Biology subjects

Momeni, S.

Publications and source records attributed to Momeni, S..

2 recordsLinked to original sources

bioRxiv2025

Decoding the interactome for Cyclic-di-AMP-producing enzyme diadenylate cyclase (DacA)

Diadenylate cyclase (DacA) synthesizes the second messenger cyclic di-AMP (c-di-AMP), which regulates essential cellular processes across many Gram-positive and select Gram-negative bacteria/archaeal lineages. Although DacA is known to interact with regulators such as GlmM and CdaR, the breadth and functional relevance of its interactome remains poorly defined. Our study seeks to identify novel protein-protein interactions to further elucidate their unknown regulatory mechanisms and cellular roles. Using Streptococcus mutans as a model, we engineered a Flag-tagged strain (DacA-FLAG) and then performed co-immunoprecipitation under non-crosslinked and crosslinked conditions followed by mass spectrometry. We identified 22 candidates interacting proteins in non-crosslinked samples, 18 in crosslinked samples, and 6 shared between conditions. Selected partners were validated in vivo using split luciferase complementation. Notably, SMU_723 emerged as a key binding partner. AlphaFold-guided modeling predicated a direct DacA and SMU_723 interaction interface involving threonine 147, glutamine 148, and threonine 149 in DacA . Site-directed mutagenesis of these residues impaired binding, confirming their critical role. An SMU_723 deletion phenocopied a dacA deletion strain, sharing prolonged lag phase, aberrant cell morphology, reduced acid production and acid tolerance, impaired sorbitol metabolism, decreased colonization in a Drosophila model, and delayed growth upon calcium stimulation. These shared phenotypes suggest a functional and possibly regulatory link between DacA and SMU_723. Given SMU_723 sequence homology consistent with a calcium transporter, these data suggest that the DacA-723 interaction contributes to calcium homeostasis and/or calcium-responsive signaling. Collectively, our findings expand the DacA interaction network and implicate calcium transport in c-di-AMP-mediated regulation in S. mutans. ImportanceMapping the DacA interactome reveals how environmental and intracellular cues tune c-di-AMP signaling to control stress adaptation, ion balance, and virulence traits in S. mutans. By identifying new DacA-associated proteins and validating SMU_723 as a previously unrecognized interactor with genetic and phenotypic linkage to DacA, this study provides new insights into the mechanistic framework for c-di-AMP regulation in S. mutans. The connection between DacA and a putative calcium transporter highlights a plausible axis that couples second-messenger signaling to calcium homeostasis, with implications for biofilm physiology and pathogenesis. These insights open new avenues to therapeutically modulate c-di-AMP pathways.

microbiology↗

bioRxiv2023

Intraspecies interactions of Streptococcus mutans impact biofilm architecture and virulence determinants in childhood dental caries

Early childhood dental caries (ECC) is the most common chronic disease among children with a heavy disease burden among low socioeconomic populations. Streptococcus mutans is most frequently associated with initiation of ECC. Many studies report children with multiple S. mutans strains (i.e., genotypes) having greater odds of developing ECC, studies investigating intraspecies interactions in dental caries are lacking. In this study, the impact of intraspecies interactions on cariogenic and fitness traits of clinical S. mutans isolates are investigated using in-vitro and in-vivo approaches. Initially clinical S. mutans isolates of 10 children from a longitudinal epidemiological study were evaluated. S. mutans strains (G09 and G18, most prevalent) isolated from one child were used for subsequent analysis. Association analysis was used to determine if presence of multiple S. mutans genotypes within the first-year of colonization was associated with caries. Biofilm analysis was performed for single and mixed cultures to assess cariogenic traits, including biofilm biomass, intra-polysaccharide, pH, and glucan. Confocal Laser Scanning Microscopy (CLSM) and time-lapse imaging were used to evaluate spatial and temporal biofilm dynamics, respectively. A Drosophila model was used to assess colonization in-vivo. Mean biofilm pH was significantly lower in co-cultured biofilms as compared with monoculture biofilms. Doubling of S. mutans in-vitro biofilms was observed by CLSM and in-vivo colonization in Drosophila for co-cultured S. mutans. Individual strains occupied specific domains in co-culture and G09 contributed most to increased co-culture biofilm thickness and colonization in Drosophila. Biofilm formation and acid production displayed distinct signatures in time-lapsed experiments. IMPORTANCEThis study sheds light on the complex dynamics of a key contributor to early childhood dental caries (ECC) by exploring intraspecies interactions of different S. mutans strains and their impact on cariogenic traits. Utilizing clinical isolates from children with ECC, the research highlights significant differences in biofilm architecture and acid production in mixed versus single genotype cultures. The findings reveal that co-cultured S. mutans strains exhibit increased cell density and acidity, with individual strains occupying distinct domains. These insights, enhanced by use of time-lapsed Confocal Laser Scanning Microscopy and a Drosophila model, offer a deeper understanding of ECC pathogenesis and potential avenues for targeted interventions.

microbiology↗