Proteins In Bacterial Cells Research Articles

Ozonized water as pre-rinse and chlorhexidine as ultrasonic coolant: A Savoir-faire in times of covid-19

Background: Use of high speed ultrasonics work under high pressure which generates spatter and aerosols, contaminate the surroundings with various infectious agents. To reduce the infectious agents several procedures such as protective barriers, high volume evacuation device and prerinse. Ozonated water is antimicrobial and biocompatible making it suitable as pre-rinse dental use. Chlorhexidine is effective against broad spectrum bacteria attributing to its bicationic inhibitory action, bacterial cell protein chelation and high substantivity in the oral environment. This study aims to evaluate efficacy and microbial content of aerosols after prerinse with Ozonated water and 0.12% chlorhexidine as coolant in ultrasonic scalers.
 Methodology: 40 participants were assigned to each group randomly Group A, Group B, Group C and Group D. Blood agar plates were placed on the chest of patients before the start of procedure.
 Group A pre rinse+ Chlorhexidine as coolant
 Group B pre rinse+ Distilled Water as coolant
 Group C Chlorhexidine as coolant
 Group D Distilled Water as coolant
 After gravimetric settling, blood agar plates were transferred to the laboratory for incubation at 37°C for 48 h, followed by a colony‑counting procedure by the microbiologist.
 Results: Chlorhexidine as ultrasonic coolant with prerinse with ozonized water significantly reduces the microbial content of aerosols generated during scaling when compared with distilled water and without pre rinse.
 Conclusion: Prerinsing with efficient antimicrobial mouthrinse before dental procedure minimizes the risk of infectious agent cross-contamination in the dental operatory.

TOXIC SYMPTOMS IN WISTAR STRAIN RATS ON SINGLE AND REPEATED DOSAGE FROM THE EXTRACT OF RED BETEL LEAF (Piper crocatum) AS A TOXICITY TEST OF PERIODONTAL POCKET THERAPY

Red betel leaf (Piper crocatum) is one of the potential medicinal plants known to have properties to cure various diseases. The main components of betel leaf exhibit antiseptic, bactericidal, and antioxidant effects. The betel leaf was concentrated into an essential oil containing the antiseptic chemical. The antibacterial power of betel leaf essential oil is due to the content of phenolic compounds and their derivatives that can denature bacterial cell proteins, so it was considered to have potential as a material that could develop for periodontal therapy. After going through the stages of toxicity testing and repeated dose in terms of mortality, changes in body weight, and relative organ index of Wistar strain rats, the study continued to observe the effects that occurred after using single and repeated doses of 100, 400, and 1000 mg/kg BW in vivo using red betel leaf extract with the parameters of observing the behavior of rats studied for 14 days. Observation of the behavior of the test animals on toxic symptoms at each visit consisted of motor activity, straub phenomenon, piloerection, ptosis, corneal reflex, pineal reflex, lacrimation, vasodilation, catalepsy, dangling, reestablishment, walking backwards, circular walking, flexion, haffner, writhing, grooming, tremor, body shaking, vocalizations, urination, defecation, heart rate, salivation, mortality, posture, and breath changes before and after dosing for 14 days. From the observations, the analysis of the data obtained is primary data. Primary data in the form of qualitative data was obtained from data on effects that occurred after the rats were given a dose. After processing the data, the data is presented in tabular and narrative form based on the observations by showing the test dose used, the number of animals showing a toxic effect, the time of onset of a toxic effect and the percentage of animals in a group showing a toxic result. Based on the results of the study, red betel leaf extract with doses of 100, 400, and 1,000 mg/kg BW which was observed on the first and 14th days, did not cause toxic symptoms in all groups of rats, both on single administration and repeated administration for 14 days.

Mid-Infrared Photothermal-Fluorescence In Situ Hybridization for Functional Analysis and Genetic Identification of Single Cells.

Simultaneous identification and metabolic analysis of microbes with single-cell resolution and high throughput are necessary to answer the question of "who eats what, when, and where" in complex microbial communities. Here, we present a mid-infrared photothermal-fluorescence in situ hybridization (MIP-FISH) platform that enables direct bridging of genotype and phenotype. Through multiple improvements of MIP imaging, the sensitive detection of isotopically labeled compounds incorporated into proteins of individual bacterial cells became possible, while simultaneous detection of FISH labeling with rRNA-targeted probes enabled the identification of the analyzed cells. In proof-of-concept experiments, we showed that the clear spectral red shift in the protein amide I region due to incorporation of 13C atoms originating from 13C-labeled glucose can be exploited by MIP-FISH to discriminate and identify 13C-labeled bacterial cells within a complex human gut microbiome sample. The presented methods open new opportunities for single-cell structure-function analyses for microbiology.

Multifunctional tadpole-like bimetallic nanoparticles realizes synergistic sterilization with chemical kinetics and photothermal therapy

Bacterial infection has become a global health issue. The misuse of antibiotics has been resulting in increased drug resistance and bioaccumulation. Therefore, developing a highly safe antibacterial agent, with high antibacterial performance is demanding. Inspired by the natural motors performing automated tasks in complicated living environments, we demonstrate tadpole-like nanoparticles (TNPs) with several functions, including high photothermal conversion efficiency, peroxidase-like catalytic activity, glutathione peroxidase-like activity, and catalase-like activity. TNPs produce hydroxyl radical (•OH) at an extremely low concentration of hydrogen peroxide of 0.006%, which can damage bacterial cell membranes, proteins, and DNA. Moreover, the glutathione peroxidase-like activity disrupts the anti-oxidative mechanism of bacteria and improves the permeability of the cell membranes, consequently enhancing the killing effect of ROS. In addition, TNPs possess tadpole-like asymmetry to overcome Brownian motion, demonstrating strong directional motion propelled by O2. The in vivo experiments indicate that TNPs could also shorten the inflammatory period and promote angiogenesis, making them a very promising antibacterial agent.

Characterization of endotoxin free protein production of brain-derived neurotrophic factor (BDNF) for the study of Parkinson model in SH-SY5Y differentiated cells

Human neuronal cells are a more appropriate cell model for neurological disease studies such as Alzheimer and Parkinson's disease. SH-SY5Y neuroblastoma cells have been widely used for differentiation into a mature neuronal cell phenotype. The cellular differentiation process begins with retinoic acid incubation, followed by incubation with brain-derived neurotrophic factor (BDNF), a recombinant protein produced in E. coli cells. Endotoxin or lipopolysaccharide (LPS) is the major component of the outer membrane of bacterial cells that triggers the activation of pro-inflammatory cytokines and ultimately cell death. Consequently, any endotoxin contamination of the recombinant BDNF used for cell culture experiments would impact on data interpretation. Therefore, in this study, we expressed the BDNF recombinant protein in bacterial endotoxin-free cells that were engineered to modify the oligosaccharide chain of LPS rendering the LPS unable to trigger the immune response of human cells. The expression of DCX and MAP-2 in differentiated cells indicate that in-house and commercial BDNF are equally effective in inducing differentiation. This suggests that our in-house BDNF protein can be used to differentiate SH-SY5Y neuroblastoma cells without the need for an endotoxin removal step.

Antimicrobial Activity of Graphene Oxide Contributes to Alteration of Key Stress-Related and Membrane Bound Proteins.

Antibacterial activity of graphene oxide (GO) has been extensively studied, wherein penetration of the bacterial cell membrane and oxidative stress are considered to play a major role in the bactericidal activity of GO. However, the specific mechanism responsible for the antibacterial activity of GO remains largely unknown. Hence, the goal of this study was to explore the mode of action of GO, via an in-depth proteomic analysis of the targeted bacteria. Staphylococcus aureus was grown in the presence of GO and samples were collected at different growth phases to examine the cell viability and to analyze the changes in protein expression. Antimicrobial efficiency of GO was tested by assessing bacterial viability, live/dead staining and scanning electron microscopy. The intracellular reactive oxygen species (ROS) induced by GO treatment were examined by fluorescence microscopy. Label-free quantitative proteomics analysis was performed to examine the differentially regulated proteins in S. aureus after GO treatment. GO treatment was observed to reduce S. aureus viability, from 50 ± 17% after 4 h, to 93 ± 2% after 24 h. The live/dead staining confirmed this progressive antimicrobial effect of GO. SEM images revealed the wrapping of bacterial cells and their morphological disruption by means of pore formation due to GO insertion. GO treatment was observed to generate intracellular ROS, correlating to the loss of cell viability. The proteomics analysis revealed alteration in the expression of cell membrane, oxidative stress response, general stress response, and virulence-associated proteins in GO-treated bacterial cells. The time-dependent bactericidal activity of GO correlated with a higher number of differentially regulated proteins involved in the above.-mentioned processes. The obtained results suggest that the time-dependent bactericidal effect of GO is attributed to its wrapping/trapping ability, ROS production and due to physical disruption of the cell membrane.

Antibiotics: Precious Goods in Changing Times.

Antibiotics represent a first line of defense of diverse microorganisms, which produce and use antibiotics to counteract natural enemies or competitors for nutritional resources in their nearby environment. For antimicrobial activity, nature has invented a great variety of antibiotic modes of action that involve the perturbation of essential bacterial structures or biosynthesis pathways of macromolecules such as the bacterial cell wall, DNA, RNA, or proteins, thereby threatening the specific microbial lifestyle and eventually even survival. However, along with highly inventive modes of antibiotic action, nature also developed a comparable set of resistance mechanisms that help the bacteria to circumvent antibiotic action. Microorganisms have evolved specific adaptive responses that allow to appropriately react to the presence of antimicrobial agents, thereby ensuring survival during antimicrobial stress. In times of rapid development and spread of antibiotic(multi-)resistance, new resistance-breaking strategies to counteract bacterial infections are desperately needed. This chapter is an update to Chapter 1 of the first edition of this book and intends to give an overview of common antibiotics and their target pathways. It will also present examples for new antibiotics with novel modes of action, illustrating that nature's repertoire of innovative new antimicrobial agents has not been fully exploited yet, and we still might find new drugs that help to evade established antimicrobial resistance strategies.

Akkermansia Muciniphila as novel powerful bacterial player in colorectal cancer biotherapeutics

Colorectal cancer (CRC) is a fatal malignant tumor in the gastrointestinal region that is characterized by a weak prediction and the second leading reason for cancer death worldwide. Chemotherapy is common for progressive CRC patients, and 5-fluorouracil is commonly used in CRC therapy that inhibits cancer cell proliferation by suppressing DNA replication, but it can also cause the death of typical cells and hurt to normal tissues. Akkermansia muciniphila is an associate of the Verrucomicrobia phylum that plays a significant function in maintaining the mucosal layer of the human gastrointestinal region and by producing several mucolytic enzymes, it plays a substantial function in the degradation of mucin. Analysis of A. muciniphila bacterial cell proteins consisting of Amuc-1100, a thermostable OMP that reacts directly with the Toll like receptor (TLR)-2 and TLR-4 receptors and involved in immune responses that induce the production of interleukin (IL)-10, IL-1β, IL-6, IL-8, and tumor necrosis factor alpha in human-derived peripheral blood mononuclear cell (PBMCs). Amuc-1100 recovers the role of the metabolic endotoxemia in high-fat diet-induced fat mice and protects the growth of other commensal bacteria by inducing mucus production and promotes the production of immunoregulatory propionate. The importance of association among the therapeutic efficacy of immune checkpoint inhibitors therapy through modified gut microbiota in various tumors has been revealed. By the way, when the gastric levels of A. muciniphila were importantly enhanced in patients with CRC that have been related with positive antitumor immune responses in preclinical tumor models and patients with tumor they had a positive response to the immune therapy.

Design and synthesis of pyrazole, pyrazolone and 1,3,4-oxadiazole derivatives having pyrrole motif as a source of new antimicrobial and anticancer agents

As part of the study of pyrrole containing biheterocyclic derivatives we have synthesized different pyrrole-azole biheterocyclic derivatives: pyrrole-pyrazolones, pyrrole-pyrazoles and pyrrole 1,3,4 oxadiazoles have been synthesized using cyclization of pyrrolyl hydrazide-hydrazone intermediates in the presence of selected reagents. This work deals with structural clarification, NLO analysis and antimicrobial / anticancer activity evaluation of synthesized compounds. The structure of the pyrrole-azole derivatives were confirmed by modern spectroscopic methods. All quantum chemical calculations have been performed by density functional theory (DFT), using B3LYP functional and 6-311++G(d, p) as basis set. The calculated data corroborate well with the experimental data. The FT-IR analysis shows red shifts in vN–H and vCO stretching as result of dimer formation. The binding energies of dimer are found in the range of 12.75 - 11.21 kcal/mol after basis set superposition error. The UV–vis result shows major transparent over visible range enabling their suitability for application in the visible range. The optical energy gaps of these derivatives were found to be less than 3.2 eV. The β0 values for compounds (5a-b, 6a-b, 7a-b) are calculated as 24.61 × 10−30, 24.61 × 10−30, 42.510 × 10−30, 10.065 × 10−30, 19.146 × 10−30, 6.432 × 10−30 esu, respectively, indicating suitability for better non–linear optical response. All compounds (5a-b, 6a-6b, 7a-7b) have been screened against microbes and exhibited good antimicrobial activity. All compounds evaluated for their antiproliferative activity against two human cancer cell lines, i.e., HCT-116 (colon), and HL-60 (leukemia) cells. The compounds showed significant cytotoxicity against types of human cancer cell lines. In addition, the molecular docking studies have been achieved using 5b0e, 1i6w, 1q8i, 6p8u, bacterial, 6t1u, 1KS5 fungal and cancer cell protein 3QX3.

Extremely low frequency magnetic field enhances expression of a specific recombinant protein in bacterial host

Expression of proteins in bacterial host cells, particularly E.coli, has gained much attention in recent years. Low expression outcome is the main technical drawback associated with this procedure, further restricting its largescale application in industry. Therefore, application of new amendments or reformations are required before further proceedings. Extremely low frequency magnetic fields (ELF-MFs) have shown to significantly affect biological processes, including gene expression, in E.coli. In current study, we investigated whether application of ELF-MF could result in overexpression of proteins in E.coli or not. Cluster of differentiation-22 (CD22), as a model protein, was expressed in E.Coli Rosetta (DE3) under continuous exposure to ELF-MF after applying various concentrations of Isopropyl ß-d-1-thiogalactopyranoside (IPTG) (0.25–1.25 mM) as inducer. The strength and frequency of electromagnetic fields (EMFs) ranged between 15 and 100 mT and 2.5–20 Hz respectively. Interestingly, application of 55 mT EMFs with frequencies ranging from 2.5 to 2.8 Hz significantly enhanced the yield of expression at all studied IPTG concentrations. Contrarily, EMFs with intensities other than 55 mT meaningfully declined protein expression at IPTG concentrations equal to 1 and 1.25 mM. In conclusion, application of specific range of ELF-MFs may be exploited as a new modification for enhancing heterologous expression of proteins in E.coli.

A comprehensive review on mechanism of natural products against Staphylococcus aureus

The abuse of antibiotics seriously threatens the therapeutic effect. Natural products from plants, antimicrobial peptides and micro-organisms have antibacterial activity against Staphylococcus aureus . The mechanism of natural products reported in recent years on S. aureus includes six types, which are the acting on bacterial cell wall, cytomembrane, metabolic pathway, protein, nucleic acid, biofilm and quorum sensing system to achieve antibacterial effect. This article summarized the mechanism of natural products reported in recent years on S. aureus . It is found that the natural products acting on cell wall or cell wall synthesis pathway key enzymes are relatively safe and highly selective. It has the prospect of developing into medicine and provides the clue to investigate and utilize natural products in antibacterial activity.

Pseudomonas aeruginosa Bacterioferritin Is Assembled from FtnA and BfrB Subunits with the Relative Proportions Dependent on the Environmental Oxygen Availability.

Ferritins are iron storage proteins assembled from 24 subunits into a spherical and hollow structure. The genomes of many bacteria harbor genes encoding two types of ferritin-like proteins, the bacterial ferritins (Ftn) and the bacterioferritins (Bfr), which bind heme. The genome of P. aeruginosa PAO1 (like the genomes of many bacteria) contains genes coding for two different types of ferritin-like molecules, ftnA (PA4235) and bfrB (PA3531). The reasons for requiring the presence of two distinct types of iron storage protein in bacterial cells have remained largely unexplained. Attempts to understand this issue in P. aeruginosa through the recombinant expression of the ftnA and bfrB genes in E. coli host cells, coupled to the biochemical and structural characterization of the recombinant 24-mer FtnA and 24-mer BfrB molecules, have shown that each of the recombinant molecules can form an Fe3+-mineral core. These observations led to the suggestion that 24-mer FtnA and 24-mer BfrB molecules coexist in P. aeruginosa cells where they share iron storage responsibilities. Herein, we demonstrate that P. aeruginosa utilizes a single heterooligomeric 24-mer Bfr assembled from FtnA and BfrB subunits. The relative content of the FtnA and BfrB subunits in Bfr depends on the O2 availability during cell culture, such that Bfr isolated from aerobically cultured P. aeruginosa is assembled from a majority of BfrB subunits. In contrast, when the cells are cultured in O2-limiting conditions, the proportion of FtnA subunits in the isolated Bfr increases significantly and can become the most abundant subunit. Despite the variability in the subunit composition of Bfr, the 24-mer assembly is consistently arranged from FtnA subunit dimers devoid of heme and BfrB subunit dimers each containing a heme molecule.

Methyltransferase as Antibiotics Against Foodborne Pathogens: An In Silico Approach for Exploring Enzyme as Enzymobiotics.

The development of resistance in microbes against antibiotics and limited choice for the use of chemical preservatives in food lead the urgent need to search for an alternative to antibiotics. The enzymes are catalytic proteins that catalyze digestion of bacterial cell walls and protein requirements for the survival of the cell. To study methyltransferase as antibiotics against foodborne pathogen, the methyltransferase enzyme sequence was modeled and its interactions were analyzed against a membrane protein of the gram-positive and gram-negative bacteria through in silico protein–protein interactions. The methyltransferase interaction with cellular protein was found to be maximum, due to the maximum PatchDock Score (15808), which was followed by colicin (12864) and amoxicillin (4122). The modeled protein has found to be interact more significantly to inhibit the indicator bacteria than the tested antibiotics and antimicrobial colicin protein. Thus, model enzyme methyltransferase could be used as enzymobiotics. Moreover, peptide sequences similar to this enzyme sequence need to be designed and evaluated against the microbial pathogen.

Super-Resolution Microscopy and Tracking of DNA-Binding Proteins in Bacterial Cells.

The ability to detect individual fluorescent molecules inside living cells has enabled a range of powerful microscopy techniques that resolve biological processes on the molecular scale. These methods have also transformed the study of bacterial cell biology, which was previously obstructed by the limited spatial resolution of conventional microscopy. In the case of DNA-binding proteins, super-resolution microscopy can visualize the detailed spatial organization of DNA replication, transcription, and repair processes by reconstructing a map of single-molecule localizations. Furthermore, DNA-binding activities can be observed directly by tracking protein movement in real time. This allows identifying subpopulations of DNA-bound and diffusing proteins, and can be used to measure DNA-binding times in vivo. This chapter provides a detailed protocol for super-resolution microscopy and tracking of DNA-binding proteins in Escherichia coli cells. The protocol covers the genetic engineering and fluorescentlabeling of strains and describes data acquisition and analysis procedures, such as super-resolution image reconstruction, mapping single-molecule tracks, computing diffusion coefficients to identify molecular subpopulations with different mobility, and analysis of DNA-binding kinetics. While the focus is on the study of bacterial chromosome biology, these approaches are generally applicable to other molecular processes and cell types.

Antiadhesion and antibiofilm potential of Fagonia indica from Cholistan desert against clinical multidrug resistant bacteria

High resistance to antimicrobials is associated with biofilm formation responsible for infectious microbes to withstand severe conditions. Therefore, new alternatives are necessary as biofilm inhibitors to control infections. In this study, the antimicrobial and antibiofilm activities of Fagonia indica extracts were evaluated against MDR clinical isolates. The extract exhibited its antibiofilm effect by altering adherence and disintegration of bacterial cell wall. Fagonia indica has antibacterial effect as minimum inhibitory concentration (MIC) values ranging from 125 to 500 µg mL-1 and minimum bactericidal concentration (MBC) value was 500-3000 µg mL-1 against multidrug resistant (MDR) clinical isolates. The extract exhibited its antibiofilm effect by altering adherence and disintegration of bacterial cell wall. Fagonia indica had antibacterial effect as minimum inhibitory concentration (MIC) values ranging from 125 to 500 µg mL-1 and minimum bactericidal concentration (MBC) value was 500-3000 µg mL-1 against MDR isolates. The maximum inhibitory effects of Fagonia indica chloroform extract on biofilm formation was observed on Staphylococcus aureus (71.84%) followed by Klebsiella pneumoniae (70.83%) after 48 hrs showing that inhibition is also time dependent. Our results about bacterial cell protein leakage indicated that MDR isolates treated with chloroform extract of Fagonia indica showed maximum protein leakage of K. pneumoniae (59.14 µg mL-1) followed by S. aureus (56.7 µg mL-1). Cell attachment assays indicated that chloroform extract resulted in a 43.5-53.5% inhibition of cell adherence to a polystyrene surface. Our results revealed that extracts of Fagonia indica significantly inhibited biofilm formation among MDR clinical isolates, therefore, could be applied as antimicrobial agents and cost effective biofilm inhibitor against these MDR isolates.

Production of Properly Folded NS1 Protein in Bacterial Cells.

Dengue virus (DENV) NS1 protein is a multifunctional protein involved in several pathogenic processes but also has been described as a protective antigen suitable for eliciting humoral response against DENV. NS1 is essential for virus replication and can be found in different cell compartments and at different oligomeric states. It is secreted to the extracellular medium and can also be found circulating in the blood of infected patients, being routinely used as the serum biomarker for early dengue diagnosis. High-yield production of the recombinant NS1 protein in a native-like conformation is essential for studies regarding its function during DENV infection as well as to those interested in the development of new diagnostic approaches based on this protein. In this chapter, we describe an optimized protocol for high-yield expression of native-like NS1 in Escherichia coli bacterial cells.

The antibacterial mechanism of perilla rosmarinic acid.

Rosmarinic acid (RosA) is a phenolic acid compound extracted from perilla. In this experiment, the Oxford cup method was used to verify the antibacterial activity of PerillaRosA against Escherichia coli, Staphylococcus aureus, Salmonella, and Bacillus subtilis. By polyacrylamide gel electrophoresis, the effect of RosA on bacterial nucleic acid and bacterial Na+ /K+ -ATP-ase activity, and scanning electron microscope to exploration of its antibacterial mechanism preliminarily. The results showed that RosA had antibacterial properties against all four bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of E. coli were 0.8 and 0.9mg/ml, respectively. The MIC and MBC of Salmonella were 0.9 and 1.0mg/ml, respectively. The MIC and MBC of S. aureus and B. subtilis were both 1.0 and 1.1mg/ml. RosA has the bacteriostasis function, which can destroy bacterial cells and cell proteins and inhibit the activity of Na+ /K+ -ATP-ase in cells.

Surfaceome and Exoproteome Dynamics in Dual-Species Pseudomonas aeruginosa and Staphylococcus aureus Biofilms.

Bacterial biofilms are an important underlying cause for chronic infections. By switching into the biofilm state, bacteria can evade host defenses and withstand antibiotic chemotherapy. Despite the fact that biofilms at clinical and environmental settings are mostly composed of multiple microbial species, biofilm research has largely been focused on single-species biofilms. In this study, we investigated the interaction between two clinically relevant bacterial pathogens (Staphylococcus aureus and Pseudomonas aeruginosa) by label-free quantitative proteomics focusing on proteins associated with the bacterial cell surfaces (surfaceome) and proteins exported/released to the extracellular space (exoproteome). The changes observed in the surfaceome and exoproteome of P. aeruginosa pointed toward higher motility and lower pigment production when co-cultured with S. aureus. In S. aureus, lower abundances of proteins related to cell wall biosynthesis and cell division, suggesting increased persistence, were observed in the dual-species biofilm. Complementary phenotypic analyses confirmed the higher motility and the lower pigment production in P. aeruginosa when co-cultured with S. aureus. Higher antimicrobial tolerance associated with the co-culture setting was additionally observed in both species. To the best of our knowledge, this study is among the first systematic explorations providing insights into the dynamics of both the surfaceome and exoproteome of S. aureus and P. aeruginosa dual-species biofilms.

Bacterial Protein Homeostasis Disruption as a Therapeutic Intervention.

Cells have evolved a complex molecular network, collectively called the protein homeostasis (proteostasis) network, to produce and maintain proteins in the appropriate conformation, concentration and subcellular localization. Loss of proteostasis leads to a reduction in cell viability, which occurs to some degree during healthy ageing, but is also the root cause of a group of diverse human pathologies. The accumulation of proteins in aberrant conformations and their aggregation into specific beta-rich assemblies are particularly detrimental to cell viability and challenging to the protein homeostasis network. This is especially true for bacteria; it can be argued that the need to adapt to their changing environments and their high protein turnover rates render bacteria particularly vulnerable to the disruption of protein homeostasis in general, as well as protein misfolding and aggregation. Targeting bacterial proteostasis could therefore be an attractive strategy for the development of novel antibacterial therapeutics. This review highlights advances with an antibacterial strategy that is based on deliberately inducing aggregation of target proteins in bacterial cells aiming to induce a lethal collapse of protein homeostasis. The approach exploits the intrinsic aggregation propensity of regions residing in the hydrophobic core regions of the polypeptide sequence of proteins, which are genetically conserved because of their essential role in protein folding and stability. Moreover, the molecules were designed to target multiple proteins, to slow down the build-up of resistance. Although more research is required, results thus far allow the hope that this strategy may one day contribute to the arsenal to combat multidrug-resistant bacterial infections.

Photodynamic inactivation of planktonic Staphylococcus aureus by sodium magnesium chlorophyllin and its effect on the storage quality of lettuce.

Photodynamic inactivation (PDI) is a fast and effective non-heat sterilization technology. This study established an efficient blue light-emitting diode (LED) PDI with the photosensitizer sodium magnesium chlorophyllin (SMC) to eradicate Staphylococcus aureus in food. The antibacterial mechanisms were determined by evaluating DNA integrity, protein changes, morphological alteration, and the potency of PDI to eradicate S. aureus on lettuce was evaluated. Results showed that planktonic S. aureus could not be clearly observed on the medium after treatment with 5.0μmol/L SMC for 10min (1.14J/cm2). Bacterial cell DNA and protein were susceptible to SMC-mediated PDI, and cell membranes were found to be disrupted. Moreover, SMC-mediated PDI effectively reduced 8.31 log CFU/mL of S. aureus on lettuce under 6.84J/cm2 radiant exposure (30min) with 100μmol/L SMC, and PDI displayed a potent ability to restrain the weight loss as well as retard the changes of color difference of the lettuce during 7day storage. The study will enrich our understanding of the inactivation of S. aureus by PDI, allowing for the development of improved strategies to eliminate bacteria in the food industry.