Bacteria Cells Research Articles

Ionic liquid-derived carbon dots with enhanced antibacterial activity and antibiofilm capability for treatment of MRSA-infected wounds

Bacterial resistance to antibiotics has rendered bacterial infections an escalating threat to public health, prompting numerous researchers to strive towards the development of novel antimicrobial agents. Designable ionic liquids (ILs) have gained increasing prominence in the field of antibacterials. However, certain ILs exhibit suboptimal antimicrobial activity. In this study, we synthesized ionic liquid-derived carbon dots (IL-CDs: VOIMBr-CD) through vinyl and epoxy group reactions, resulting in enhanced antimicrobial efficacy. The VOIMBr-CD retains the antibacterial structure characteristic of ILs, including a positively charged imidazolium group and long alkyl chain. Moreover, VOIMBr-CD demonstrates selective antibacterial action against Staphylococcus aureus (S. aureus) while effectively inhibiting S. aureus biofilm growth. Notably, the antibacterial efficacy of VOIMBr-CD against methicillin-resistant Staphylococcus aureus (MRSA), surpasses vancomycin (Van). We conducted comprehensive investigations into the selective antibacterial mechanism of VOIMBr-CD which primarily involves electrostatic interactions, hydrophobic interactions, as well as generation of reactive oxygen species (ROS) within bacteria cells. In vivo experiments demonstrated that VOIMBr-CD significantly alleviate inflammation, facilitated collagen deposition and angiogenesis, and effectively expedited wound healing in MRSA-infected mice models; thus, highlighting their potential as therapeutic candidates for diseases resembling MRSA infection-like conditions. Importantly, this work presents a novel approach utilizing IL-based materials for developing effective antibacterials thereby offering new insights into the application prospects of IL-derived materials.

The Toxin of VapBC-1 Toxin-Antitoxin Module from Leptospira interrogans Is a Ribonuclease That Does Not Arrest Bacterial Growth but Affects Cell Viability.

Bacterial ubiquitous Toxin-Antitoxin (TA) systems are considered to be important survival mechanisms during stress conditions. In regular environmental conditions, the antitoxin blocks the toxin, whereas during imbalanced conditions, the antitoxin concentration decreases, exposing the bacteria cell to a range of toxic events. The most evident consequence of this disequilibrium is cell growth arrest, which is the reason why TAs are generally described as active in the function of bacterial growth kinetics. Virulence-associated proteins B and C (VapBC) are a family of type II TA system, in which VapC is predicted to display the toxic ribonuclease activity while VapB counteracts this activity. Previously, using in silico data, we designated four VapBC TA modules in Leptospira interrogans serovar Copenhageni, the main etiological agent of human leptospirosis in Brazil. The present study aimed to obtain the proteins and functionally characterize the VapBC-1 module. The expression of the toxin gene vapC in E. coli did not decrease the cell growth rate in broth culture, as was expected to happen within active TA modules. However, interestingly, when the expression of the toxin was compared to that of the complexed toxin and antitoxin, cell viability was strongly affected, with a decrease of three orders of magnitude in colony forming unity (CFU). The assumption of the affinity between the toxin and the antitoxin was confirmed in vivo through the observation of their co-purification from cultivation of E. coli co-expressing vapB-vapC genes. RNAse activity assays showed that VapC-1 cleaves MS2 RNA and ribosomal RNA from L. interrogans. Our results indicate that the VapBC-1 module is a potentially functional TA system acting on targets that involve specific functions. It is very important to emphasize that the common attribution of the functionality of TA modules cannot be defined based merely on their ability to inhibit bacterial growth in a liquid medium.

The use of mare's milk for yogurt ice cream and synbiotic ice cream production.

During the last years, growing interest in the use of mare's milk in food production is observed. The subject of the study was to evaluate the feasibility of mare's milk for the production of yogurt ice cream and synbiotic ice cream. Four variants of mare's milk ice cream were developed: ice cream with yogurt bacteria without inulin (YO) and with 2% of inulin (YO+I), synbiotic ice cream with 2% inulin and Lacticaseibacillus rhamnosus (LCR+I) and with Lactiplantibacillus plantarum (LP+I). Ice creams were enriched with inulin in order to evaluate its influence on the viability of LAB and on the product quality. Physicochemical, textural and sensory analyses were performed. Count of viable bacteria cells was also evaluated. Obtained ice creams did not differ in terms of protein, fat and total solids content (1.85-1.91%, 7.33-7.58% and 24.66-26.96% respectively), but differed in acidity. Ice cream YO, the only one without inulin, had the highest acidity, what suggests that inulin decrease this parameter. Regardless the type of LAB starter culture and inulin addition, samples had the same range of overrun (35.20-44.03%) and melting rate (73.49-79.87%). However the variant of ice cream influenced textural properties and colour parameters. All obtained mare's milk ice creams had high overall sensory quality. It was noticed, that ice cream with inulin had higher count of LAB (>7logCFU/g), than sample without inulin (>6logCFU/g). In conclusion, mare's milk may be considered as feasible raw material for yogurt ice cream and synbiotic ice cream production.

Characterization and application of LysSGF2 and HolSGF2 as potential biocontrol agents against planktonic and biofilm cells of common pathogenic bacteria

Antimicrobial resistance represents a global health emergency, necessitating the introduction of novel antimicrobial agents. In the present study, lysozyme and holin from Shigella flexneri 1.1868 phage SGF2, named LysSGF2 and HolSGF2, respectively, were cloned, expressed, and characterized. LysSGF2 and HolSGF2 showed lytic activities against S. flexneri 1.1868 cells at 4–55 °C and pH 3.1–10.3. LysSGF2 exhibited antimicrobial activity against five gram-negative and two gram-positive bacteria. HolSGF2 showed antimicrobial activity against four gram-negative and one gram-positive species. The antibacterial activities of LysSGF2 and HolSGF2 were determined in liquid beverages, including bottled water and milk. The relative lytic activity of LysSGF2 combined with HolSGF2 against the tested bacteria was approximately 46–77 % in water. Furthermore, the combination markedly decreased the viable counts of tested bacteria by approximately 3–5 log CFU/mL. LysSGF2 and HolSGF2 could efficiently remove biofilms on polystyrene, glass, and stainless-steel. The efficacy of the LysSGF2 and HolSGF2 combination against the tested bacteria on polystyrene was 58–71 %. Combination treatment effectively killed biofilm cells formed on stainless-steel and glass by 1–4 log CFU/mL. ese results indicate that LysSGF2 and HolSGF2 can successfully control both the planktonic and biofilm cells of common pathogenic bacteria, suggesting that the combined or single use of LysSGF2 and HolSGF2 may be of great value in food processing.

Biofortification, metabolomic profiling and quantitative analysis of vitamin B12 enrichment in guava juice via lactic acid fermentation using Levilactobacillus brevis strain KU15152.

Chemical fortification and dose supplementation of vitamin B12 are widely implemented to combat deficiency symptoms. However, in situ, fortification of vitamin B12 in food matrixes can be a promising alternative to chemical fortification. The present study aimed to produce vitamin B12-rich, probiotic guava juice fermented with Levilactobacillus brevis strain KU15152. Pasteurized fresh guava juice was inoculated with 7.2 log CFU mL-1 L. brevis strain KU15152 and incubated for 72 h at 37 °C anaerobically. The antioxidants, total phenolic compounds, vitamin B12 production, sugars, organic acids, pH and viable count were analyzed at 24, 48 and 72 h of incubation. The fermented juice was stored at 4 °C, and the changes in its functional properties were analyzed at 7-day intervals up to 28 days of storage. During fermentation, the bacteria cell count was increased from 7.01 ± 0.06 to 9.76 ± 0.42 log CFU mL-1 after 72 h of fermentation and was decreased to 6.94 ± 0.34 CFU mL-1 during storage at 4 °C after 28 days. The pH, total soluble solids, crude fiber, citric acid and total sugars decreased, while titratable acidity, total protein, antioxidants, phenolic compounds and lactic acid contents increased during fermentation. The fermented guava juice exhibited higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS)) radical scavenging activities (85.97% and 75.97%, respectively) at 48 h of fermentation. The concentration of active vitamin B12 in the sample reached 109.5 μg L-1 at 72 h of fermentation. However, this concentration gradually decreased to 70.2 μg L-1 during the storage period. During storage for 28 days at 4 °C, both the fermented and control guava juices exhibited a decline in antioxidant and phenolic compound concentrations. Furthermore, the addition of 20% honey and guava flavor enhanced the organoleptic properties and acceptability of fermented guava juice. The value-added fermented guava juice could be a novel functional food product to combat vitamin B12 deficiency. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Silver Nanoparticles Loaded With Oleuropein Alleviates LPS-Induced Acute Lung Injury by Modulating the TLR4/P2X7 Receptor-Mediated Inflammation and Apoptosis in Rats.

Toll-like receptor 4 (TLR-4) ligands were initially shown to be the source of lipopolysaccharide (LPS), a gram-negative bacterium's cell wall immunostimulatory component. Oxidative stress, apoptosis, and inflammation are all potential effects of LPS treatment on the lungs. By triggering oxidative stress and inflammation, these negative effects could be avoided. Robust flavonoid oleuropein (OLE) exhibits anti-inflammatory, antiproliferative, and antioxidative properties. A nanodelivery system could improve its low bioavailability, making it more effective and useful in treating chronic human ailments. This study evaluates the effects of AgNP-loaded OLE on LPS-induced lung injury in rats in terms of TLR4/P2X7 receptor-mediated inflammation and apoptosis. Forty-eight male albino rats were randomly divided into eight groups. Drugs were administered to the groups in the doses specified as follows: Control, LPS (8 mg/kg ip), OLE (50 mg/kg) AgNPs (100 mg/kg), OLE + AgNPs (50 mg/kg), LPS + OLE (oleuropein 50 mg/kg ig + LPS 8 mg/kg ip), LPS + AgNPs (AgNPs 100 mg/kg ig + LPS 8 mg/kg ip), and LPS + OLE + AgNPs (OLE + AgNPs 50 mg/kg + LPS 8 mg/kg ip). After the applications, the rats were decapitated under appropriate conditions, and lung tissues were obtained. Oxidative stress (SOD, MDA, and GSH), and inflammation (IL-6, IL-1β, TNF-α, Nrf2, P2X7R, AKT, and TLR4) parameters were evaluated in the obtained lung tissues. Additionally, histopathology studies were performed on lung tissue samples. The data obtained were evaluated by comparison between groups. Both OLE and OLE + AgNPs showed potential in reducing oxidative stress, inflammation, and apoptosis (p < 0.05). These findings were supported by histopathological analysis, which revealed that tissue damage was reduced in OLE and OLE + AgNPs-treated groups. According to the results, LPS-induced lung injury can be reduced by using nanotechnology and producing OLE + AgNP.

Evaluating C18 stationary phases with a positively charged surface for proteomic LC-MS applications using mobile phase acidified with reduced formic acid concentration

We have recently demonstrated the ability of a C18 stationary phase with a positively charged surface (PCS-C18) to provide superior chromatographic separation of peptides using mobile phase acidified with a mere 0.01 % formic acid, significantly improving MS sensitivity. Here, we examined three columns packed with different PCS-C18 phases using the MS-favorable mobile phase acidified with low formic acid concentrations to establish the impact of separation performance and better MS sensitivity on peptide identifications. The surface charge interaction was evaluated using the retention of nitrate. The highest interaction was observed for the AdvanceBio Peptide Plus column. A surface charge-dependent shift in the retention time of peptides was confirmed with a change in formic acid concentration in the mobile phase. The separation performance of the columns with MS-favorable mobile phase acidified with low concentrations of formic acid was evaluated using well-characterized peptides. The loading capacity was assessed using a basic peptide with three lysine residues. Good chromatographic peak shapes and high loading capacity were observed for the Acquity Premier CSH C18 column, even when using a mobile phase acidified with 0.01 % formic acid. The extent of improvement in peptide identification when using reduced formic acid concentration was evaluated by analyzing the tryptic digest of trastuzumab and tryptic digest of whole bacteria cell lysate. Each column provided improved MS signal intensity and peptide identification when using the mobile phase with 0.01 % formic acid. The ability of the Acquity Premier CSH C18 column to provide better separation of peptides, even with a reduced formic acid concentration in the mobile phase, boosted MS signal intensity by 65 % and increased the number of identified peptides from the bacterial sample by 19 %. Our study confirms that significant improvement in the proteomic outputs can be achieved without additional costs only by tailoring the chemistry of the stationary phase to the composition of the mobile phase. Our results can help researchers understand the retention mechanism of peptides on the PCS-C18 stationary phases using low-ionic strength mobile phases and, more importantly, select the best-suited stationary phases for their LC-MS proteomic applications.

High-speed cryo-microscopy reveals that ice-nucleating proteins of Pseudomonas syringae trigger freezing at hydrophobic interfaces.

Ice-nucleating proteins (INpro) trigger the freezing of supercooled water droplets relevant to atmospheric, biological, and technological applications. The high ice nucleation activity of INpro isolated from the bacteria Pseudomonas syringae could be linked to the aggregation of proteins at the bacterial membrane or at the air-water interface (AWI) of droplets. Here, we imaged freezing onsets, providing direct evidence of these proposed mechanisms. High-speed cryo-microscopy identified the onset location of freezing in droplets between two protein-repellent glass slides. INpro from sterilized P. syringae (Snomax) statistically favored nucleation at the AWI of the droplets. Removing cellular fragments by filtration or adding surfactants increased the frequency of nucleation events at the AWI. On the other hand, cultivated intact bacteria cells or lipid-free droplets nucleated ice without an affinity to the AWI. Overall, we provide visual evidence that INpro from P. syringae trigger freezing at hydrophobic interfaces, such as the AWI or the bacterial membrane, with important mechanistic implications for applications of INpro.

Effects of flow-induced electromagnetic field and surface roughness on antifouling activity of phenolic compounds

Microbial fouling involves the physicochemical interactions between microorganisms and solid surfaces. An electromagnetic field (EMF) may change the diffusion rates of microbial cells and the electrical double layer around the cells and contacting surfaces. In the current study, polycardanol exhibiting antibiofouling activity was modified with ferromagnetic iron oxide (IO) to investigate the EMF effects on bacterial adhesion. When there was a flow of electrolyte that contained bacterial cells, flow-induced EMF was generated according to Faraday’s principle. It was observed that the IO-ionic solution (IS)-modified surfaces, with an induced current of 44, 53, 66 nA, showed decreases in the adhesion of bacteria cells more than the unmodified (polycardanol) and IO-nanoparticles-modified ones. In addition to the EMF effects, the nano-scale uniform roughness of the modified surfaces appeared to play an important role in the reduction of cell adhesion. The results demonstrated that the IOIS-modified surface (3.2 × 10−6 mM IO) had the highest antibiofouling activity.

Identifying antibiotic-resistant strains via cell sorting and elastic-light-scatter phenotyping

The proliferation and dissemination of antimicrobial-resistant bacteria is an increasingly global challenge and is attributed mainly to the excessive or improper use of antibiotics. Currently, the gold-standard phenotypic methodology for detecting resistant strains is agar plating, which is a time-consuming process that involves multiple subculturing steps. Genotypic analysis techniques are fast, but they require pure starting samples and cannot differentiate between viable and non-viable organisms. Thus, there is a need to develop a better method to identify and prevent the spread of antimicrobial resistance. This work presents a novel method for detecting and identifying antibiotic-resistant strains by combining a cell sorter for bacterial detection and an elastic-light-scattering method for bacterial classification. The cell sorter was equipped with safety mechanisms for handling pathogenic organisms and enabled precise placement of individual bacteria onto an agar plate. The patterning was performed on an antibiotic-gradient plate, where the growth of colonies in sections with high antibiotic concentrations confirmed the presence of a resistant strain. The antibiotic-gradient plate was also tested with an elastic-light-scattering device where each colony’s unique colony scatter pattern was recorded and classified using machine learning for rapid identification of bacteria. Sorting and patterning bacteria on an antibiotic-gradient plate using a cell sorter reduced the number of subculturing steps and allowed direct qualitative binary detection of resistant strains. Elastic-light-scattering technology is a rapid, label-free, and non-destructive method that permits instantaneous classification of pathogenic strains based on the unique bacterial colony scatter pattern.Key points• Individual bacteria cells are placed on gradient agar plates by a cell sorter• Laser-light scatter patterns are used to recognize antibiotic-resistant organisms• Scatter patterns formed by colonies correspond to AMR-associated phenotypes

Comparing Antimicrobial Effects of Heterotrigona itama Propolis from Two Regions of Malaysia Against Enterococcus faecalis

Objective: This present study aimed to determine and compare the antimicrobial properties of Malaysian propolis (MP) produced by Heterotrigona Itama from different regions of Malaysia, against E. faecalis. Methods: The propolis were obtained in Lenggong MLP (North Peninsula Malaysia) and Raub MRP - (Central Peninsula Malaysia). The antibacterial activities of the ethanolic extracts of propolis were conducted using antimicrobial susceptibility test (AST), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The effect of these extracts on the cell morphology were observed using scanning electron microscopy (SEM). Calcium hydroxide and 5% dimethyl sulfoxide (DMSO) were used as controls. Results: Statistical analysis was done using unpaired t-test to differentiate the difference of the two averages. The ethanol extracts of MLP showed higher activity compared to MRP at 50mg/ml on E. faecalis with zone of inhibition of 14.33mm and 10.00mm respectively. MIC test for MRP and MLP was 0.78125mg/ml and 3.125mg/ml respectively. Whereas the MBC value for both MRP and MLP was 12.50mg/ml and 50.00mg/ml respectively. SEM analysis showed that MP disrupted the size, cell morphology and the structure of the bacteria cell wall. Conclusion: Our study showed MRP outperformed MLP against E. faecalis via MIC, MBC and SEM. Dissimilarities of surrounding trees in Raub and Lenggong may provide the variable chemical source contributing to this contrast. Thus, these stingless bees have a very special relationship with plant resins, relying on them for the very survival of their nests.

Multiple factors trigger the formation and resuscitation of the VBNC state in alcohol-producing Klebsiella pneumoniae.

Klebsiella pneumoniae can enter a viable but nonculturable (VBNC) state to survive in unfavorable environments. Our research found that high-, medium-, and low-alcohol-producing K. pneumoniae strains are associated with nonalcoholic fatty liver disease. However, the presence of the three Kpn strains has not been reported in the VBNC state or during resuscitation. In this study, the effects of different strains, salt concentrations, oxygen concentrations, temperatures, and nutrients in K. pneumoniae VBNC state were evaluated. The results showed that high-alcohol-producing K. pneumoniae induced a slower VBNC state than medium-alcohol-producing K. pneumoniae, and low-alcohol-producing K. pneumoniae. A high-salt concentration and micro-oxygen environment accelerated the loss of culturability. Simultaneously, both real-time quantitative PCR and droplet digital PCR were developed to compare the quantitative comparison of three Kpn strain VBNC states by counting single-copy gene numbers. At 22°C or 37°C, the number of culturable cells decreased significantly from about 108 to 105-106 CFU/mL. In addition, imipenem, ciprofloxacin, polymyxin, and phiW14 inhibited cell resuscitation but could not kill VBNC-state cells. These results revealed that the different environments evaluated play different roles in the VBNC induction process, and new effective strategies for eliminating VBNC-state cells need to be further studied. These findings provide a better understanding of VBNC-state occurrence, maintenance, detection, and absolute quantification, as well as metabolic studies of resuscitation resistance and ethanol production.IMPORTANCEBacteria may enter VBNC state under different harsh environments. Pathogenic VBNC bacteria cells in clinical and environmental samples pose a potential threat to public health because cells cannot be found by routine culture. The alcohol-producing Kpn VBNC state was not reported, and the influencing factors were unknown. The formation and recovery of VBNC state is a complete bacterial escape process. We evaluated the influence of multiple induction conditions on the formation of VBNC state and recovery from antibiotic and bacteriophage inhibition, and established a sensitive molecular method to enumerate the VBNC cells single-copy gene. The method can improve the sensitivity of pathogen detection in clinical, food, and environmental contamination monitoring, and outbreak warning. The study of the formation and recovery of VBNC-state cells under different stress environments will also promote the microbiological research on the development, adaptation, and resuscitation in VBNC-state ecology.

Insights into the Versatility of Using Atomic Absorption Spectrometry in Antibacterial Research.

The ongoing development of bacterial resistance to antibiotics is a global challenge. Research in that field is thus necessary. Analytical techniques are required for such a purpose. From this perspective, the focus was on atomic absorption spectrometry (AAS). Although it is old, AAS often offers unexpected potential. Of course, this should be exploited. The aim was therefore to demonstrate the versatility of the technique in antibacterial research. This is illustrated by various examples of its practical application. AAS can be used, for example, to confirm the identity of antibacterial compounds, for purity controls, or to quantify the antibiotics in pharmaceutical preparations. The latter allowed analysis without laborious sample preparation and without interference from other excipients. In addition, AAS can help elucidate the mode of action or resistance mechanisms. In this context, quantifying the accumulation of the antibiotic drug in the cell of (resistant) bacteria appears to play an important role. The general application of AAS is not limited to metal-containing drugs, but also enables the determination of some organic chemical antibiotics. Altogether, this perspective presents a range of applications for AAS in antibacterial research, intending to raise awareness of the method and may thus contribute to the fight against resistance.

Generic viability qPCR for monitoring shelf life of microbial biological control agents coated on seeds based on the nucleic acid intercalating dyes EMA and PMAxx

Biological control of seedborne pathogens and soilborne seedling pathogens through antagonists applied on seeds is an alternative to chemical seed treatments. Information on the viability of inocula on treated seeds is essential for any development and use of beneficial fungi or bacteria on seeds. Generic fungal and bacterial qPCR assays were combined with the nucleic acid intercalating dyes ethidium monoazide (EMA) and propidium monoazide (PMAxx) for the quantification of viable cells of fungi and bacteria on seeds. The applied protocols for generic fungal viability qPCR (v-qPCR) in combination with EMA and PMAxx and for generic bacterial v-qPCR in combination with PMAxx allowed the viability quantification of fungal and bacterial isolates representing a broad range of species with the exception of fungal species with highly melanized conidia. A first application of v-qPCR to coated seeds of onion and spinach indicated a differential plant species effect on survival of a coated fungus and a yeast with a generally better survival on seeds of spinach compared to seeds of onions and a similar good survival of the bacterium L. enzymogenes 3.1T8 on both seed types. The v-qPCR protocols can be applied in screening assays aiming at the selection of new antagonists with higher survival potentials and the development of new seed processing technologies compatible with coated antagonists.

Galactofuranans and Galactomannan of Cell Walls as Chemotaxonomic Characteristics of the Genus and Species of &lt;i&gt;Clavibacter&lt;/i&gt;

Two types of glycopolymers of different structures were found in the cell walls of type strains of two species of phytopathogenic bacteria, Clavibacter insidiosus VKM Ac-1402T and Clavibacter nebraskensis VKM Ac-1404T (family Microbacteriaceae, class Actinomycetes). The first type is represented by new, previously undescribed (1→6)-linked β-D-galactofuranans, which differ in the studied strains of the two species by the structure of side oligosaccharide chains (the structures are given in the text). The structure of the second glycopolymer, pyruvate-containing galactomannan, was identical in both strains. The results obtained in this work, together with those previously obtained, indicate that the presence of pyruvate-containing galactomannan and galactofuranans with an identical core structure and different oligosaccharide side substituents can be considered as a chemotaxonomic trait of the genus Clavibacter, and galactofuranans with di-, tri-, or tetrasaccharide substituents of different composition and structures can serve as chemotaxonomic markers of species. The data obtained expand our understanding of the structural diversity of natural glycopolymers and structural features of the bacteria cell walls of various taxa and may be of interest for taxonomic studies and studies aimed at elucidating the molecular mechanisms of interaction between bacteria and plant cells.

Medical Scope of Biofilm and Quorum Sensing during Biofilm Formation: Systematic Review

Biofilms are accumulations of microorganisms in an extracellular polymeric substance matrix which are composed of polysaccharides, proteins, lipids, and nucleic acids. Many bacteria can switch between a planktonic form and a biofilm form. The planktonic bacteria have relatively high cell growth and reproduction rates and have a reduced likelihood of survival but can adapt to occupy new habitats. The biofilm state appears to be a natural and predominant state of bacteria. The need for the formation of bacterial biofilm is that it enhances the tolerance of bacteria to harsh environmental conditions, thereby allowing bacteria to avoid being washed away by water flow or the bloodstream by simply attaching to a surface or tissue, and the EPS matrix protects bacteria cells, in deeper layers, against antimicrobial agents, probably by limiting the diffusion of these agents. Biofilm formation steps are initial contact/attachment to the surface, followed by micro-colony formation, maturation and formation of the architecture of the biofilm, and finally detachment/dispersion of the biofilm. Once formed, biofilm restricts bacterial mobility and increases cell density. Secretions of autoinducers into the environment are critical for cross-signaling between bacteria. This cross-talk is called quorum sensing (QS). Quorum sensing is a cell–cell communication mechanism between bacteria that allows specific processes to be controlled, such as biofilm formation and virulence factor expression. Bacterial quorum sensing signaling mainly consists of acyl-homoserine lactones (produced by Gram-negatives), autoinducing peptides (produced by Gram-positives), and autoinducer-2 (produced by both Gram-negatives and Gram-positives). Therefore, this review is aimed at how bacterial biofilms work and are formed.

Impact of ZnO nanoparticles on Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposites as antibacterial agents and drug loading materials

A series of Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposites were successfully synthesized using the hydrothermal method with different ZnO masses. The novelty of this study was the obtained Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposite as a good candidate as an antibacterial agent and drug delivery material. The IR spectra showed that the samples were successfully formed. The vibrations of Fe–O and Mn–O were detected at 678.94–563.21cm−1, and that of Zn–O was located at 933.55–867.97cm−1. Meanwhile, the XRD pattern showed that the samples have two crystal phases, i.e. magnetite and ZnO. The nanostructure of the samples was studied by SAXS, showing that the Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposite formed clustering particles that were structured by secondary and primary particles. The secondary particles in the samples contained about 3–4 primary particles. The magnetic properties were characterized using VSM, showing that the samples have superparamagnetic behavior. The increase in ZnO mass affected the saturation magnetization value. The highest saturation magnetization value was approximately 8.66 emu/g for the sample with the smallest ZnO mass. The samples contained Fe2+, Fe3+, and ZnO2+ ions, which created oxidative stress that damaged the DNA cells of bacteria, as seen from the results of the antibacterial activity test. In addition, it was found that the Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposite has another potential as a drug loader material. As the ZnO mass increased, the drug loading efficiency also increased up to 75%. Thus, the prepared Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposites have potential as antibacterial agents and drug loading materials.

Template bacteria-free fabrication of surface imprinted polymer-based biosensor for E. coli detection using photolithographic mimics: Hacking bacterial adhesion

As one class of molecular imprinted polymers (MIPs), surface imprinted polymer (SIP)-based biosensors show great potential in direct whole-bacteria detection. Micro-contact imprinting, that involves stamping the template bacteria immobilized on a substrate into a pre-polymerized polymer matrix, is the most straightforward and prominent method to obtain SIP-based biosensors. However, the major drawbacks of the method arise from the requirement for fresh template bacteria and often non-reproducible bacteria distribution on the stamp substrate. Herein, we developed a positive master stamp containing photolithographic mimics of the template bacteria (E. coli) enabling reproducible fabrication of biomimetic SIP-based biosensors without the need for the “real” bacteria cells. By using atomic force and scanning electron microscopy imaging techniques, respectively, the E. coli-capturing ability of the SIP samples was tested, and compared with non-imprinted polymer (NIP)-based samples and control SIP samples, in which the cavity geometry does not match with E. coli cells. It was revealed that the presence of the biomimetic E. coli imprints with a specifically designed geometry increases the sensor E. coli-capturing ability by an “imprinting factor” of about 3. These findings show the importance of geometry-guided physical recognition in bacterial detection using SIP-based biosensors. In addition, this imprinting strategy was employed to interdigitated electrodes and QCM (quartz crystal microbalance) chips. E. coli detection performance of the sensors was demonstrated with electrochemical impedance spectroscopy (EIS) and QCM measurements with dissipation monitoring technique (QCM-D).

Characterization of 20 μm Dielectrophoretic Interelectrode Gap for Staphylococcus Aureus Rapid Detection Application

We propose an improvement of dielectrophoresis technique (DEP) by designing, simulating and experiment a 20 μm interelectrode gap for Staphylococcus aureus rapid detection application. In this paper, we use MyDEP simulation for DEP polarization Staphylococcus aureus on frequencies range. COMSOL simulation is utilized for comparison of 20 μm and 80 μm interelectrode gap based on trajectory and velocity of particles for Staphylococcus aureus application. We implied 20 μm interelectrode gap for Staphylococcus aureus application produced higher magnitude DEP force. Which gives accurate trajectory characterization and higher velocity of particle movement. DEP characterization using small interelectrode gap is capable of producing stable and optimum DEP value. It is demanding to distinguish the simulation Staphylococcus aureus using experimental method. DEP technique is important for analysis and characterization of the bacteria. The result show that 20 μm interelectrode gap has higher intensity of electric field which is 1.51 x 10^6 V/m in COMSOL simulation and produced 20.1 m/s for velocity of particle trajectories which is higher compared to 80 μm interelectrode gap. The DEP response was tested on 2.5 MHz, as crossover frequency response was observed on experimental and simulation. Thus, supportsthe capability of 20 μm interelectrode gap for Staphylococcus aureus rapid detection application. Furthermore, DEP characterization can be improvised by focusing on interelectrode gap for characterization among bacteria cells, critical for bacteria detection, manipulation, and isolation.

Procedure for rapid determination of bile-tolerant gram-negative bacteria in drugs

The European Pharmacopoeia is a single reference study for the quality control of drugs. The official standards published within it provide a legal and scientific basis for quality control in the processes of drugs development, production and marketing. However, the long experience and the multitude of studies have demonstrated that medicinal forms represent unstable dispersed systems and can undergo various manifest or non-manifest changes, leading to drug incompatibilities. Along with the physico-chemical transformations, microbiological transformations can occur with the contamination of the final product with pathogenic, conditionally pathogenic or even saprophytic germs, especially medicines that do not undergo final sterilization or are not aseptically prepared. Microbial contamination of the drug can be an indicator of the production conditions; it can cause the instability of the product through the microbial decomposition of auxiliary substances, the alteration or definitive cancellation of the therapeutic effect of the active substances, the appearance of metabolites with toxic properties, especially those fractions of endotoxins on the wall cell of gram-negative bacteria with the development of allergenic, pyrogenic substances and the induction of the danger of local orgeneral infections. An important role is attributed to the group of bile-tolerant gram-negative bacteria as representatives of microorganisms that are inadmissible in one g/ml for the absence test and for the quantitative test &lt;10 NCP/g/ml (probable number of bacteria), inadmissible in non-sterile medicinal products, herbal medicinal products for oral use and extracts used in their preparation. Due to the diversity of medicinal forms in terms of content, method of application, and therapeutic action, these preparations fulfil the indispensable conditions for the growth of microorganisms, therefore a primary concern is to avoid microbial contamination from the technological phase to the administration phase in order to prevent complications associated with bacterial infections. The given study reveals the testing of the procedure for the rapid determination of inadmissible microorganisms in non-sterile medicinal products and herbal drugs for oral use and the extracts used in their preparation, especially microorganisms of the group Enterobacteriaceae spp.