title: Bacterial profile of dentine caries and the impact of pH on bacterial population diversity.
abstract: Dental caries is caused by the release of organic acids from fermentative bacteria, which results in the dissolution of hydroxyapatite matrices of enamel and dentine. While low environmental pH is proposed to cause a shift in the consortium of oral bacteria, favouring the development of caries, the impact of this variable has been overlooked in microbial population studies. This study aimed to detail the zonal composition of the microbiota associated with carious dentine lesions with reference to pH. We used 454 sequencing of the 16S rRNA gene (V3-V4 region) to compare microbial communities in layers ranging in pH from 4.5-7.8 from 25 teeth with advanced dentine caries. Pyrosequencing of the amplicons yielded 449,762 sequences. Nine phyla, 97 genera and 409 species were identified from the quality-filtered, de-noised and chimera-free sequences. Among the microbiota associated with dentinal caries, the most abundant taxa included Lactobacillus sp., Prevotella sp., Atopobium sp., Olsenella sp. and Actinomyces sp. We found a disparity between microbial communities localised at acidic versus neutral pH strata. Acidic conditions were associated with low diversity microbial populations, with Lactobacillus species including L. fermentum, L. rhamnosus and L. crispatus, being prominent. In comparison, the distinctive species of a more diverse flora associated with neutral pH regions of carious lesions included Alloprevotella tanerrae, Leptothrix sp., Sphingomonas sp. and Streptococcus anginosus. While certain bacteria were affected by the pH gradient, we also found that ∼ 60% of the taxa associated with caries were present across the investigated pH range, representing a substantial core. We demonstrated that some bacterial species implicated in caries progression show selective clustering with respect to pH gradient, providing a basis for specific therapeutic strategies.
authors.affiliation: Institute of Dental Research, Westmead Centre for Oral Health and Westmead Millennium Institute, Westmead, Sydney, Australia; Department of Oral Biology, Faculty of Dentistry, University of Sydney, Sydney, Australia.
authors.forename: Nima
authors.initials: N
authors.lastname: Kianoush
authors.affiliation: Institute of Dental Research, Westmead Centre for Oral Health and Westmead Millennium Institute, Westmead, Sydney, Australia; Department of Oral Biology, Faculty of Dentistry, University of Sydney, Sydney, Australia.
authors.forename: Christina J
authors.initials: CJ
authors.lastname: Adler
authors.affiliation: Institute of Dental Research, Westmead Centre for Oral Health and Westmead Millennium Institute, Westmead, Sydney, Australia; Department of Oral Biology, Faculty of Dentistry, University of Sydney, Sydney, Australia.
authors.forename: Ky-Anh T
authors.initials: KA
authors.lastname: Nguyen
authors.affiliation: Institute of Dental Research, Westmead Centre for Oral Health and Westmead Millennium Institute, Westmead, Sydney, Australia.
authors.forename: Gina V
authors.initials: GV
authors.lastname: Browne
authors.affiliation: Institute of Dental Research, Westmead Centre for Oral Health and Westmead Millennium Institute, Westmead, Sydney, Australia.
authors.forename: Mary
authors.initials: M
authors.lastname: Simonian
authors.affiliation: Institute of Dental Research, Westmead Centre for Oral Health and Westmead Millennium Institute, Westmead, Sydney, Australia; Department of Oral Biology, Faculty of Dentistry, University of Sydney, Sydney, Australia.
authors.forename: Neil
authors.initials: N
authors.lastname: Hunter
mesh_terms: D001419:Bacteria; D044822:Biodiversity; D019295:Computational Biology; D004269:DNA, Bacterial; D003731:Dental Caries / Q000382:microbiology*; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D006863:Hydrogen-Ion Concentration; D054892:Metagenome; D064307:Microbiota; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S