Biology subjects

Peters, D. I.

Publications and source records attributed to Peters, D. I..

4 recordsLinked to original sources

bioRxiv2026

Strain-Level Diversity Decouples Biofilm Architecture, Acidogenic and Aciduric Traits, and Antimicrobial Tolerance in Streptococcus mutans

Streptococcus mutans is a key contributor to dental caries, with its capacity to form structured biofilm microcolonies being a principal component of its cariogenic potential. Yet, most mechanistic studies rely on a limited number of laboratory strains and may not capture the functional diversity present across the species. Here, we characterized a panel of phenotypically and genomically diverse S. mutans isolates to determine how strain background influences biofilm architecture, extracellular matrix accumulation, acid-associated physiology, environmental responsiveness, and antimicrobial susceptibility. Quantitative high-resolution imaging revealed extensive heterogeneity in produced biofilm microcolony size, structure, and matrix composition, demonstrating that biofilm architecture is not a uniform species-level trait. Interestingly, the commonly used reference strain UA159 displayed an intermediate phenotype related to microcolony size and biofilm organization. Human saliva further altered biofilm structure and matrix accumulation in a strain-dependent manner rather than producing a standard species-wide response. Isolates also differed in growth and retained biofilm biomass under acidic conditions, while acid accumulation within mature biofilms varied independently of average microcolony volume, demonstrating that strains that produce larger microcolonies on average were not necessarily associated with greater acid accumulation. Susceptibility to the antiseptics chlorhexidine and cetylpyridinium chloride likewise differed among isolates and could not be predicted from formed biofilm architecture alone. Together, these findings demonstrate that disease-relevant traits commonly attributed to S. mutans are distributed unevenly and only partially coupled across strain backgrounds, with biofilm spatial organization failing to serve as a dominant phenotype linking acid accumulation, acid tolerance, and antimicrobial susceptibility.

microbiology↗

bioRxiv2025

Design, Development and Validation of New Fluorescent Strains for Studying Oral Streptococci

Bacterial strains that are genetically engineered to constitutively produce fluorescent proteins have aided our study of bacterial physiology, biofilm formation, and interspecies interactions. Here, we report on the construction and utilization of new strains that produce the blue fluorescent protein mTagBFP2, the green fluorescent protein sfGFP, and the red fluorescent protein mScarlet-I3 in species Streptococcus gordonii, Streptococcus mutans, and Streptococcus sanguinis. Gene fragments, developed to contain the constitutive promoter Pveg, the fluorescent gene of interest as well as aad9, providing resistance to the antibiotic spectinomycin, were inserted into selected open reading frames on the chromosome that were both transcriptionally silent and whose loss caused no measurable changes in fitness. All strains, except for sfGFP in S. sanguinis, were validated to produce a detectable and specific fluorescent signal. Individual stains, along with extracellular polymeric substances (EPS) within biofilms, were visualized and quantified through either widefield or super-resolution confocal microscopy approaches. Finally, to validate the ability to perform single cell-level analysis using the strains, we imaged and analyzed a triculture mixed-species biofilm of S. gordonii, S. mutans, and S. sanguinis grown with and without addition of human saliva. Quantification of the loss in membrane integrity using a SYTOX dye revealed that all strains had increased loss of membrane integrity with water or human saliva added to the growth media, but the proportion of the population stained by the SYTOX dye varied by species. In all, these fluorescent strains will be a valuable resource for the continued study of oral microbial ecology.

microbiology↗

bioRxiv2024

A Strain of Streptococcus mitis Inhibits Biofilm Formation of Caries Pathogens via Abundant Hydrogen Peroxide Production

Commensal oral streptococci that colonize supragingival biofilms deploy mechanisms to combat competitors within their niche. Here, we determined that Streptococcus mitis more effectively inhibited biofilm formation of Streptococcus mutans within a seven species panel. This phenotype was common amongst all assayed isolates of S. mutans, but was specific to a single strain of S. mitis, ATCC 49456. The growth inhibitory factor was not effectively carried in spent supernatants of S. mitis. However, we documented ATCC 49456 to accumulate 4-5 times more hydrogen peroxide (H2O2) than other species tested, and 5-18 times more than other S. mitis strains assayed. The S. mutans biofilm formation inhibitory phenotype was reduced when grown in media containing catalase or with a S. mitis mutant of pyruvate oxidase (spxB; pox), confirming that SpxB-dependent H2O2 production was the main antagonistic factor. Addition of S. mitis within hours after S. mutans inoculation was effective at reducing biofilm biomass, but not for 24 h pre-formed biofilms. Transcriptome analysis revealed responses for both S. mitis and S. mutans, with several S. mutans differentially expressed genes following a gene expression pattern previously described, while others being unique to the interaction with S. mitis. Finally, we show that S. mitis also affected coculture biofilm formation of several other commensal streptococci. Our study shows that strains with abundant H2O2 production are effective at inhibiting initial growth of caries pathogens like S. mutans, but are less effective at disrupting pre-formed biofilms and have the potential to influence the stability of other oral commensal strains.

microbiology↗

bioRxiv2023

Human Saliva Modifies Growth, Biofilm Architecture and Competitive Behaviors of Oral Streptococci

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.

microbiology↗