Bacterial Cells Research Articles

Biochar: Preserving the Long-Term Catalytic Activity of Biosynthesized PdNPs/AuNPs in Cr(VI) Reduction

Palladium nanoparticles (PdNPs) and gold nanoparticles (AuNPs) synthesized within yeast biomass can be effectively preserved in yeast biochar while maintaining their catalytic activity. Herein, we observe well-preserved PdNPs/AuNPs within yeast biochars, alongside the retention of cell morphology. Notably, the crystal structures of AuNPs within biochars exhibit similarity to that of uncarbonized samples, suggesting minimal influence of carbonization on nanoparticle structure. XPS analysis reveals the transformation of organic bacterial cells into heterocyclic aromatic-carbon material during pyrolytic carbonization. Chemical states analysis indicates the prevalence of metallic Pd(0)/Au(0) with limited PdOx/AuOx content in yeast biochars. FTIR analysis highlights increased aromaticity of biochars with typical bands for aromatic ring, and new bands appeared in Pd/Au-loaded biochars possibly attribute to PdOx/AuOx. Moreover, yeast biochars exhibit significantly improved Cr(VI) removal capacities compared to yeast biomass. Specifically, we detect complete removal within 18h for CYPd and CYPdG biochars, contrasting with less than 65% removal efficiency in yeast biomass. These findings underscore the potential of carbonization in enhancing the long-term catalytic activity of biosynthesized PdNPs/AuNPs for efficient Cr(VI) reduction, offering promising avenues for environmental remediation strategies.

Probing Peptidoglycan Synthesis in the Gut Commensal Akkermansia Muciniphila with Bioorthogonal Chemical Reporters.

Our gut microbiota directly influences human physiology in health and disease. The myriad of surface glycoconjugates in both the bacterial cell envelope and our gut cells dominate the microbiota-host interface and play a critical role in host response and microbiota homeostasis. Among these, peptidoglycan is the basic glycan polymer offering the cell rigidity and a basis on which many other glycoconjugates are anchored. To directly study peptidoglycan in gut commensals and obtain the molecular insight required to understand their functional activities we need effective techniques like chemical probes to label peptidoglycan in live bacteria. Here we report a chemically guided approach to study peptidoglycan in a key mucin-degrading gut microbiota member of the Verrucomicrobia phylum, Akkermansia muciniphila. Two novel non-toxic tetrazine click-compatible peptidoglycan probes with either a cyclopropene or isonitrile handle allowed for the detection and imaging of peptidoglycan synthesis in this intestinal species.

Enhancing Conventional PCR for Detection of Erwinia amylovora

Polymerase chain reaction (PCR) methods, including conventional PCR (cPCR) and quantitative real-time PCR (qRT-PCR), with both plasmid- and chromosome-targeting primers, are currently the most reliable methods for detecting <i>Erwinia amylovora</i> due to their high sensitivity and specificity. Despite qRT-PCR’s quantitative advantage, cPCR remains an attractive method to detect this bacterium in initial screenings of suspected host plants, as it is cost-effective and does not require skilled personnel in well-equipped laboratories. This study aimed to significantly improve cPCR robustness via application of bovine serum albumin (BSA) as a PCR facilitator, with a modified EaF/R primer pair, as previously reported. Experiments have shown that simple supplementation with BSA (10 mg/ml) enhances cPCR reactions using templates such as genomic DNA, bacterial cells, and infected symptomless host organs, including immature apple fruits and seedlings, with EaF/R primers. The cPCR method described in this study is simple, specific, and reliable, and can be applied in routine assays to diagnose fire blight.

Transition metal homoeostasis is key to metabolism and drug tolerance of Mycobacterium abscessus

AbstractAntimicrobial resistance (AMR) is one of the major challenges humans are facing this century. Understanding the mechanisms behind the rise of AMR is therefore crucial to tackling this global threat. The presence of transition metals is one of the growth-limiting factors for both environmental and pathogenic bacteria, and the mechanisms that bacteria use to adapt to and survive under transition metal toxicity resemble those correlated with the rise of AMR. A deeper understanding of transition metal toxicity and its potential as an antimicrobial agent will expand our knowledge of AMR and assist the development of therapeutic strategies. In this study, we investigate the antimicrobial effect of two transition metal ions, namely cobalt (Co2+) and nickel (Ni2+), on the non-tuberculous environmental mycobacterium and the opportunistic human pathogen Mycobacterium abscessus. The minimum inhibitory concentrations of Co2+ and Ni2+ on M. abscessus were first quantified and their impact on the bacterial intracellular metallome was investigated. A multi-omics strategy that combines transcriptomics, bioenergetics, metabolomics, and phenotypic assays was designed to further investigate the mechanisms behind the effects of transition metals. We show that transition metals induced growth defect and changes in transcriptome and carbon metabolism in M. abscessus, while the induction of the glyoxylate shunt and the WhiB7 regulon in response to metal stresses could be the key response that led to higher AMR levels. Meanwhile, transition metal treatment alters the bacterial response to clinically relevant antibiotics and enhances the uptake of clarithromycin into bacterial cells, leading to increased efficacy. This work provides insights into the tolerance mechanisms of M. abscessus to transition metal toxicity and demonstrates the possibility of using transition metals to adjuvant the efficacy of currently using antimicrobials against M. abscessus infections.

Evaluation of the Antibacterial Effects of the Punica granatum Peels Extracts Against some Pathogenic Bacteria: An In vivo and In vitro Study

Background: This study aimed to evaluate the antibacterial effects of Punica granatum extract on such pathogenic bacteria as Staphylococcus aureus and Escherichia coli. Materials and methods: The samples from 130 patients with skin infections in Baghdad, Iraq, aged between 15 and 60 over years were collected for this study. The study collected. Each isolate was positively identified using morphological, cultural, and biochemical assays as detailed in the reference. The P. granatum peels were air-dried and powdered. Then 25g were extracted using 500 mL of water and ethanol on Soxhlet equipment for 72 hours. The extracts were then cooled, filtered, and concentrated at 40oC to get the crude extract; it was kept at four degrees centigrade in dark vials until use. The extracts were tested for the presence of alkaloids, tannins, flavonoids, glycosides, as well as steroidal terpenes. The efficacy of antimicrobial effects was calculated using well-diffusion techniques on Muller Hinton Agar (MHA). The plates were injected with a standardized suspension of the test isolates against McFarland tube 0.5. Five wells, each measuring five millimeters in diameter, were evenly spaced out using a sterile standard core borer. The well bottoms were sealed with sterile molten nutritional agar to prevent the extract from leaking out from beneath the agar. The aqueous and ethanolic crude extracts dissolved in DMSO served as positive controls, while sterile water and 10% DMSO served as negative controls. Each extract was diluted to a final concentration of 50, 100, or 200mg/ml, and 25 ml was added to the appropriate well on the infected plate. The plates were then incubated for 24 hours at 37 degrees Celsius. A millimeter-calibrated ruler was used to measure the size of the resultant inhibitory zones. The zone of inhibition of the test microorganisms at that dose was calculated as the mean of three measurements. Results: Clinical isolates of E. coli and S. aureus were inhibited by pomegranate extracts at a concentration of 200mg/ml compared to other concentrations, and this extract concentration showed a non-significant difference with chloramphenicol (P<0.01). The study revealed that pomegranate peel extract significantly reduced E. coli levels in feces and increased survival rates in rats. On the first day, E. coli concentrations were much higher in the control group (G2) compared to the treatment group (G3). By day 6, all rats in the control group had died, while all rats in the treatment group survived. Pomegranate peel extract shows notable antibacterial properties, impacting bacterial membrane permeability and cell survival. The variation in extract composition affects its efficacy. Conclusion, Pomegranate peel extract significantly reduced E. coli levels and improved survival rates in rats. On day 6, all rats in the control group died, while all in the treatment group survived. The extract's antibacterial effects and impact on bacterial membranes highlight its potential as a therapeutic agent.

BPP43_05035 is a Brachyspira pilosicoli cell surface adhesin that weakens the integrity of the epithelial barrier during infection

ABSTRACT The anaerobic spirochete Brachyspira causes intestinal spirochetosis, characterized by the intimate attachment of bacterial cells to the colonic mucosa, potentially leading to symptoms such as diarrhea, abdominal pain, and weight loss. Despite the clinical significance of Brachyspira infections, the mechanism of the interaction between Brachyspira and the colon epithelium is not known. We characterized the molecular mechanism of the B. pilosicoli-epithelium interaction and its impact on the epithelial barrier during infection. Through a proteomics approach, we identified BPP43_05035 as a candidate B. pilosicoli surface protein that mediates bacterial attachment to cultured human colonic epithelial cells. The crystal structure of BPP43_05035 revealed a globular lipoprotein with a six-bladed beta-propeller domain. Blocking the native BPP43_05035 on B. pilosicoli, either with a specific antibody or via competitive inhibition, abrogated its binding to epithelial cells, which required cell surface-exposed N-glycans. Proximity labeling and interaction assays revealed that BPP43_05035 bound to tight junctions, thereby increasing the permeability of the epithelial monolayer. Extending our investigation to humans, we discovered a downregulation of tight junction and brush border genes in B. pilosicoli-infected patients carrying detectable levels of epithelium-bound BPP43_05035. Collectively, our findings identify BPP43_05035 as a B. pilosicoli adhesin that weakens the colonic epithelial barrier during infection.

MMO-induced batch and pilot-scale electro-oxidation treatment of municipal wastewater.

The present research aimed to explore the durability of MMO electrodes through electro-oxidation (EO) in purifying secondary treated actual sewage wastewater using batch and pilot-scale setups. The main aim is to inactivate bacteria in sewage treatment plants before they are released into the environment, thus contaminating water and soil. Process parameters such as current density (j), NaCl dose (n), and treatment time (t) were optimized using response surface methodology in a lab-scale EO reactor under batch conditions. The results showed that optimization of current density at 5.90mA/cm2 and NaCl concentration at 1.31g/L led to 93.90% of bacterial inactivation (Q1) within 8min of treatment and 0.48 kWh/m3 energy consumption (Q2). Biological analysis was conducted to validate bacterial cell destruction and count coliform bacteria in the EO-treated sewage wastewater. XRD, cyclic voltammetry studies, and FE-SEM/EDS analysis were done to confirm the MMO anode's durability and stability after 100 recycles. The study prioritized bacterial inactivation along with organic matter degradation. Besides that, a small pilot-scale study on the actual sewage wastewater with a volume of 10-50 L was done in batch mode under previously optimized conditions to analyze the efficacy of the MMO anodes in terms of bacterial inactivation.

Biofilm Eradication and Inhibition of Methicillin-Resistant Staphylococcus Clinical Isolates by Curcumin-Chitosan Magnetic Nanoparticles.

Biofilm-producing methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (MR-CoNS) pose clinical challenges in treating healthcare-associated infections. As alternative antimicrobial options are needed, in this study, we aimed to determine the effect of curcumin-chitosan magnetic nanoparticles (Cur-Chi-MNP) on the biofilms of staphylococcal clinical isolates. MRSA and CoNS clinical isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antimicrobial susceptibility testing was performed using the broth microdilutions. Nanoparticles were synthesized by the co-precipitation of magnetic nanoparticles (MNP) and encapsulated by the ionotropic gelation of curcumin (Cur) and chitosan (Chi). Biofilm inhibition and eradication by nanoparticles, with and without the addition of oxacillin (OXA), were assessed in Staphylococcus strains. Cur-Chi-MNP showed antimicrobial activity against planktonic cells of MRSA and MR-CoNS strains and inhibited MRSA biofilm. The addition of OXA to Cur-Chi-MNP increased the biofilm inhibition and eradication activity against all staphylococcal strains (P = 0.0007), and higher biofilm activity was observed in the early biofilm stages. Cur-Chi-MNP showed antimicrobial and biofilm inhibitory activities against S. aureus. Addition of OXA increased biofilm inhibition and eradication activity against all staphylococcal strains. A combination treatment of Cur-Chi-MNP and OXA could potentially be used to treat staphylococcal biofilm-associated infections in the early stages before the establishment of biofilm bacterial cells.

H2O2 Self‐Supplying CaO2/POM@MOF Bimodal Nanogeneration Materials for Photothermal and Chemodynamic Synergistic Antimicrobials

ABSTRACTThe emergence of bacterial resistance has a negative impact on the conventional antimicrobial treatments, and research into the development of the new antimicrobial materials is of great significance. Multimodal synergistic antimicrobial materials exert better antimicrobial effects compared with a single modality. In recent years, Polyoxometalate (POM) has shown great potential in the biomedical field due to its high catalytic activity and high photothermal conversion ability. However, owing to its small surface area, its applications have been greatly limited. Herein, we designed a H2O2 self‐supplied CDT and PTT bimodal nanogeneration material (i.e., CaO2/POM@MOF) possessing a larger surface area for the treatment of the bacterial infections, in which CaO2 could release O2 and H2O2 in the weakly acidic microenvironment of bacterial infection and the dual catalytic site of POM@MOF could enhance the CDT reaction to generate ROS, resulting in the bacterial oxidative stress and the leakage of the bacterial contents, and the exposure to the NIR light generates localized high temperature that cause the rupture of bacterial cell membranes and the denaturation of their proteins. Meanwhile, the superior stability of POM@MOF can release fewer metal ions to improve its biocompatibility. The in vitro antimicrobial experiments demonstrated that CaO2/POM@MOF possessed the combined CDT and PTT effect and exhibited excellent antimicrobial efficacy. This work presents a promising strategy to combat the bacterial infections.

Electrosynthesis of Anisotropic Biogenic Silver Nanoparticles as A Promising Antibacterial Agent Using Stachytarpheta Jamaicensis Leaf Extract

Antibiotic-resistant bacteria provide a great opportunity to use silver nanoparticles (AgNPs) as potential antibiotic replacements. This work utilized Stachytarpheta jamaicensis leaf extract (SJLE)-mediated electrosynthesis of biogenic AgNPs. By using two silver rods and SJLE as the electrolysis medium, biogenic AgNP is produced through electrosynthesis. The properties of the formed AgNPs and SJLE phytochemical composition were examined. The disc diffusion method was utilized to evaluate AgNPs' antibacterial efficacy against Escherichia coli and Staphylococcus aureus. The high amount of phenolics, flavonoids, and tannins in SLJE provides biomolecules rich in -OH and carbonyl groups, allowing SLJE to have antimicrobial effects as well as act as a capping agent and bioreductor during electrosynthesis. The presence of functional groups from various phytochemicals leads to the formation of anisotropic AgNP crystals with a size of 38.22 ± 13.06 nm and high purity (95.75 ± 0.43%). Antibacterial activity tests against E. coli and S. aureus show that anisotropic biogenic AgNPs outperformed spherical AgNPs, probably due to the angular AgNPs' ease of penetration into bacterial cell walls. The characteristics of the AgNPs developed induced outstanding antibacterial efficacy against E. coli and S. aureus. Thus, SLJE-based electrosynthesis provides a synergistic synthetic design of AgNPs as antibacterial agents with several potential long-term advantages, including high purity, fast synthesis, low cost, absence of hazardous ingredients, and simplicity in scaling up.

NOD2-mediated dual negative regulation of inflammatory responses triggered by TLRs in the gastrointestinal tract.

Loss-of-function mutations in nucleotide-binding oligomerization domain 2 (NOD2) constitute the primary risk factors for Crohn's disease. NOD2 is an intracellular sensor for muramyl dipeptide (MDP), a small molecule derived from the peptidoglycan layer of bacterial cell wall. Although NOD2 is involved in host immune responses, much attention has been paid to the involvement of NOD2 in the maintenance of intestinal homeostasis. Despite the fact that the proinflammatory cytokine and chemokine responses induced by NOD2 activation alone are weaker than those induced by toll-like receptors (TLRs), NOD2 plays a crucial role in host defense against invading pathogens and in the regulation of immune responses. Recent studies have highlighted the importance of negative regulatory functions of NOD2 in TLRs-mediated proinflammatory cytokine responses. MDP-mediated activation of NOD2 induces interferon regulatory factor 4 (IRF4) expression, thereby suppressing nuclear factor-κB-dependent colitogenic cytokine responses through the inhibition of Lys(K)63-linked polyubiquitination on receptor-interacting serine/threonine protein kinase 2. MDP-mediated activation of NOD2 also downregulates TLR9-induced type I IFN responses by inhibiting the K63-linked polyubiquitination of TNF receptor-associated factor 3 via deubiquitinating enzyme A (DUBA) expression. Thus, NOD2 exerts dual negative regulation of TLRs-mediated proinflammatory cytokine and type I IFN responses by inducing the expression of IRF4 and DUBA, respectively. In this review, we summarize the molecular mechanisms whereby NOD2 activation suppresses TLRs-mediated proinflammatory and type I IFN responses. In addition, we discuss the clinical relevance of the NOD2-mediated negative regulation of TLRs in inflammatory bowel disease.

Effect of The Temperature on The Size of Inhibition Zone of the Clindamycin, Levofloxacin, Tetracycline, and Trimethoprim Activity Against Staphylococcus aureus ATCC 25923

Antibiotic sensitivity should be tested. In the sensitivity test, there are technical factors that influence the formation of the inhibition zone diameter. Based on several research one of the technical factors that affect the diameter of the inhibition in the disc diffusion method is the temperature incubation of the media, this must be examined so that it can be controlled to ensure the validity of the sensitivity test results. This study aims to determine the mean, difference, and analyze the diameter of the inhibition zone of the antibiotics namely Clindamycin, Levofloxacin, Tetracycline, and Trimethoprim against Staphylococcus aureus on Mueller-Hinton agar media with incubation temperatures of 33°C, 34°C, 35°C, 36°C and 37°C for 18 hours. This research is observational, with a cross-sectional design. The data used are primary data with 100 data on the diameter of the antibiotic inhibition zone, obtained by measuring the diameter of the inhibition zone with different incubation temperatures. The selection of antibiotics is based on the mechanism of action of antibiotics inhibiting bacteria namely, the cell wall or membranes that surrounds the bacterial cell; the machineries that make the nucleic acids DNA and RNA and the machinery that produce proteins (the ribosome and associated proteins) with a range of inhibition zones based on Internal Quality Control CLSI. The data will be processed univariately and the Repeated Measure statistical test to determine the significance of the difference in the diameter of the formed inhibition zone using the ANOVA test. The results of the measurement of the inhibition zone diameter on the incubation temperature variation showed a significant difference with p-value 0.000 for Levofloxacin, Tetracycline and Trimethoprim, while for p-value Clindamycin is 0.010. Levofloxacin, Tetracycline, and Trimethoprim antibiotics, the higher the incubation temperature, the average diameter of the inhibition zone is smaller, while for Clindamycin the higher the incubation temperature, the higher the average diameter of the inhibition zone is the same. There is an effect of incubation temperature volume on the diameter of the antibiotic inhibition zone in the disc diffusion method antibiotic sensitivity test. The research indicates that incubation temperature affects the diameter of the antibiotic inhibition zone in disc diffusion tests, underscoring the need for standardized and precise testing conditions to ensure accurate and reliable antibiotic sensitivity results.

Analysis of Bacterial Characteristics Using the Electrical Impedance Spectroscopy Method

Microorganisms have various shapes, structures, and characteristics. This study uses the method of electrical impedance spectroscopy aimed at identifying and comparing the characteristics of Escherichia Coli, Salmonella Typhi, and Staphylococcus Aureus. Measurements from 1 Hz to 100,000 Hz show that Salmonella Typhi has the highest impedance value at low frequencies. In contrast, Escherichia Coli impedance decreases consistently, and Staphylococcus Aureus decreases sharply after 10 Hz. Significant changes are observed in the mid-frequency range of 100 Hz to 1000 Hz, with Salmonella Typhi showing the highest impedance values at 100 Hz compared to Staphylococcus Aureus and Escherichia Coli. At 100 Hz, Salmonella Typhi has the highest impedance value with a mass of 0,06 grams at approximately 39.000 Ohms, 0,08 grams at 35.000 Ohm, and 10 grams at 34.000 Ohm. This is followed by Staphylococcus Aureus, with a mass 0f 0,06 grams having an impedance value of 23.000 Ohms, 0,08 grams having a high impedance value of 31.000 Ohm, and 0,10 grams having an impedance value of 15.000 Ohm. Escherichia Coli, with a mass of 0.06 grams, has an impedance value of 9.000 Ohms, 0,08 grams with an impedance value of 5.000 Ohms, and 0,10 grams has an impedance value of 5.000 Ohms. Electrical Impedance Spectroscopy is effective for identifying and comparing Escherichia coli, Staphylococcus aureu, and Salmonella typhi as the intrinsic characteristics of bacterial cells more influence impedance than bacterial mass.

A membrane localized RTX-like protein mediates physiochemical properties of the Pantoea stewartii subsp. stewartii cell envelope that impact surface adhesion, cell surface hydrophobicity and plant colonization

Pantoea stewartii subsp. stewartii (Pnss), is the bacterial causal agent of Stewart’s wilt of sweet corn. Disease symptoms include systemic wilting and foliar, water-soaked lesions. A Repeat-in-toxin (RTX)-like protein, RTX2, causes cell leakage and collapse in the leaf apoplast of susceptible corn varieties and is a primary mediator of water-soaked lesion formation in the P. stewartii-sweet corn pathosystem. RTX toxins comprise a large family of proteins, which are widely distributed among Gram-negative bacteria. These proteins are generally categorized as cellulolysins, but the Biofilm-Associated Proteins (Bap) subfamily of RTX toxins are implicated in surface adhesion and other biofilm behaviors. The Pnss RTX2 is most phylogenetically related to other Bap proteins suggesting that Pnss RTX2 plays a dual role in adhesion to host surfaces in addition to mediating the host cell lysis that leads to water-soaked lesion formation. Here we demonstrated that RTX2 localizes to the bacterial cell envelope and influences physiochemical properties of the bacterial cell envelope that impact bacterial cell length, cell envelope integrity and overall cellular hydrophobicity. Interestingly, the role of RTX2 as an adhesin was only evident in absence of exopolysaccharide (EPS) production suggesting that RTX2 plays a role as an adhesin early in biofilm development before EPS production is fully induced. However, deletion of rtx2 severely impacted Pnss’ colonization of the xylem suggesting that the dual role of RTX2 as a cytolysin and adhesin is a mechanism that links the apoplastic water-soaked lesion phase of infection to the wilting phase of the infection in the xylem.

Proteome Changes Induced by Iprodione Exposure in the Pesticide-Tolerant Pseudomonas sp. C9 Strain Isolated from a Biopurification System

Iprodione is a pesticide that belongs to the dicarboximide fungicide family. This pesticide was designed to combat various agronomical pests; however, its use has been restricted due to its environmental toxicity and risks to human health. In this study, we explored the proteomic changes in the Pseudomonas sp. C9 strain when exposed to iprodione, to gain insights into the affected metabolic pathways and enzymes involved in iprodione tolerance and biodegradation processes. As a result, we identified 1472 differentially expressed proteins in response to iprodione exposure, with 978 proteins showing significant variations. We observed that the C9 strain upregulated the expression of efflux pumps, enhancing its tolerance to iprodione and other harmful compounds. Peptidoglycan-binding proteins LysM, glutamine amidotransferase, and protein Ddl were similarly upregulated, indicating their potential role in altering and preserving bacterial cell wall structure, thereby enhancing tolerance. We also observed the presence of hydrolases and amidohydrolases, essential enzymes for iprodione biodegradation. Furthermore, the exclusive identification of ABC transporters and multidrug efflux complexes among proteins present only during iprodione exposure suggests potential counteraction against the inhibitory effects of iprodione on downregulated proteins. These findings provide new insights into iprodione tolerance and biodegradation by the Pseudomonas sp. C9 strain.

Mechanism of pyrite depression by marine Fe(II)-oxidizing bacteria in seawater flotation

Seawater flotation is a promising technique to reduce environmental and economic loads in mineral processing. This study attempted to depress pyrite, a common gangue sulfide mineral, using two marine iron (Fe) oxidizing bacteria (MFeOB), Thalassospira sp. TF-1 and Mariprofundus sp. E-4, in seawater flotation without pH control; the MFeOB could contribute to hydrophilization of the pyrite surface by oxidation and/or adhesion of bacterial cells. Pyrite or chalcopyrite samples were preconditioned in seawater containing MFeOB for different times (15 min or 30 min). As a result of flotation experiments, the recovery of pyrite preconditioned without MFeOB (i.e., control sample) decreased to 64.2 % after 30 min reaction. The same recovery was observed when pyrite was preconditioned with Thalassospira sp. TF-1, whereas the recovery was successfully decreased to 20.2 % after preconditioning with Mariprofundus sp. E-4 for 30 min. X-ray photoelectron spectroscopy analysis of preconditioned pyrite samples showed no significant difference of Fe-oxidizing compounds between with and without MFeOB reaction, suggesting that the formation of hydrophilic substances such as Fe(OH)3 derived from pyrite oxidation by MFeOB is unlikely to be the main reason for the pyrite depression by Mariprofundus sp. E-4. The adhesion experiment revealed that MFeOB cells could cover the pyrite surface but not the chalcopyrite surface, showing that the hydrophilicity of Mariprofundus sp. E-4 cell caused the pyrite depression. This result suggests that the hydrophilic/hydrophobic properties of bacterial cells are a significant determining factor in pyrite recovery in seawater flotation in the case of MFeOB.

Synergistic Effect of Metronidazole and Chlorhexidine against Porphyromonas gingivalis Growth: An In Vitro Study.

Aim: To evaluate the potential synergistic activity of metronidazole (MTZ) and chlorhexidine (CHX) against Porphyromonas. gingivalis (P. gingivalis) growth. Methods: Antimicrobial susceptibility tests of P. gingivalis to MTZ and CHX were performed on in vitro serial 2-fold dilutions of MTZ (from 1 mg/mL to 0.015 mg/mL) and CHX (from 1 mg/mL to 0.03 mg/mL) in thioglycollate medium broth in a 96-well plate. The turbidity of each sample was analyzed by absorbance spectrophotometry at 450 nm wavelengths by using an enzyme-linked immunosorbent assay (ELISA) reader. The MIC50 (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) were assessed. To investigate the potential synergism between MTZ and CHX, bacterial cells were treated with MTZ or CHX, as described above, either alone or in combination. Results: The MIC50 of MTZ was 0.03 mg/mL while that of CHX ranged from 0.12 to 0.06 mg/mL. MTZ and CHX exerted a significant inhibitory effect on P. gingivalis growth in a dose-dependent manner. MTZ at a low and ineffective concentration of 0.015 mg/mL, associated with a suboptimal concentration of CHX (0.03 mg/mL), exhibited a significant synergistic inhibitory effect on bacterial growth (50% inhibition vs. control) (p < 0.001), and the effect was more remarkable with 0.06 mg/mL CHX (75% inhibition vs. control). Conclusions: CHX and MTZ showed a significant synergistic effect against P. gingivalis growth. A non-effective concentration of MTZ (0.015 mg/mL) combined with suboptimal concentrations of CHX (0.03 mg/mL and 0.06 mg/mL) were related to a 50% growth in the inhibition and 99.99% death of P. gingivalis, respectively. The applicability of the clinical use of these concentrations should be tested in randomized controlled trials.

Preparation of Zinc Oxide Nanoparticles and the Evaluation of their Antibacterial Effects.

Nosocomial bacterial infections have become increasingly challenging due to their inherent resistance to antibiotics. The emergence of multidrug-resistant bacterial strains in hospitals has been attributed to the extensive and varied use of antibiotics, further exacerbating the problem of antibiotic resistance. Metal nanomaterials have been widely studied as an alternative solution for eradicating antibiotic-resistant bacterial cells. Metallic nanoparticles attack bacterial cells through various mechanisms, such as the release of antibacterial ions, generation of reactive oxygen species, or physical disruption, against which bacteria cannot develop resistance. Among the actively researched antimicrobial metal nanoparticles, zinc oxide nanoparticles, which are FDA-approved, are known for their biocompatibility and antibacterial properties. In this study, we focused on successfully developing a precipitation method for synthesizing zinc oxide nanoparticles, analyzing the properties of these nanoparticles, and conducting antimicrobial tests. Zinc oxide nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), ultraviolet/visible spectroscopy, and X-ray diffraction (XRD). Antibacterial tests were conducted using the broth microdilution test with the multidrug-resistant strains of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. This study demonstrated the potential of zinc oxide nanoparticles in inhibiting the proliferation of antibiotic-resistant bacteria.

Absence of synergistic effects between microplastics and copper ions on the spread of antibiotic resistance genes within aquatic bacteria at the community level

Microplastics and copper ions (Cu2+) are favorable in accelerating the propagation of antibiotic resistance genes (ARGs) in the plastisphere, however, their combined effects on the ARG spread within the bacterial community of the natural environment were less understood. The influence of microplastic types and Cu2+ concentrations on the horizontal gene transfer (HGT) of ARGs mediated by RP4 plasmid within natural bacterial communities in aquatic environments was investigated. Both biodegradable polybutylene succinate (PBS) and non-biodegradable polyvinyl chloride (PVC) microplastics significantly enhanced the transfer of ARGs, with PBS showing a significant higher effect compared to PVC. Cu2+ also increased transconjugation rates at environmentally relevant concentrations (5 μg L−1), but higher levels (50 μg L−1) lead to decreased rates due to severe bacterial cell membrane damage. The transconjugation rates in the presence of both microplastics and Cu2+ were lower than the sum of their individual effects, indicating no synergistic effects between them on transconjugation. Proteobacteria dominated the composition of transconjugates for all the treatment. Transmission electron microscope images and reactive oxygen species production in bacterial cells indicated that the increased contact frequency due to extracellular polymeric substances, combined with enhanced membrane permeability induced by microplastics and Cu2+, accounted for the increasing transconjugation rates. The study provides valuable insight into the potential effects of microplastics and heavy metals on the spread of ARGs from donors to bacterial communities in natural environments.

A host-adapted auxotrophic gut symbiont induces mucosal immunodeficiency.

Harnessing the microbiome to benefit human health requires an initial step in determining the identity and function of causative microorganisms that affect specific host physiological functions. We show a functional screen of the bacterial microbiota from mice with low intestinal immunoglobulin A (IgA) levels; we identified a Gram-negative bacterium, proposed as Tomasiella immunophila, that induces and degrades IgA in the mouse intestine. Mice harboring T. immunophila are susceptible to infections and show poor mucosal repair. T. immunophila is auxotrophic for the bacterial cell wall amino sugar N-acetylmuramic acid. It delivers immunoglobulin-degrading proteases into outer membrane vesicles that preferentially degrade rodent antibodies with kappa but not lambda light chains. This work indicates a role for symbionts in immunodeficiency, which might be applicable to human disease.