Porphyromonas gingivalis is highly sensitive to inhibitors of a proton-pumping ATPase

Proton Pumping ATPases: Rotational Catalysis, Physiological Roles in Oral Pathogenic Bacteria, and Inhibitors

Proton pumping ATPases, both F-type and V/A-type ATPases, generate ATP using electrochemical energy or pump protons/sodium ions by hydrolyzing ATP. The enzymatic reaction and proton transport are coupled through subunit rotation, and this unique rotational mechanism (rotational catalysis) has been intensively studied. Single-molecule and thermodynamic analyses have revealed the detailed rotational mechanism, including the catalytically inhibited state and the roles of subunit interactions. In mammals, F- and V-ATPases are involved in ATP synthesis and organelle acidification, respectively. Most bacteria, including anaerobes, have F- and/or A-ATPases in the inner membrane. However, these ATPases are not believed to be essential in anaerobic bacteria since anaerobes generate sufficient ATP without oxidative phosphorylation. Recent studies suggest that F- and A-ATPases perform indispensable functions beyond ATP synthesis in oral pathogenic anaerobes; F-ATPase is involved in acid tolerance in Streptococcus mutans, and A-ATPase mediates nutrient import in Porphyromonas gingivalis. Consistently, inhibitors of oral bacterial F- and A-ATPases, such as phytopolyphenols and bedaquiline, strongly diminish growth and survival. Herein, we discuss rotational catalysis of bacterial F- and A-ATPases, and discuss their physiological roles, focusing on oral bacteria. We also review the effects of ATPase inhibitors on the growth and survival of oral pathogenic bacteria. The features of the catalytic mechanism and unique physiological roles in oral bacteria highlight the potential for proton pumping ATPases to serve as targets for oral antimicrobial agents.

Helicobacter pylori, periodontal pathogens, and their interactive association with incident all-cause and Alzheimer's disease dementia in a large national survey

Co-infection between Helicobacter pylori (Hp) and groups of periodontal pathogens may alter the onset of Alzheimer's disease (AD) and all-cause dementia. We examined the interactive associations among Hp sero-positivity, periodontal disease (Pd), and infections with incident AD and all-cause dementia, among older adults (≥65 years at baseline). Up to 1431 participants from phase 1 of the National Health and Nutrition Survey III (1988-1991) had complete data till January 1st, 2014 on Hp sero-positivity with a mean follow-up of 10-11 years for AD and all-cause dementia incidence. Exposures consisted of 19 periodontal pathogens, constructed factors and clusters, and two Pd markers- probing depth and clinical attachment loss (CAL). Cox proportional hazards models were performed. Around 55% of the selected sample was Hp⁺. We found that Prevotella intermedia, Campylobacter Rectus, Factor 2 (Pi/Prevotella nigrescens/Prevotella melaninogenica), and the Orange-Red cluster interacted synergistically with Hp sero-positivity, particularly with respect to AD incidence. The presence of higher levels of Actinomyces Naeslundii (An) enhanced the effect of being Hp⁺ on both AD and all-cause dementia incidence. In contrast, Fusobacterim nucleatum (Fn), and Factor 1 (which included Fn), exhibited an antagonistic interaction with Hp in relation to all-cause dementia. Both probing depth and CAL had direct associations with all-cause dementia among Hp⁺ individuals, despite nonsignificant interaction. Selected periodontal pathogen titers, factors, and clusters interacted mostly synergistically, with Hp sero-positivity, to alter the risk of AD and all-cause dementia. Ultimately, a randomized controlled trial is needed, examining effects of co-eradication of Hp and select periodontal pathogens on neurodegenerative disease.

In-situ sludge reduction performance and mechanism in an anoxic/aerobic process coupled with alternating aerobic/anaerobic side-stream reactor

Activated sludge process with anaerobic side-stream reactors (SR) in the sludge recirculation can achieve in-situ sludge reduction, but sludge reduction efficiency is limited with the low hydraulic retention time (HRT) of SR. An anoxic/aerobic (AO) process, AO coupled with anaerobic SR and AO coupled with alternating aerobic/anaerobic side-stream reactor (AO-OASR) were operated to investigate enhancing effects of alternative aerobic and anaerobic condition (AltOA) in SR on sludge reduction and pollutants removal performance. The AltOA was firstly proposed into SR with a low HRT during the long-term continuous operation. The results showed that AO-OASR presented a lower effluent COD concentration (29.6%) with no adverse effect on nitrogen removal, compared to AO, owing to the intensified refractory carbon reuse in the mainstream aerobic tank. The sludge yield in AO-OASR (0.240 g SS/g COD) was 39.7% lower than that in AO. The OASR accelerated sludge lysis and particle organic matter hydrolysis due to the weakened network strength of flocs, leading to an enhanced increase (17.3 mg/L) of dissolved organic matter (DOM), especially for the fraction of molecular weight (MW) < 25 kDa. The OASR reduced the adenosine triphosphate (ATP) content for heterotrophic anabolism in the mainstream reactor by 42.9%, compared to the ASR. MW < 25 kDa of DOM caused the disturbance of oxidative phosphorylation with a decreasing ATP synthase activity under high-level electronic transport system, leading to ATP dissipation. The cooperation interaction of predator (norank_Chitinophagales), hydrolytic/fermentative bacteria (unclassified_Bacteroidia and Delftia), and slow grower (Trichococcus) played a key role in improving the sludge reduction and carbon reuse in AO-OASR. The results provided an efficient and cost-saving technology for sludge reduction with modified SR under low HRT, which is meaningful to overcome the present bottleneck of deficient reduction efficiency for application in wastewater treatment plants.

Curcumin: A review of experimental studies and mechanisms related to periodontitis treatment

Curcumin is the main active ingredient of turmeric, which has a wide range of pharmacological effects, including antitumor, antibacterial, anti-inflammatory, anti-oxidation, immune regulation, and so on. Periodontitis is a prevalent oral inflammatory disease caused by a variety of factors. In recent years, many studies have shown that curcumin has a potential role on the treatment of periodontitis. Curcumin has been used in research related to the treatment of periodontitis in the form of solution, chip, gel, and capsule. Combined with other periodontitis treatment methods, such as scaling and root planing (SRP) and photodynamic therapy (PDT), can enhance curcumin's efficacy in treating periodontitis. In addition to natural curcumin, chemically modified curcumin, such as 4-phenylaminocarbonyl bis-demethoxy curcumin (CMC 2.24) and 4-methoxycarbonyl curcumin (CMC 2.5), have also been used in animal models of periodontitis. Here, this paper reviews the research progress of curcumin on the treatment of periodontitis and its related mechanisms.

Fragment-based discovery of the first nonpeptidyl inhibitor of an S46 family peptidase

Antimicrobial resistance is a global public threat and raises the need for development of new antibiotics with a novel mode of action. The dipeptidyl peptidase 11 from Porphyromonas gingivalis (PgDPP11) belongs to a new class of serine peptidases, family S46. Because S46 peptidases are not found in mammals, these enzymes are attractive targets for novel antibiotics. However, potent and selective inhibitors of these peptidases have not been developed to date. In this study, a high-resolution crystal structure analysis of PgDPP11 using a space-grown crystal enabled us to identify the binding of citrate ion, which could be regarded as a lead fragment mimicking the binding of a substrate peptide with acidic amino acids, in the S1 subsite. The citrate-based pharmacophore was utilized for in silico inhibitor screening. The screening resulted in an active compound SH-5, the first nonpeptidyl inhibitor of S46 peptidases. SH-5 and a lipophilic analog of SH-5 showed a dose-dependent inhibitory effect against the growth of P. gingivalis. The binding mode of SH-5 was confirmed by crystal structure analysis. Thus, these compounds could be lead structures for the development of selective inhibitors of PgDPP11.