Z-form extracellular DNA is a structural component of the bacterial biofilm matrix.

Biofilms are community architectures adopted by bacteria inclusive of a self-formed extracellular matrix that protects resident bacteria from diverse environmental stresses and, in many species, incorporates extracellular DNA (eDNA) and DNABII proteins for structural integrity throughout biofilm development. Here, we present evidence that this eDNA-based architecture relies on the rare Z-form. Z-form DNA accumulates as biofilms mature and, through stabilization by the DNABII proteins, confers structural integrity to the biofilm matrix. Indeed, substances known to drive B-DNA into Z-DNA promoted biofilm formation whereas those that drive Z-DNA into B-DNA disrupted extant biofilms. Importantly, we demonstrated that the universal bacterial DNABII family of proteins stabilizes both bacterial- and host-eDNA in the Z-form in situ. A model is proposed that incorporates the role of Z-DNA in biofilm pathogenesis, innate immune response, and immune evasion.

Noninflammatory 97-amino acid High Mobility Group Box 1 derived polypeptide disrupts and prevents diverse biofilms.

BACKGROUND: Bacterial biofilm communities are embedded in a protective extracellular matrix comprised of various components, with its' integrity largely owed to a 3-dimensional lattice of extracellular DNA (eDNA) interconnected by Holliday Junction (HJ)-like structures and stabilised by the ubiquitous eubacterial DNABII family of DNA-binding architectural proteins. We recently showed that the host innate immune effector High Mobility Group Box 1 (HMGB1) protein possesses extracellular anti-biofilm activity by destabilising these HJ-like structures, resulting in release of biofilm-resident bacteria into a vulnerable state. Herein, we showed that HMGB1's anti-biofilm activity was completely contained within a contiguous 97 amino acid region that retained DNA-binding activity, called 'mB Box-97'. METHODS: We engineered a synthetic version of this 97-mer and introduced a single amino acid change which lacked any post-translational modifications, and tested its activity independently and in combination with a humanised monoclonal antibody that disrupts biofilms by the distinct mechanism of DNABII protein sequestration. FINDINGS: mB Box-97 disrupted and prevented biofilms, including those formed by the ESKAPEE pathogens, and importantly reduced measurable proinflammatory activity normally associated with HMGB1 in a murine lung infection model. INTERPRETATION: Herein, we discuss the value of targeting the ubiquitous eDNA-dependent matrix of biofilms via mB Box-97 used singly or in a dual host-augmenting/pathogen-targeted cocktail to resolve bacterial biofilm infections. FUNDING: This work was supported by NIH/NIDCD R01DC011818 to L.O.B. and S.D.G. and NIH/NIAID R01AI155501 to S.D.G.

Evaluation of the caries-preventive effect of toothpaste containing surface prereacted glass-ionomer filler.

AIM: Although fluoride interventions have the most consistent benefit in preventing caries, caries still develop in high-risk individuals. Authors have evaluated the effectiveness of toothpastes containing surface prereacted glass-ionomer (S-PRG) filler in preventing tooth demineralization. METHODS: Human tooth enamel blocks were randomly assigned to six groups (30 blocks/group): no treatment (a), and toothpaste containing either 1500 ppm fluoride as sodium monofluorophosphate (NaMFP) (b), 0 wt% S-PRG (b), 1 wt% S-PRG (d), 5 wt% S-PRG (e), or 20 wt% S-PRG (f). Early caries developed on each block by 7-days demineralization using a microbial caries model. Mineral loss (Δz) and lesion depth (LD) were determined using transverse microradiography. RESULTS: Relative to the control, all toothpastes, except 0% S-PRG, significantly (analysis of variance, Tukey's, P<.0001) reduced Δz and LD at varying percentages. With regard to Δz, all comparisons were significant (P<.0001), except 0% S-PRG vs the control. Otherwise, S-PRG 1%, 5%, and 20% had 0.50, 0.37, and 0.27 times Δz compared to the control, respectively, while NaMFP had 0.61 times Δz compared to the control. LD followed an almost similar trend as Δz. CONCLUSIONS: The findings of the present study demonstrate the effectiveness of toothpaste containing S-PRG filler in inhibiting tooth demineralization in the presence of bacterial plaque, thus highlighting its potential as an effective caries-control tool for individuals at high risk of developing caries.