptococcus gordonii media for one hour; Sample 4 - Candida albicans cells grown in hypha inducing conditions for two hours, filtered to remove Candida albicans cells and media added to Streptococcus gordonii cells for one hour; Sample 5 - Streptococcus gordonii cells alone for one hour. All samples extracted and sequenced in biological triplicate using Illumina HiSeq2500. Samples 1, 2 and 3 aligned to the reference genome for Candida albicans and Samples 2, 4 and 5 aligned to the reference genome for Streptococcus gordonii.
Project description:As a resident of the oral cavity, Streptococcus mutans must withstand a variety of stresses, including oxidative stress. Previously, we reported the identification of two Spx homologues (SpxA1 and SpxA2) in Streptococcus mutans that appear critical in the ability of the microbe to tolerate oxidative stresses; SpxA1 was shown to play a primary role in activation of detoxification strategies whereas SpxA2 served as a secondary activator. Here, we used RNA deep sequencing (RNA-Seq) to examine the transcriptional changes associated with H2O2 stress in the parent S. mutans strain UA159 and to compare the peroxide-stress transcriptome of UA159 with its Δspx derivatives. The transcriptome data confirmed the relationship between SpxA1 and genes typically associated with oxidative stress responses, but also identified new genes and metabolic pathways that are activated during peroxide stress, also in an SpxA1-dependent manner. Overall design: Transcriptional profiling of Streptococcus mutans UA159 wild-type strain was performed before and after 5 minutes exposure to 0.5mM H2O2, and of mutant strains ∆spxA1, ∆spxA2, ∆spxA1/∆spxA2 after the same H2O2 exposure. RNA was extracted from S. mutans cells after the desired treament using standard methods. Following Dnase treatment and enrichment for mRNA, Deep RNA sequencing was performed by the University of Rochester Genomics Research Center using the Illumina platform
Project description:Transcriptional profiling was utilized to define the biological pathways of gingival epithelial cells modulated by mono- and complex co-culture with oral commensal S. gordonii and pathogenic P. gingivalis. We used microarrays to detail the global programme of gene expression underlying infection and identified distinct classes of up- and down-regulated genes during this process. Keywords: infection state Overall design: Gingival epithelial HIGK cells were sham infected (CTRL) and infected with either the oral commensal S. gordonii (Sg) or the pathogenic P. gingivalis (Pg) as well as co-cultured in mixed cultures of Sg and Pg (Sg+Pg). These samples were hybridized to Affymetrix microarrays. Understanding how host cells have adapted to commensals, and how barrier cells respond to limit their impact, provides a mechanistic biological basis of health in the mixed bacterial-human ecosystem of the oral cavity and provides insight on how the degree of complexity of a microbiome influences this balance.