Relative abundance of bacterial taxa in saliva samples at the class level.

<p>The sample order corresponds to the increase in <i>Candida</i> load in the samples (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042770#pone.0042770.s006" target="_blank">Table S2</a>). The <i>Candida</i> load was measured as proportion of ITS gene over 16S gene abundance by qPCR. Increase in <i>Candida</i> load correlated positively with reads classified as Bacilli (<i>p</i> = 0.013; Spearman’s rho 0.274), while class Bacteroidia (<i>p</i> = 0.001; Spearman’s rho −0.360), Flavobacteria (<i>p</i> = 0.003; Spearman’s rho −0.322), Fusobacteria (<i>p</i> = 0.012; Spearman’s rho −0.275) correlated negatively with the <i>Candida</i> load (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042770#pone.0042770.s001" target="_blank">Figure S1</a>).</p

Diversity statistics by <i>Candida</i> load in dentate subjects.

<p>Diversity statistics by <i>Candida</i> load (low (N = 8), medium (N = 12), high (N = 14)) in dentate subjects as boxplots of: A) OTUs per sample, B) Dominance Index and C) Shannon Diversity Index. Each box shows the median, quartiles, and outliers (circles). Connector connects statistically significantly different groups (<i>p</i><0.05; Mann-Whitney test).</p

Diversity statistics of salivary microbiomes by <i>Candida</i> load.

<p>Diversity statistics of salivary microbiomes as: A) Dominance Index and B) Shannon Diversity Index by log10 <i>Candida</i> ITS/16S gene. <i>Candida</i> load correlated positively with the Dominance Index (<i>p</i><0.001; Spearman’s rho 0.388) and negatively with the Shannon Diversity Index (<i>p</i><0.001; Spearman’s rho −0.403).</p

Salivary microbiome data by <i>Candida</i> load.

<p>Salivary microbiome data is plotted as OTU-based Principal Component Analysis (PCA) plot by <i>Candida</i> load in A) all subjects (N = 82) and in B) dentate subjects only (N = 34). Samples are colored by <i>Candida</i> load: green - low, blue - medium and red - high <i>Candida</i> load. Arrow indicates the main PC direction between low and high <i>Candida</i> load samples.</p

Phyla composition of individual 1 per sample site and DNA extraction method.

<p>Samples extracted with Agowa and Qiagen showed a significant higher proportion of Actinobacteria and Firmicutes and a lower proportion of Bacteriodetes, compared to Epicentre and Mobio, especially in the oropharyngeal and saliva samples for all 4 individuals. Note that nasopharyngeal samples from all four individuals isolated with Epicentre failed to give results.</p

Principal component analyses (PCA) of the microbiota profiles and Principal Coordinate of Analyses (PcoA) plot of the weighted and unweighted UniFrac average distance per site and DNA extraction method.

<p><i>a</i>. Principal component analyses (PCA) of the microbiota profiles of the nares and nasopharynx depicted per dilution and DNA extraction method. Depicted in colors are 16S DNA levels (blue = ≥1 pg/µl, green = <1 pg/µl). Depicted in characters are the DNA extraction methods (A = Agowa, E = Epicentre, Q = qiagen, M = Mobio). Clustering of the samples is according to DNA level and DNA extraction method. Differences in template concentration were due to differences in DNA extraction efficiency between used methods and effects of template concentration on microbiota analyses were therefore fully tied to DNA extraction effects. <i>b</i>.PcoA plot of the weighted UniFrac. Shown in colored circles are the DNA extraction methods (yellow = Epicentre, red = Mobio, blue = Qiagen and green = Agowa). The abbreviations represent the site of sampling (NP = nasopharynx, N = nares, OP = oropharynx, SA = saliva). Clear clustering per site of sampling was observed with saliva and oropharynx distant from nares and nasopharynx samples. For the oropharynx and saliva clusters significant sub-clustering per DNA extraction method was seen with clusters of Epicentre and Mobio, distant from Agowa and Qiagen clusters. DNA extraction method in these high density sites even introduced a larger distance in microbiota profile than origin of the sample (saliva or oropharynx). <i>c</i>. PCoA plot of the unweighted UniFrac as described above. Clear clustering per site of sampling was observed with saliva and oropharynx distant from nares and nasopharynx samples, and also between saliva and oropharynx. For the nares and nasopharynx clusters significant sub-clustering per DNA extraction method was seen with clusters of Agowa, Qiagen and Epicentre distant from Mobio. Both weighted and unweighted UniFrac analysis of sequence data revealed distinct clustering of saliva and oropharyngeal separate from nares and nasopharynx samples, reflecting unique differences in microbiota composition between these sites (Amova, p<0.001, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032942#pone.0032942.s004" target="_blank">Figure S4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032942#pone.0032942.s005" target="_blank">S5</a>).</p

Sequence characteristics of undiluted and serially diluted saliva (1 individual), isolated with the Agowa extraction method.

<p>A clear increase in unique sequences, unclassified bacteria and Shannon diversity index was seen in dilution 3 (10⁵ bacteria/ml). Undiluted = undiluted saliva, 1 = dilution 1, 10⁷ bacteria/ml, 2 = dilution 2, 10⁶ bacteria/ml and 3 = dilution 3, 10⁵ bacteria/ml.</p>*<p>Using a moving window 50 bp long to check that the average quality score over the region does not drop below 35 (using the qual file).</p>§<p>The <b>coverage</b> calculator returns Good's coverage for an OTU definition.</p

Average relative abundance of the 6 main taxa in undiluted saliva and dilutions 1 to 3 (10⁷ to 10⁵ bacteria per ml, respectively).

<p>Shown in error bars is the standard deviation per dilution indicative of the variation between DNA extraction methods. We used ANOVA statistics to test for significant differences. Dilution 3 shows a significant increase in Proteobacteria (p<0.001, mean 26,11% and 3.6%, SD 17.5 and 2.5% respectively) and a significant decrease in Bacteroidetes (p<0.001, mean 18.99% and 43.1% respectively) compared to the undiluted saliva samples. By diluting the sample up to 10⁵ bacteria per ml an increase in Firmicutes, mostly <i>Veilonella</i>, was observed, and a decrease in Bacteroidetes, mostly <i>Prevotella</i>.</p

Microbiota composition and Principal Coordinate of Analyses for serially diluted saliva.

<p><i>a</i>. Microbiota composition for undiluted and serially diluted saliva of individual 1 isolated with the Agowa method. For undiluted saliva, the dilutions and the PCR blank, relative abundance of the genera expressed in percentages are shown on the y-axes. The legend shows the 30 most abundant taxa and genera found in colors. Microbiota composition starts to deviate from the original sample at dilution 3 (10⁵ bacteria/ml). In dilutions 1 and 2 low abundant genera seemed to increase in abundance, while high abundant genera decrease in abundance. <i>b</i>. Unweighted UniFrac Principal Coordinate Analyses plot of undiluted and serially diluted saliva isolated with four DNA extraction methods. Great overlap in sequence representation was seen between undiluted samples and samples diluted up to dilution 2 (10⁶ bacteria per ml) for all DNA extraction methods except for Mobio. Dilution 3 samples (10⁵ bacteria per ml) are deviating from the original sample. DNA extraction methods are depicted in characters (E = Epicentre, M = Mobio, Q = Qiagen and A = Agowa). The dilutions are depicted in symbols as shown in the legend. Undiluted = undiluted saliva, 1 = dilution 1, 10⁷ bacteria/ml, 2 = dilution 2, 10⁶ bacteria/ml and 3 = dilution 3, 10⁵ bacteria/ml.</p

Data_Sheet_1.XLSX

<p>Background: The oral cavity harbors a complex microbial ecosystem, intimately related to oral health and disease. The use of polyol-sweetened gum is believed to benefit oral health through stimulation of salivary flow and impacting oral pathogenic bacteria. Maltitol is often used as sweetener in food products. This study aimed to establish the in vivo effects of frequent consumption of maltitol-sweetened chewing gum on the dental plaque microbiota in healthy volunteers and to establish the cellular and molecular effects by in vitro cultivation and transcriptional analysis.</p><p>Results: An intervention study was performed in 153 volunteers, randomly assigned to three groups (www.trialregister.nl; NTR4165). One group was requested to use maltitol gum five times daily, one group used gum-base, and the third group did not use chewing gum. At day 0 and day 28, 24 h-accumulated supragingival plaque was collected at the lingual sites of the lower jaw and the buccal sites of the upper jaw and analyzed by 16S ribosomal rRNA gene sequencing. At day 42, 2 weeks after completion of the study, lower-jaw samples were collected and analyzed. The upper buccal plaque microbiota composition had lower bacterial levels and higher relative abundances of (facultative) aerobic species compared to the lower lingual sites. There was no difference in bacterial community structure between any of the three study groups (PERMANOVA). Significant lower abundance of several bacterial phylotypes was found in maltitol gum group compared to the gum-base group, including Actinomyces massiliensis HOT 852 and Lautropia mirabilis HOT 022. Cultivation studies confirmed growth inhibition of A. massiliensis and A. johnsonii by maltitol at levels of 1% and higher. Transcriptome analysis of A. massiliensis revealed that exposure to maltitol resulted in changes in the expression of genes linked to osmoregulation, biofilm formation, and central carbon metabolism.</p><p>Conclusion: The results showed that chewing itself only marginally impacted the plaque microbiota composition. Use of maltitol-sweetened gum lowered abundance of several bacterial species. Importantly, the species impacted play a key role in the early formation of dental biofilms. Further studies are required to establish if frequent use of maltitol gum impacts early dental-plaque biofilm development.</p