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Chapter 24 : The Streptococcus-Veillonella Community: How Genome Sequencing Aids Our Understanding of Interspecies Interaction
Category: Genomics and Bioinformatics
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This chapter integrates unpublished data with the published reports on the synergism between veillonellae and streptococci. It speculates on how the genome sequence of veillonellae will help one understand its biology and potential role in the pathogenicity of the dental biofilm community. It was discovered that hydrogen peroxide (H2O2) resistance in Streptococcus mutans was increased 100 to 1,000-fold over monospecies culture in cocultures with Veillonella sp. strain PK1910. This chapter focuses on some important findings from the Veillonella sp. strain PK1910 genome. In the 1964 description of Veillonellasp. by Rogosa, the species V. alcalescens was distinguished from V. parvula by the ability to decompose H2O2. In the 1982 revision of the species, the former subspecies in V. alcalescens were classified as three species: V. ratti, V. criceti, and V. dispar. Veillonella species are among the most prevalent early colonizers of oral biofilm. In-depth investigations on the mechanism of interactions of veillonellae with other oral microbial species will contribute significantly to one's overall understanding of the ecology of oral biofilms in the human host. Different from a metagenomics approach, metatranscriptomics focuses on community member functions at a particular time under a particular condition.
Key Concept Ranking
- Type II Secretion System
Growth of Veillonella sp. strain PK1910 (Va) in one- and two-species cultures with S. mutans (Sm) in BHI (no lactate) or BHI plus 1% lactate (+lactate). Monocultures were grown in BHI (for Sm) or BHI plus lactate (for Va) overnight anaerobically. The overnight culture was centrifuged to remove the supernatant, washed once with phosphate-buffered saline, and resuspended to an optical density at 600 nm of 1.0 in phosphate-buffered saline. The culture was inoculated into fresh medium in 1:100 dilutions either as a monoculture or in a 1:1 ratio as a mixed-species culture. The cultures were grown either in an anaerobic chamber (anaerobic) or as a static culture aerobically with 5% CO2 (aerobic) for 16 h, and the CFU determination was done by plating serially diluted cultures on BHI plus 1% lactate plus 12 μg of tetracycline/ml (Va is tetracycline resistant).
H2O2 resistance of S. mutans (Sm) and Veillonella sp. strain PK1910 (Va) in monospecies versus mixed-species cultures. S. mutans, Veillonella sp. strain PK1910, and S. gordonii (Sg) were grown in BHI to mid-exponential phase (optical density at 600 nm = 0.3), and mixed in a 1:1 ratio. H2O2 (0.02%) was added to the monospecies or mixed-species cultures for 2 h before being neutralized with catalase. Cultures were serially diluted and plated for CFU counting. Survival was calculated as the number of CFU/milliliter in the treated samples divided by CFU/milliliter of the control samples.
LC/MS profile of supernatants of monospecies and mixed-species cultures of S. mutans and Veillonella sp. strain PK1910. For the mixed-species culture, early-exponential-phase cells were mixed in a 1:1 ratio. Both monospecies and mixed-species cultures were incubated under the same conditions and harvested at late exponential phase. Supernatant from uninoculated medium (A) or medium inoculated with S. mutans (B), Veillonella sp. strain PK1910 (C), or both species (D) was concentrated by lyophilization and subjected to LC/MS analysis using a C18 reverse-phase column. No unique peak is identified in the Veillonella sp. strain PK1910 monoculture (C), as the same pattern is shown for the medium control (A). In the S. mutans monoculture (B), a peak with an apparent molecular mass of 679.53 Da was identified. This peak disappeared in the two-species culture (D), which showed a unique peak with an apparent molecular mass of 821.47 Da.
Phylogenetic tree of 16S-rRNA gene of Veillonella type strains generated using two alignment programs.
Genes related to DNA uptake, integration, and R-M in Veillonella sp. strain PK1910