Proton Motive Force Research Articles

Gen-AI Methods, Molecular Docking and Molecular Dynamics Simulations for Identification of Novel Inhibitors of MmPL3 Transporter of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), the bacterium responsible for tuberculosis (TB), employs mycolic acids to build its cell wall. This robust structure plays a vital role in protecting the bacterium from external threats and contributes to its resistance against antibiotics. Mycobacterial membrane protein Large 3 (MmpL3), a secondary resistance nodulation division transporter, is essential in mycolic acid biosynthesis, transporting mycolic acid precursors into the periplasm using the proton motive force. Due to its role in bacterial cell wall formation, it is a promising target for new tuberculosis treatments. In this study, starting with 85 known MmPL3 compounds, the artificial intelligence (AI)-assisted tool “Design of Druglike Analogues (DeLA-Drug)” was employed to generate about 15,000 novel molecules. These compounds were then subjected to structure-based high-throughput virtual screening and molecular dynamics (MD) simulations to identify potential novel inhibitors of MmpL3. The binding affinity was obtained by docking the above molecules at the SQ109 binding site in MmPL3, followed by pharmacokinetics and toxicity, which were used to reduce the chemical space. Finally, five ligands were subjected to 100 ns MD simulations to investigate the binding energetics of inhibitors to MmpL3. These compounds demonstrated stable binding and favorable drug-like properties, indicating that they could serve as potential novel inhibitors of MmpL3 for Mtb.

Bioenergetic suppression by redox-active metabolites promotes antibiotic tolerance in Pseudomonas aeruginosa

The proton-motive force (PMF), consisting of a pH gradient and a membrane potential (ΔΨ) underpins many processes essential to bacterial growth and/or survival. Yet bacteria often enter a bioenergetically diminished state characterized by a low PMF. Consequently, they have increased tolerance for diverse stressors, including clinical antibiotics. Despite the ubiquity of low metabolic rates in the environment, the extent to which bacteria have agency over entry into such a low-bioenergetic state has received relatively little attention. Here, we tested the hypothesis that production of redox-active metabolites (RAMs) could drive such a physiological transition. Pseudomonas aeruginosa is an opportunistic pathogen that produces phenazines, model RAMs that are highly toxic in the presence of molecular oxygen (O2). Under oxic conditions, the phenazines pyocyanin and phenazine-1-carboximide, as well as toxoflavin-a RAM produced by Burkholderia species-suppress the ΔΨ in distinct ways across distributions of single cells, reduce the efficiency of proton pumping, and lower cellular adenosine-triphosphate (ATP) levels. In planktonic culture, the degree and rate by which each RAM lowers the ΔΨ correlates with the protection it confers against antibiotics that strongly impact cellular energy flux. This bioenergetic suppression requires the RAM's presence and corresponds to its cellular reduction rate and abiotic oxidation rate by O2; it can be reversed by increasing the ΔΨ with nigericin. RAMs similarly impact the bioenergetic state of cells in (hyp)oxic biofilm aggregates. Collectively, these findings demonstrate that bacteria can suppress their bioenergetic state by the production of endogenous toxins in a manner that bolsters stress resilience.

SQ31f is a potent non-tuberculous mycobacteria antibiotic by specifically targeting the mycobacterial F-ATP synthase.

Non-tuberculous mycobacteria (NTM) infection presents a growing global health problem and requires new antibiotics targeting enzymes that are essential for the pathogens under various metabolic conditions, with high target specificity, good solubility and with attractive combinatory potency. SQ31f was synthesized by a simplified synthesis protocol, and its effect on growth inhibition of fast- and slow-growing NTM and clinical isolates, whole-cell ATP depletion, ex vivo macrophages and its potency in combination with other antibiotics were evaluated. Molecular docking studies were employed to assess SQ31f's binding mode. We present- squaramide SQ31f as a novel anti-NTM inhibitor targeting the NTM F1FO-ATP synthase, essential for ATP formation, regulation of ATP homeostasis and proton motive force under multiple growth conditions. The potency of SQ31f in growth inhibition of fast- and slow-growing NTM and clinical isolates correlates with whole-cell ATP depletion, which is not caused by altered oxygen consumption. SQ31f's high aqueous solubility enables binding to the waterfilled cytosolic proton half channel in the subunits a-c interface of the FO domain. As presented for the fast-growing Mycobacterium abscessus, the compound is active against intracellular-residing M. abscessus. Importantly, SQ31f shows an additive effect of the anti-M. abscessus drugs clofazimine, rifabutin or amikacin, and an attractive potentiation of linezolid, clarithromycin, or the oral pair tebipenem and avibactam. SQ31f represents an attractive inhibitor to tackle the issues associated with NTM drug tolerance and toxicity. Its combinatory potency with anti-M. abscessus drugs holds potential for overcoming resistance, while also reducing intensive compound synthesis and associated costs.

The interplay between LHCSR and PSBS proteins provides photoprotection in Chlamydomonas reinhardtii pgr5 mutant under high light

Cyclic electron transport (CET) is a vital alternative route that protects against photodamage and aids in energy production. This process depends on proton gradient regulation 5 (PGR5) and PGRL1-dependent pathways associated with CET. The exact roles of these proteins in photosystem I photochemistry under prolonged high light conditions are not fully understood. Continuous light adaptation hinges on two critical mechanisms: alterations in the proton motive force (pmf) and adjustments in the ratio of proteins activated by high light that dissipate excess light through non-photochemical quenching (NPQ). To explore this, we studied pgrl1 and pgr5 mutants to gauge their roles in balancing photochemistry and photoacclimation. These mutants showed inhibited growth, reduced photosynthetic efficiency, and a lowered pmf, leading to diminished non-photochemical energy quenching (qE) under high light. Prolonged high light exposure slowed down unregulated energy losses Y(NO), and relaxation helped regulate photosynthetic activity by increasing photoinhibitory quenching (qI), thus preventing further damage to the photosystem. The precise balance between the two pmf components, ΔpH and Δψ, is critical for controlling photochemistry and photoacclimation, yet remains elusive. In pgr5 reduced pmf led to an accumulation of cytochrome b6f under high light, and a decrease in the ΔpH component increased the Δψ component's role in photosynthetic acclimation. Notably, light-harvesting complex stress response protein 3 (LHCSR3) showed decreased expression in pgrl1, whereas pgr5 exhibited no expression of both LHCSR3 and LHCSR1 under high light conditions. Moreover, continuous increase in PSBS protein accumulation in pgr5 suggests enhanced photoprotection in the absence of LHCSR3 under high light. The study provides significant insights into how cyclic electron transport (CET) regulates photoprotective proteins LHCSR and PSBS, influencing Chlamydomonas' survival strategies.

Proton motive force and antibiotic tolerance in bacteria.

Bacterial antibiotic tolerance is a decades-old phenomenon in which a bacterial sub-population, commonly known as persisters, does not respond to antibiotics and remains viable upon prolonged antimicrobial treatment. Persisters are detectable in populations of bacterial strains that are not antibiotic-resistant and are known to be responsible for treatment failure and the occurrence of chronic and recurrent infection. The clinical significance of antibiotic tolerance is increasingly being recognized and comparable to antibiotic resistance. To eradicate persisters, it is necessary to understand the cellular mechanisms underlying tolerance development. Previous works showed that bacterial antibiotic tolerance was attributed to the reduction in metabolic activities and activation of the stringent response, SOS response and the toxin-antitoxin system which down-regulates transcription functions. The latest research findings, however, showed that decreased metabolic activities alone do not confer a long-lasting tolerance phenotype in persisters, and that active defence mechanisms such as efflux and DNA repair are required for the long-term maintenance of phenotypic tolerance. As such active tolerance-maintenance mechanisms are energy-demanding, persisters need to generate and maintain the transmembrane proton motive force (PMF) for oxidative phosphorylation. This minireview summarizes the current understanding of cellular mechanisms essential for prolonged expression of phenotypic antibiotic tolerance in bacteria, with an emphasis on the importance of generation and maintenance of PMF in enabling proper functioning of the active tolerance mechanisms in persisters. How such mechanisms can be utilized as targets for the development of anti-persister strategies will be discussed.

Zn(II) enhances the antimicrobial effect of chloroxine and structural analogues against drug-resistant ESKAPE pathogens in vitro

The emerging antibiotic-resistant bacteria, especially the “ESKAPE” pathogens, pose a continuous threat to global health. In this study, we explored metalloantibiotics as promising therapeutics and innovative antimicrobial agents. The role of metal in the antimicrobial activity of chloroxine (5,7-dichloro-8-hydroxyquinoline), as a metalloantibiotic, was investigated by minimal inhibit concentration (MIC) assay and a series of assays, including growth curve, time-killing, and UV–visible spectroscopy and PAR (4-(2-pyridylazo)-resorcinol) competition assays. Both chloroxine and its structural analogues exhibited increased antibacterial potency against Gram-positive bacteria compared to Gram-negative bacteria. The introduction of exogenous manganese or zinc ions significantly boosted chloroxine’s antibacterial efficacy against Gram-negative bacteria, including the notorious ESKAPE pathogens. However, the enhanced antibacterial activity induced by zinc ions could be negated in the presence of copper or ferrous iron ions, as well as changes in oxygen availability, highlighting the involvement of proton motive force, oxidative and antioxidative systems. Notably, chloroxine effectively inhibited the enzymatic activity of superoxide dismutase (SOD). In addition, chloroxine could reverse polymyxin and carbapenem resistance in E. coli in vitro. Therefore, these results suggested that chloroxine with zinc ions are promising therapeutics and antibiotics potentiator to combat multidrug-resistant ESKAPE pathogens

Guanethidine Enhances the Antibacterial Activity of Rifampicin Against Multidrug-Resistant Bacteria

The escalating global threat of antibiotic resistance necessitates innovative strategies, such as the combination of antibiotics with adjuvants. Monotherapy with rifampicin is more likely to induce resistance in pathogens compared to other antibiotics. Herein, we found that the antihypertensive drug guanethidine enhanced the activity of rifampicin against certain clinically resistant Gram-negative bacteria, resulting in a reduction of up to 128-fold in the minimum inhibitory concentration. In infected animal models, this combination has achieved treatment benefits, including increased survival and decreased bacterial burden. The antimicrobial mechanism of guanethidine in synergy with rifampicin involves the disruption of the outer membrane of Gram-negative bacteria, leading to dissipation of the proton motive force. This results in an increase in reactive oxygen species and a reduction in ATP synthesis, severely disturbing energy metabolism and ultimately increasing bacterial mortality. In summary, guanethidine has the potential to become a novel adjuvant for rifampicin, offering a new option for the treatment of clinical Gram-negative bacterial infections.

Dynamic interplay between a TonB-dependent heme transporter and a TonB protein in a membrane environment.

Gram-negative bacteria import scarce nutrients such as metals and vitamins by an energized mechanism involving a multicomponent protein system that spans the cell envelope. It consists of an outer membrane TonB-dependent transporter (TBDT) and a TonB complex in the inner membrane that provides the proton motive force energy for the nutrient entry. Despite the intense research efforts focused on this system (a) from structural and fundamental microbiology perspectives and (b) for the interest in the development of new antibacterial strategies, the molecular mechanism of the system is not at all well understood. The lack of understanding comes from incomplete structural data and the experimental difficulties of studying an inherently flexible multicomponent complex that resides within the heterogeneous environment of the double membrane bacterial cell envelope. To address these challenges and obtain a comprehensive view of the molecular interactions at atomic level, here, we have used the combined power of advanced molecular simulations and complementary microbiology and biochemical experiments. Our results represent a significant step forward in understanding the structural and molecular bases of this vital mechanism.

Response of growth and chlorophyll fluorescence parameters of mulberry seedlings to waterlogging stress

This study aimed to investigate the adaptive mechanisms of mulberry (Morus alba) to waterlogged conditions, with a specific focus on the development of adventitious roots (ARs), alteration of growth strategies, and adjustment of chlorophyll fluorescence parameters. To achieve this goal, 4-year-old potted mulberry plants were selected for research, and a waterlogging simulation method was implemented. Four treatments were established to investigate the effects of varying water conditions on leaf waterlogging damage, the number of ARs, plant height, chlorophyll fluorescence parameters, and proton motive force (pmf) parameters in mulberry plants. These treatments included the control group (CK), shallow submerged group (SS), half-submerged group (HS) and deep submerged group (DS). Our results showed that (1) The number of ARs in each group increased with increasing waterlogging time. (2) Waterlogging stress inhibited the height growth of mulberry, and the changes in plant height in the HS and DS groups were significantly lower than those in the CK and SS groups. (3) The maximum photochemical quantum yield (Fv/Fm) in the HS and DS groups decreased significantly under waterlogging stress. The nonphotochemical quenching (NPQt) of mulberry leaves in the submergence group increased significantly in the early stage of waterlogging stress, and the NPQt in the submergence group increased continuously with increasing waterlogging time. (4) Thylakoid conductivity to protons (gH+) in the leaves of mulberry decreased significantly under waterlogging stress, whereas the steady-state rate of proton flux (vH+) and total electrochromic shift (ECSt) increased significantly. The morphological, physiological, and ecological responses of mulberry plants to waterlogging stress include the timely generation of ARs at the stem base, the adjustment of plant growth strategies, and the repair of photosynthetic response centers in leaves through heat dissipation and thylakoid acidification mechanisms.

Colistin-niclosamide-loaded nanoemulsions and nanoemulsion gels for effective therapy of colistin-resistant Salmonella infections.

Colistin (COL) is regarded as a last-resort treatment for infections by multidrug-resistant (MDR) Gram-negative bacteria. The emergence of colistin-resistant Enterobacterales poses a significant global public health concern. Our study discovered that niclosamide (NIC) reverses COL resistance in Salmonella via a checkerboard assay. However, poor solubility and bioavailability of NIC pose challenges. In this study, we prepared a self-nanoemulsifying drug delivery system (SNEDDS) co-encapsulating NIC and COL. We characterized the physicochemical properties of the resulting colistin-niclosamide-loaded nanoemulsions (COL/NIC-NEs) and colistin-niclosamide-loaded nanoemulsion gels (COL/NIC-NEGs), assessing their antibacterial efficacy in vitro and in vivo. The COL/NIC-NEs exhibited a droplet size of 19.86 nm with a zeta potential of -1.25 mV. COL/NIC-NEs have excellent stability, significantly enhancing the solubility of NIC while also demonstrating a pronounced sustained-release effect. Antimicrobial assays revealed that the MIC of COL in COL/NIC-NEs was reduced by 16-128 times compared to free COL. Killing kinetics and scanning electron microscopy confirmed enhanced antibacterial activity. Antibacterial mechanism studies reveal that the COL/NIC-NEs and COL/NIC-NEGs could enhance the bactericidal activity by damaging cell membranes, disrupting proton motive force (PMF), inhibiting multidrug efflux pump, and promoting oxidative damage. The therapeutic efficacy of the COL/NIC-NEs and COL/NIC-NEGs is further demonstrated in mouse intraperitoneal infection models with COL-resistant Salmonella. To sum up, COL/NIC-NEs and COL/NIC-NEGs are a potentially effective strategies promising against COL-resistant Salmonella infections.

Reductive dehalogenase of Dehalococcoides mccartyi strain CBDB1 reduces cobalt- containing metal complexes enabling anodic respiration.

Microorganisms capable of direct or mediated extracellular electron transfer (EET) have garnered significant attention for their various biotechnological applications, such as bioremediation, metal recovery, wastewater treatment, energy generation in microbial fuel cells, and microbial or enzymatic electrosynthesis. One microorganism of particular interest is the organohalide-respiring bacterium Dehalococcoides mccartyi strain CBDB1, known for its ability to reductively dehalogenate toxic and persistent halogenated organic compounds through organohalide respiration (OHR), using halogenated organics as terminal electron acceptors. A membrane-bound OHR protein complex couples electron transfer to proton translocation across the membrane, generating a proton motive force, which enables metabolism and proliferation. In this study we show that the halogenated compounds can be replaced with redox mediators that can putatively shuttle electrons between the OHR complex and the anode, coupling D. mccartyi cells to an electrode via mediated EET. We identified cobalt-containing metal complexes, referred to as cobalt chelates, as promising mediators using a photometric high throughput methyl viologen-based enzyme activity assay. Through various biochemical approaches, we show that cobalt chelates are specifically reduced by CBDB1 cells, putatively by the reductive dehalogenase subunit (RdhA) of the OHR complex. Using cyclic voltammetry, we also demonstrate that cobalt chelates exchange electrons with a gold electrode, making them promising candidates for bioelectrochemical cultivation. Furthermore, using the AlphaFold 2-calculated RdhA structure and molecular docking, we found that one of the identified cobalt chelates exhibits favorable binding to RdhA, with a binding energy of approximately -28 kJ mol-1. Taken together, our results indicate that bioelectrochemical cultivation of D. mccartyi with cobalt chelates as anode mediators, instead of toxic halogenated compounds, is feasible, which opens new perspectives for bioremediation and other biotechnological applications of strain CBDB1.

Activity of the Caged Xanthone Morellic Acid against Vancomycin-Resistant Enterococcus Infection by Targeting the Bacterial Membrane.

Vancomycin-resistant Enterococcus (VRE) is an important nosocomial opportunistic pathogen that is associated with multidrug resistance. Here, we demonstrate that morellic acid inhibits VRE by restoring its sensitivity to vancomycin and ampicillin with low drug resistance and efficient biofilm clearance effects. Morellic acid binds to inner membrane phospholipids, such as phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL) of VRE, such that the fluidity and proton-motive force (PMF) interfere with the damaged inner membrane, causing intracellular reactive oxygen species (ROS) accumulation and bacterial death. Transcriptional analyses supported this effect on inner membrane-related pathways such as fatty acid biosynthesis and glycerophospholipid metabolism. Moreover, morellic acid significantly eliminated residual bacteria in the spleen, liver, kidneys, and abdominal effusion in mice. Our findings indicate the potential applications of morellic acid as an antibacterial agent or adjuvant for treating VRE infections.

Involvement of plasma membrane H+-ATPase in the nitrate-nutrition uptake and utilization in indica rice

Utilization of nitrogen by crops is essential for sustainable agriculture. The transport of nitrate (NO3−) across the plasma membrane is a critical gateway for N uptake and subsequent utilization. This process requires proton (H+) coupled cotransport, which is driven by proton motive force, provided by plasma membrane (PM) H+-ATPase. In this report, two indica rice varieties [Meixiangzhan 2 (MXZ) and Jifengyou 1002 (JFY)] in South China were selected and cultivated in hydroponic solution with 0.5 mM or 2.0 mM NO3− as the N source. The JFY exhibited stronger growth with higher biomass than MXZ under both 0.5 mM and 2.0 mM NO3−. PM H+-ATPase activity of JFY roots was significantly higher than that of MXZ. The higher PM H+-ATPase activity in JFY was consistent with a higher abundance of PM H+-ATPase protein and higher transcription levels of OSAs, such as OSA2, OSA7 and OSA8 in roots, OSA3, OSA7 and OSA8 in leaves. The expression of nitrate transporters (OsNRT1;1b, OsNRT2.1, OsNRT2.2, and OsNAR2.1) were also higher in roots or shoots of JFY than those in MXZ. Under 0.5 mM and 2.0 mM NO3−, the NO3− absorption and translocation rate, nitrate content, as well as nitrate reductase (NR) activity were all significantly higher in JFY, as compared to those in MXZ. Taken together, in JFY and MXZ, a higher level of PM H+-ATPase protein and higher activity coupled with greater efficiency in nitrate uptake, translocation and assimilation, suggesting the existence of a close correlation between PM H+-ATPase and nitrate utilization in indica rice. PM H+-ATPase may one of the elite genes that can contribute to nitrate use efficiency in rice.

Arabidopsis HAK5 under low K+ availability operates as PMF powered high-affinity K+ transporter

Plants can survive in soils of low micromolar potassium (K+) concentrations. Root K+ intake is accomplished by the K+ channel AKT1 and KUP/HAK/KT type high-affinity K+ transporters. Arabidopsis HAK5 mutants impaired in low K+ acquisition have been identified already more than two decades ago, the molecular mechanism, however, is still a matter of debate also because of lack of direct measurements of HAK5-mediated K+ currents. When we expressed AtHAK5 in Xenopus oocytes together with CBL1/CIPK23, no inward currents were elicited in sufficient K+ media. Under low K+ and inward-directed proton motive force (PMF), the inward K+ current increased indicating that HAK5 energetically couples the uphill transport of K+ to the downhill flux of H+. At extracellular K+ concentrations above 25 μM, the initial rise in current was followed by a concentration-graded inactivation. When we replaced Tyr450 in AtHAK5 to Ala the K+ affinity strongly decreased, indicating that AtHAK5 position Y450 holds a key for K+ sensing and transport. When the soil K+ concentration drops toward the range that thermodynamically cannot be covered by AKT1, the AtHAK5 K+/H+ symporter progressively takes over K+ nutrition. Therefore, optimizing K+ use efficiency of crops, HAK5 could be key for low K+ tolerant agriculture.

Acetylshikonin reduces the spread of antibiotic resistance via plasmid conjugation

The plasmid-mediated conjugative transfer of antibiotic resistance genes (ARGs) stands out as the primary driver behind the dissemination of antimicrobial resistance (AMR). Developing effective inhibitors that target conjugative transfer represents an efficient strategy for addressing the issue of AMR. Here, we studied the effect of acetylshikonin (ASK), a botanical derivative, on plasmid conjugation. The conjugative transfer of RP4-7 plasmid inter and intra species was notably reduced by ASK. The conjugation process of IncI2 and IncX4 plasmids harboring the mobile colistin resistance gene (mcr-1), IncX4 and IncX3 plasmids containing the carbapenem resistance gene (blaNDM-5), and IncFI and IncFII plasmids possessing the tetracycline resistance gene [tet(X4)] were also reduced by ASK. Importantly, the conjugative transfer frequency of mcr-1 positive IncI2 plasmid in mouse peritoneal conjugation model and gut conjugation model was reduced by ASK. The mechanism investigation showed that ASK disrupt the functionality of the bacterial cell membrane. Furthermore, the proton motive force (PMF) was dissipated. In addition, ASK blocked the electron transmission in bacteria's electron transport chain (ETC) through disturbing the quinone interaction, resulting in an insufficient energy supply for conjugation. Collectively, ASK is a potential conjugative transfer inhibitor, providing novel strategies to prevent the spread of AMR.

A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall

The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here, we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.

A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall.

The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here, we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.

The molecular structure of an axle-less F1-ATPase

F1Fo ATP synthase is a molecular rotary motor that can generate ATP using a transmembrane proton motive force. Isolated F1-ATPase catalytic cores can hydrolyse ATP, passing through a series of conformational states involving rotation of the central γ rotor subunit and the opening and closing of the catalytic β subunits. Cooperativity in F1-ATPase has long thought to be conferred through the γ subunit, with three key interaction sites between the γ and β subunits being identified. Single molecule studies have demonstrated that the F1 complexes lacking the γ axle still “rotate” and hydrolyse ATP, but with less efficiency. We solved the cryogenic electron microscopy structure of an axle-less Bacillus sp. PS3 F1-ATPase. The unexpected binding-dwell conformation of the structure in combination with the observed lack of interactions between the axle-less γ and the open β subunit suggests that the complete γ subunit is important for coordinating efficient ATP binding of F1-ATPase.

Targeting the phosphatidylglycerol lipid: An amphiphilic dendrimer as a promising antibacterial candidate.

The rapid emergence and spread of multidrug-resistant bacterial pathogens require the development of antibacterial agents that are robustly effective while inducing no toxicity or resistance development. In this context, we designed and synthesized amphiphilic dendrimers as antibacterial candidates. We report the promising potent antibacterial activity shown by the amphiphilic dendrimer AD1b, composed of a long hydrophobic alkyl chain and a tertiary amine-terminated poly(amidoamine) dendron, against a panel of Gram-negative bacteria, including multidrug-resistant Escherichia coli and Acinetobacter baumannii. AD1b exhibited effective activity against drug-resistant bacterial infections in vivo. Mechanistic studies revealed that AD1b targeted the membrane phospholipids phosphatidylglycerol (PG) and cardiolipin (CL), leading to the disruption of the bacterial membrane and proton motive force, metabolic disturbance, leakage of cellular components, and, ultimately, cell death. Together, AD1b that specifically interacts with PG/CL in bacterial membranes supports the use of small amphiphilic dendrimers as a promising strategy to target drug-resistant bacterial pathogens and addresses the global antibiotic crisis.

Interaction between the electrochemical properties of powdered activated carbon and the biochemical processes within bacteria in Azo dye biodecolorization: An explanatory mechanism

Drawing on prior reports highlighting the redox mediator properties of powdered activated carbon (PAC), this study was designed to evaluate these properties to enhance the decolorization of azo dye by Klebsiella quasipneumoniae GT7. It was found that the presence of 0.5 % PAC in the medium increased the biodecolorization rate early in incubation. Chemical analysis revealed that dye conversion into aromatic amines occurred in microbial systems both with and without PAC. However, at initial dye concentrations (Cid) of 2 mM or higher, some dye remained on the PAC surface and in the medium. In contrast, the PAC-free system achieved nearly 100 % biodecolorization at all initial dye concentrations. The negative impact of PAC on decolorization efficiency in microbial systems with high initial dye concentrations cannot be solely explained by its redox mediator function. This study used the amphoteric-Donnan model for PAC's electrical double layer (EDL) and Mitchell's chemiosmotic model for bacterial proton motive force (PMF) to explore this. It found that charge storage in PAC's EDL regulates electron transfer fluxes, and proton species enhance the proton motive force across the bacterial membrane. These observations improve the understanding of PAC's role in microbial decolorization and its potential future applications.