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Choi A, Dong K, Williams E, Pia L, Batagower J, Bending P, Shin I, Peters DI, Kaspar JR. Human saliva modifies growth, biofilm architecture, and competitive behaviors of oral streptococci. mSphere 2024; 9:e0077123. [PMID: 38319113 PMCID: PMC10900908 DOI: 10.1128/msphere.00771-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 01/08/2024] [Indexed: 02/07/2024] Open
Abstract
The bacteria within supragingival biofilms participate in complex exchanges with other microbes inhabiting the same niche. One example is the mutans group streptococci (Streptococcus mutans), implicated in the development of tooth decay, and other health-associated commensal streptococci species. Previously, our group transcriptomically characterized intermicrobial interactions between S. mutans and several species of oral bacteria. However, these experiments were carried out in a medium without human saliva. To better mimic their natural environment, we first evaluated how inclusion of saliva affected growth and biofilm formation of eight Streptococcus species individually and found saliva to positively benefit growth rates while negatively influencing biofilm biomass accumulation and altering spatial arrangement. These results carried over during evaluation of 29 saliva-derived isolates of various species. Surprisingly, we also found that addition of saliva increased the competitive behaviors of S. mutans in coculture competitions against commensal streptococci that led to increases in biofilm microcolony volumes. Through transcriptomically characterizing mono- and cocultures of S. mutans and Streptococcus oralis with and without saliva, we determined that each species developed a nutritional niche under mixed-species growth, with S. mutans upregulating carbohydrate uptake and utilization pathways while S. oralis upregulated genome features related to peptide uptake and glycan foraging. S. mutans also upregulated genes involved in oxidative stress tolerance, particularly manganese uptake, which we could artificially manipulate by supplementing in manganese leading to an advantage over its opponent. Our report highlights observable changes in microbial behaviors through leveraging environmental- and host-supplied resources over their competitors. IMPORTANCE Dental caries (tooth decay) is the most prevalent disease for both children and adults nationwide. Caries are initiated from demineralization of the enamel due to organic acid production through the metabolic activity of oral bacteria growing in biofilm communities attached to the tooth's surface. Mutans group streptococci are closely associated with caries development and initiation of the cariogenic cycle, which decreases the amount of acid-sensitive, health-associated commensal bacteria while selecting for aciduric and acidogenic species that then further drives the disease process. Defining the exchanges that occur between mutans group streptococci and oral commensals in a condition that closely mimics their natural environment is of critical need toward identifying factors that can influence odontopathogen establishment, persistence, and outgrowth. The goal of our research is to develop strategies, potentially through manipulation of microbial interactions characterized here, that prevent the emergence of mutans group streptococci while keeping the protective flora intact.
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Affiliation(s)
- Allen Choi
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Kevin Dong
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Emily Williams
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Lindsey Pia
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Jordan Batagower
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Paige Bending
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Iris Shin
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Daniel I Peters
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
| | - Justin R Kaspar
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio, USA
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Choi A, Dong K, Williams E, Pia L, Batagower J, Bending P, Shin I, Peters DI, Kaspar JR. Human Saliva Modifies Growth, Biofilm Architecture and Competitive Behaviors of Oral Streptococci. bioRxiv 2023:2023.08.21.554151. [PMID: 37662325 PMCID: PMC10473590 DOI: 10.1101/2023.08.21.554151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
The bacteria within supragingival biofilms participate in complex exchanges with other microbes inhabiting the same niche. One example are the mutans group streptococci (Streptococcus mutans), implicated in the development of tooth decay, and other health-associated commensal streptococci species. Previously, our group transcriptomically characterized intermicrobial interactions between S. mutans and several species of oral bacteria. However, these experiments were carried out in a medium that was absent of human saliva. To better mimic their natural environment, we first evaluated how inclusion of saliva affected growth and biofilm formation of eight streptococci species individually, and found saliva to positively benefit growth rates while negatively influencing biomass accumulation and altering spatial arrangement. These results carried over during evaluation of 29 saliva-derived isolates of various species. Surprisingly, we also found that addition of saliva increased the competitive behaviors of S. mutans in coculture competitions against commensal streptococci that led to increases in biofilm microcolony volumes. Through transcriptomically characterizing mono- and cocultures of S. mutans and Streptococcus oralis with and without saliva, we determined that each species developed a nutritional niche under mixed-species growth, with S. mutans upregulating carbohydrate uptake and utilization pathways while S. oralis upregulated genome features related to peptide uptake and glycan foraging. S. mutans also upregulated genes involved in oxidative stress tolerance, particularly manganese uptake, which we could artificially manipulate by supplementing in manganese to give it an advantage over its opponent. Our report highlights observable changes in microbial behaviors via leveraging environmental- and host-supplied resources over their competitors.
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Affiliation(s)
- Allen Choi
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Kevin Dong
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Emily Williams
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Lindsey Pia
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Jordan Batagower
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Paige Bending
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Iris Shin
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Daniel I Peters
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
| | - Justin R Kaspar
- Division of Biosciences, The Ohio State University College of Dentistry, Columbus, Ohio
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Lee K, Kaspar JR, Rojas-Carreño G, Walker AR, Burne RA. A single system detects and protects the beneficial oral bacterium Streptococcus sp. A12 from a spectrum of antimicrobial peptides. Mol Microbiol 2021; 116:211-230. [PMID: 33590560 DOI: 10.1111/mmi.14703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 02/11/2021] [Accepted: 02/11/2021] [Indexed: 10/22/2022]
Abstract
The commensal bacterium Streptococcus sp. A12 has multiple properties that may promote the stability of health-associated oral biofilms, including overt antagonism of the dental caries pathogen Streptococcus mutans. A LanFEG-type ABC transporter, PcfFEG, confers tolerance to the lantibiotic nisin and enhances the ability of A12 to compete against S. mutans. Here, we investigated the regulation of pcfFEG and adjacent genes for a two-component system, pcfRK, to better understand antimicrobial peptide resistance by A12. Induction of pcfFEG-pcfRK was the primary mechanism to respond rapidly to nisin. In addition to nisin, PcfFEG conferred tolerance by A12 to a spectrum of lantibiotic and non-lantibiotic antimicrobial peptides produced by a diverse collection of S. mutans isolates. Loss of PcfFEG resulted in the altered spatio-temporal arrangement of A12 and S. mutans in a dual-species biofilm model. Deletion of PcfFEG or PcfK resulted in constitutive activation of pcfFEG and expression of pcfFEG was inhibited by small peptides in the pcfK mutant. Transcriptional profiling of pcfR or pcfK mutants combined with functional genomics revealed peculiarities in PcfK function and a novel panel of genes responsive to nisin. Collectively, the results provide fundamental insights that strengthen the foundation for the design of microbial-based therapeutics to control oral infectious diseases.
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Affiliation(s)
- Kyulim Lee
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Justin R Kaspar
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA.,Division of Biosciences, College of Dentistry, Ohio State University, Columbus, OH, USA
| | - Gisela Rojas-Carreño
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Alejandro R Walker
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Robert A Burne
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
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Kaspar JR, Lee K, Richard B, Walker AR, Burne RA. Direct interactions with commensal streptococci modify intercellular communication behaviors of Streptococcus mutans. ISME J 2021; 15:473-488. [PMID: 32999420 PMCID: PMC8027600 DOI: 10.1038/s41396-020-00789-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 09/10/2020] [Accepted: 09/18/2020] [Indexed: 02/07/2023]
Abstract
The formation of dental caries is a complex process that ultimately leads to damage of the tooth enamel from acids produced by microbes in attached biofilms. The bacterial interactions occurring within these biofilms between cariogenic bacteria, such as the mutans streptococci, and health-associated commensal streptococci, are thought to be critical determinants of health and disease. To better understand these interactions, a Streptococcus mutans reporter strain that actively monitors cell-cell communication via peptide signaling was cocultured with different commensal streptococci. Signaling by S. mutans, normally highly active in monoculture, was completely inhibited by several species of commensals, but only when the bacteria were in direct contact with S. mutans. We identified a novel gene expression pattern that occurred in S. mutans when cultured directly with these commensals. Finally, mutant derivatives of commensals lacking previously shown antagonistic gene products displayed wild-type levels of signal inhibition in cocultures. Collectively, these results reveal a novel pathway(s) in multiple health-associated commensal streptococci that blocks peptide signaling and induces a common contact-dependent pattern of differential gene expression in S. mutans. Understanding the molecular basis for this inhibition will assist in the rational design of new risk assessments, diagnostics, and treatments for the most pervasive oral infectious diseases.
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Affiliation(s)
- Justin R Kaspar
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA.
- Division of Biosciences, College of Dentistry, Ohio State University, Columbus, OH, USA.
| | - Kyulim Lee
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Brook Richard
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Alejandro R Walker
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Robert A Burne
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
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Ishkov IP, Kaspar JR, Hagen SJ. Spatial Correlations and Distribution of Competence Gene Expression in Biofilms of Streptococcus mutans. Front Microbiol 2021; 11:627992. [PMID: 33510740 PMCID: PMC7835332 DOI: 10.3389/fmicb.2020.627992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 12/17/2020] [Indexed: 11/13/2022] Open
Abstract
Streptococcus mutans is an important pathogen in the human oral biofilm. It expresses virulent behaviors that are linked to its genetic competence regulon, which is controlled by comX. Expression of comX is modulated by two diffusible signaling peptides, denoted CSP and XIP, and by other environmental cues such as pH and oxidative stress. The sensitivity of S. mutans competence to environmental inputs that may vary on microscopic length scales raises the question of whether the biofilm environment creates microniches where competence and related phenotypes are concentrated, leading to spatial clustering of S. mutans virulence behaviors. We have used two-photon microscopy to characterize the spatial distribution of comX expression among individual S. mutans cells in biofilms. By analyzing correlations in comX activity, we test for spatial clustering that may suggest localized competence microenvironments. Our data indicate that both competence-signaling peptides diffuse efficiently through the biofilm. XIP elicits a population-wide response. CSP triggers a Poisson-like, spatially random comX response from a subpopulation of cells that is homogeneously dispersed. Our data indicate that competence microenvironments if they exist are small enough that the phenotypes of individual cells are not clustered or correlated to any greater extent than occurs in planktonic cultures.
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Affiliation(s)
- Ivan P Ishkov
- Department of Physics, University of Florida, Gainesville, FL, United States
| | - Justin R Kaspar
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, United States
| | - Stephen J Hagen
- Department of Physics, University of Florida, Gainesville, FL, United States
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Abstract
Streptococci, including the dental pathogen Streptococcus mutans, undergo cell-to-cell signaling that is mediated by small peptides to control critical physiological functions such as adaptation to the environment, control of subpopulation behaviors and regulation of virulence factors. One such model pathway is the regulation of genetic competence, controlled by the ComRS signaling system and the peptide XIP. However, recent research in the characterization of this pathway has uncovered novel operons and peptides that are intertwined into its regulation. These discoveries, such as cell lysis playing a critical role in XIP release and importance of bacterial self-sensing during the signaling process, have caused us to reevaluate previous paradigms and shift our views on the true purpose of these signaling systems. The finding of new peptides such as the ComRS inhibitor XrpA and the peptides of the RcrRPQ operon also suggests there may be more peptides hidden in the genomes of streptococci that could play critical roles in the physiology of these organisms. In this review, we summarize the recent findings in S. mutans regarding the integration of other circuits into the ComRS signaling pathway, the true mode of XIP export, and how the RcrRPQ operon controls competence activation. We also look at how new technologies can be used to re-annotate the genome to find new open reading frames that encode peptide signals. Together, this summary of research will allow us to reconsider how we perceive these systems to behave and lead us to expand our vocabulary of peptide signals within the genus Streptococcus.
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Affiliation(s)
- Justin R. Kaspar
- Department of Oral Biology, University of Florida, Gainesville, FL, United States
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