Iron Uptake Research Articles

Slightly acidic electrolyzed water inhibits inflammation induced by membrane vesicles of Staphylococcus aureus.

Staphylococcus aureus grows in the skin of patients with atopic dermatitis and the associated symptoms are induced by membrane vesicles (MVs). This study explored the effects of slightly acidic electrolyzed water (SAEW) on the expression of virulence factors of S. aureus and MV-induced inflammation to uncover the potential of SAEW as a new treatment method for atopic dermatitis. Expression levels of genes related to virulence factors in S. aureus was assessed and S. aureus-derived MVs were characterized. Moreover, expression level of MV-induced Type I allergic reaction-related genes in RBL2H3 cells was also assessed. Significantly decreased staphylococcal enterotoxin A production and decreased virulence factor-related gene expression were observed after culturing S. aureus in broth supplemented with SAEW at ratios of 1, 2, and 5 per broth. MVs prepared by culturing S. aureus in SAEW-supplemented broth exhibited altered particle size and markedly reduced staphylococcal enterotoxin A content under all addition conditions; moreover, those obtained at a ratio of 1:5 (broth:SAEW) exhibited a reduction in the expression of several proteins associated with hemolytic activity and free iron uptake. The MVs prepared in SAEW-supplemented broth also exhibited remarkably reduced allergy-related gene expression levels in rat cell lines derived from basophilic leukemia-2H3 cells. Overall, SAEW is expected to suppress atopic dermatitis symptoms through the alteration of the properties of S. aureus-derived MVs.

A Water-Soluble Chitosan Derivative for the Release of Bioactive Deferoxamine.

Deferoxamine (DFO) is a water-soluble iron chelator used pharmacologically for the management of patients with transfusional iron overload. However, DFO is not cell-permeable and has a short plasma half-life, which necessitates lengthy parenteral administration with an infusion pump. We previously reported the synthesis of chitosan (CS) nanoparticles for sustained slow release of DFO. In the present study, we developed solid dispersions and nanoparticles of a carboxymethyl water-soluble chitosan derivative (CMCS) for improved DFO encapsulation and release. CS dispersions and nanoparticles with DFO have been prepared by ironical gelation using sodium triphosphate (TPP) and were examined for comparison purposes. The successful presence of DFO in CMCS polymeric dispersions and nanoparticles was confirmed through FTIR measurements. Furthermore, the formation of CMCS nanoparticles led to inclusion of DFO in an amorphous state, while dispersion of DFO in the polymeric matrix led to a decrease in its crystallinity according to X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results. An in vitro release assay indicated sustained release of DFO from CS and CMCS nanoparticles over 48 h and 24 h, respectively. Application of CMCS-DFO dispersions to murine RAW 264.7 macrophages or human HeLa cervical carcinoma cells triggered cellular responses to iron deficiency. These were exemplified in the induction of the mRNA encoding transferrin receptor 1, the major iron uptake protein, and the suppression of ferritin, the iron storage protein. Our data indicate that CMCS-DFO nanoparticles release bioactive DFO that causes effective iron chelation in cultured cells.

Effects of lime supply on the uptake of potassium and iron released from phlogopite by alfalfa

Understanding the influence of carbonates on nutrient release from minerals and their availability to plants is necessary for the management of calcareous soils. This study was conducted to investigate the effects of various levels of lime on the release of potassium (K) and iron (Fe) from the phlogopite mineral in the rhizosphere and their uptake by alfalfa. The experiment was conducted using a completely randomized design with a factorial arrangement. Alfalfa was grown in media containing a mixture of quartz sand, phlogopite, and different levels of lime (0, 20, 50, 120, and 250 g kg−1) under four types of nutrient solution (complete, Fe-free, K-free, and Fe and K free) with three replicates for six months. Alfalfa shoots and roots were harvested and their K and Fe concentrations were measured. The results showed that the biomass of both shoots and roots was significantly affected by lime. The presence of lime in the rhizosphere resulted in an increase in available Ca, thereby reducing the absorption of both K and Fe. The presence of lime was also found to change the K/Ca balance in the growth media. This appears to be the reason for the increased shoot K concentration in plants grown in the media containing less carbonates. It seems that at high concentrations in the soil solution, Ca competes greatly with Fe, reducing its availability to plants. In general, the rates of K and Fe release from phlogopite were adversely influenced by the level of carbonates in the root zone.

Effect of foliar spray of zinc sulphate and iron sulphate on yield, quality and nutrient uptake of chickpea (Cicer arietinum L.) in Vertisols

A field experiment was conducted at farmer’s field in Yattingudda village (Dharwad district) to study theBiofortification of zinc sulphate and iron sulphate though foliar spray on yield, quality and nutrient uptake of chickpea(Cicer arietinum L.) in Vertisol during rabi 2020. The experiment was laid out in Randomized Complete Block design(RCBD) with nine treatments and three replications combination with different levels of zinc sulphate and iron sulphate.The results revealed that, among the different treatments, foliar spray of ZnSO4. 7H2O and FeSO4.7H2O @ 0.5% at the timeof pre flowering, flowering and pod setting along with recommended package of practices recorded the significantly highernumber of pods plant-1 (37.62), pod weight per plant (11.89 g plant-1), 100 seed weight (23.96g), seed yield (18.21 q ha-1)and haulm yield (25.14 q ha-1). This treatment also recorded significantly higher crude protein content (24.12 per cent), zinccontent (41.12 mg kg-1), iron content (134.25 mg kg-1) and also higher uptake of nitrogen (90.39 kg ha-1), phosphorus(11.03 kg ha-1), potassium (48.89 kg ha-1), sulphur (11.94kg ha-1) zinc (146.38 g ha-1) and iron (449.16 g ha-1).

Spatial IMA1 regulation restricts root iron acquisition on MAMP perception.

Iron is critical during host-microorganism interactions1-4. Restriction of available iron by the host during infection is an important defence strategy, described as nutritional immunity5. However, this poses a conundrum for externally facing, absorptive tissues such as the gut epithelium or the plant root epidermis that generate environments that favour iron bioavailability. For example, plant roots acquire iron mostly from the soil and, when iron deficient, increase iron availability through mechanisms that include rhizosphere acidification and secretion of iron chelators6-9. Yet, the elevated iron bioavailability would also be beneficial for the growth of bacteria that threaten plant health. Here we report that microorganism-associated molecular patterns such as flagellin lead to suppression of root iron acquisition through a localized degradation of the systemic iron-deficiency signalling peptide Iron Man 1 (IMA1) in Arabidopsis thaliana. This response is also elicited when bacteria enter root tissues, but not when they dwell on the outer root surface. IMA1 itself has a role in modulating immunity in root and shoot, affecting the levels of root colonization and the resistance to a bacterial foliar pathogen. Our findings reveal an adaptive molecular mechanism of nutritional immunity that affects iron bioavailability and uptake, as well as immune responses.

Cryptochrome PtCPF1 regulates high temperature acclimation of marine diatoms through coordination of iron and phosphorus uptake.

Increasing ocean temperatures threaten the productivity and species composition of marine diatoms. High temperature response and regulation are important for the acclimation of marine diatoms to such environments. However, the molecular mechanisms behind their acclimation to high temperature are still largely unknown. In this study, the abundance of PtCPF1 homologs (a member of the cryptochrome-photolyase family in the model diatom Phaeodactylum tricornutum) transcripts in marine phytoplankton is shown to increase with rising temperature based on Tara Oceans datasets. Moreover, the expression of PtCPF1 in P. tricornutum at high temperature (26 °C) was much higher than that at optimum temperature (20 °C). Deletion of PtCPF1 in P. tricornutum disrupted the expression of genes encoding two phytotransferrins (ISIP2A and ISIP1) and two Na+/P co-transporters (PHATRDRAFT_47667 and PHATRDRAFT_40433) at 26 °C. This further impacted the uptake of Fe and P, and eventually caused the arrest of cell division. Gene expression, Fe and P uptake, and cell division were restored by rescue with the native PtCPF1 gene. Furthermore, PtCPF1 interacts with two putative transcription factors (BolA and TF IIA) that potentially regulate the expression of genes encoding phytotransferrins and Na+/P co-transporters. To the best of our knowledge, this is the first study to reveal PtCPF1 as an essential regulator in the acclimation of marine diatoms to high temperature through the coordination of Fe and P uptake. Therefore, these findings help elucidate how marine diatoms acclimate to high temperature.

Characterization of Escherichia coli Isolated from Sows Presenting Purulent Vulvar Discharge.

Purulent vulvar discharge is a clinical sign of genitourinary tract infections, which are a significant concern in swine facilities, leading to sow culling and mortality. Escherichia coli is one of the main agents involved in these diseases. This study aimed to characterize the virulence and antimicrobial resistance profiles as well as the phylotype of Escherichia coli strains isolated from sows with purulent vulvar discharge. The results showed that at least 2 of the 29 tested virulence genes related to extraintestinal pathogenic E. coli were present in all strains tested. The most frequent gene was iutA, present in all strains, followed by the genes iucD, csgA, iss2, and irp2. Associations between iron uptake genes, genes related to adhesion, attachment, and serum resistance, as well as genes related to toxin release and bacteriocin, were frequent. The most prevalent phylotype was B1 (40.0%), followed by A (18.5%), D (11.9%), C (9.6%), B2 (7.4%), E (4.4%), F (1.5%), and Clade I (0.7%), with B2 being related to highly virulent traits. The strains presented elevated resistance to antimicrobials such as ciprofloxacin, streptomycin, cephalexin, florfenicol, and ampicillin. More than 90% of the strains were identified as multidrug-resistant, indicating the selection that is induced by the high use of antimicrobials in swine farming.

Adsorption of particulate matter and uptake of metal and non-metal elements from PM in leaves of Pinus densiflora and Quercus acutissima: a comparative study

Trees can serve as effective biofilters of Particulate matter (PM) pollution, making them valuable for managing air pollution and promoting public health. Leaves of trees can reduce PM through absorption, adsorption, and fallout mechanisms, which are influenced by species-specific characteristics and environmental factors. Although several studies have explored the impact of various leaf characteristics on their ability to adsorb PM from field conditions, few have been conducted in controlled chambers to analyze the adsorption of PM on leaf surfaces and the uptake of metal and non-metal elements from PM on leaves. To fill these knowledge gaps, this study investigated the PM adsorption and leaf characteristics of two different tree species, Pinus densiflora (an evergreen coniferous species) and Quercus acutissima (a deciduous broad-leaved species) under controlled conditions in a PM exposure chamber with a target concentration of 300 μg m−3. The main aim of this study was to measure and compare the rate of PM component (metal and non-metal elements) uptake in two species and investigate the leaf characteristics that contribute to PM adsorption. We investigated the relationship between PM adsorption and physiolog, micro-morphology, and chemical properties of the leaf surface in two species. This study used a Pearson’s correlation analysis and a principal component analysis (PCA) to evaluate correlation between PM adsorption and leaf characteristics and uptake of metal/non-metal elements in PM on leaves. This result showed that leaf characteristics such as stomatal size, leaf roughness, and wax content played a crucial role in PM10 adsorption, while physiological factors like transpiration and leaf boundary layer conductance were identified as important determinants of PM2.5 adsorption on plant leaves. It also observed significant variations in the uptake of aluminum, iron, magnesium, phosphorus, and sulfur. This study not only advances our understanding of the mechanisms behind PM adsorption by tree leaves but also underscores the importance of selecting appropriate tree species based on their leaf characteristics for urban forestry and green infrastructure projects. The ability to strategically use tree species for PM pollution mitigation highlights a practical approach to enhancing environmental sustainability and public health.

HY5: a key regulator for light-mediated nutrient uptake and utilization by plants.

ELONGATED HYPOCOTYL 5 (HY5), a bZIP-type transcription factor, is a master regulator of light-mediated responses. ELONGATED HYPOCOTYL 5 binds to the promoter of c. 3000 genes, thereby regulating various physiological and biological processes, including photomorphogenesis, flavonoid biosynthesis, root development, response to abiotic stress and nutrient homeostasis. In recent decades, it has become clear that light signaling plays a crucial role in promoting nutrient uptake and assimilation. Recent studies have revealed the molecular mechanisms underlying such encouraging effects and the crucial function of the transcription factor HY5, whose activity is regulated by many photoreceptors. The discovery that HY5 directly activates the expression of genes involved in nutrient uptake and utilization, including several nitrogen, iron, sulphur, phosphorus and copper uptake and assimilation-related genes, enhances our understanding of how light signaling regulates uptake and utilisation of multiple nutrients in plants. Here, we review recent advances in the role of HY5 in light-dependent nutrient uptake and utilization.

Cancer Cell Targeting Via Selective Transferrin Receptor Labeling Using Protein-Derived Carbon Dots.

Carbon dot (CD) nanoparticles offer tremendous advantages as fluorescent probes in bioimaging and biosensing; however, they lack specific affinity for biomolecules, limiting their practical applications in selective targeting. Nanoparticles with intrinsic affinity for a target have applications in imaging, cytometry, therapeutics, etc. Toward that end, we report the transferrin receptor (CD71) targeting CDs, synthesized for the first time. The formation of these particles is truly groundbreaking, as direct tuning of nanoparticle affinity was achieved by simple and careful precursor selection of a protein, which has the targeting characteristic of interest. We hypothesized that the retention of the original protein's peptides on the nanoparticle surface provides the CDs with some of the function of the precursor protein, enabling selective binding to the protein's receptor. This was confirmed with FTIR (Fourier transform infrared) data and subsequent affinity-based cell assays. These transferrin (Tf)-derived CDs have been shown to possess an affinity for CD71, a cancer biomarker that is ubiquitously expressed in nearly every cancer cell line due to its central role mediating the uptake of cellular iron. The CDs were tested using the human leukemia cell line HL60 and demonstrated the selective targeting of CD71 and specific triggering of transferrin-mediated endocytosis via clathrin-coated pits. The particle characterization results reflect a carbon-based nanoparticle with bright violet fluorescence and 7.9% quantum yield in aqueous solution. These unpresented CDs proved to retain the functional properties of the precursor protein. Indicating that this process can be repeated for other disease biomarkers for applications ranging from biosensing and diagnostic bioimaging to targeted therapeutics.

PQS and pyochelin in Pseudomonas aeruginosa share inner membrane transporters to mediate iron uptake.

Bacteria absorb different forms of iron through various channels to meet their needs. Our previous studies have shown that TseF, a type VI secretion system effector for Fe uptake, facilitates the delivery of outer membrane vesicle-associated Pseudomonas quinolone signal (PQS)-Fe3+ to bacterial cells by a process involving the Fe(III) pyochelin receptor FptA and the porin OprF. However, the form in which the PQS-Fe3+ complex enters the periplasm and how it is moved into the cytoplasm remain unclear. Here, we first demonstrate that the PQS-Fe3+ complex enters the cell directly through FptA or OprF. Next, we show that inner membrane transporters such as FptX, PchHI, and FepBCDG are not only necessary for Pseudomonas aeruginosa to absorb PQS-Fe3+ and pyochelin (PCH)-Fe3+ but are also necessary for the virulence of P. aeruginosa toward Galleria mellonella larvae. Furthermore, we suggest that the function of PQS-Fe3+ (but not PQS)-mediated quorum-sensing regulation is dependent on FptX, PchHI, and FepBCDG. Additionally, the findings indicate that unlike FptX, neither FepBCDG nor PchHI play roles in the autoregulatory loop involving PchR, but further deletion of fepBCDG and pchHI can reverse the inactive PchR phenotype caused by fptX deletion and reactivate the expression of the PCH pathway genes under iron-limited conditions. Finally, this work identifies the interaction between FptX, PchHI, and FepBCDG, indicating that a larger complex could be formed to mediate the uptake of PQS-Fe3+ and PCH-Fe3+. These results pave the way for a better understanding of the PQS and PCH iron absorption pathways and provide future directions for research on tackling P. aeruginosa infections.IMPORTANCEPseudomonas aeruginosa has evolved a number of strategies to acquire the iron it needs from its host, with the most common being the synthesis, secretion, and uptake of siderophores such as pyoverdine, pyochelin, and the quorum-sensing signaling molecule Pseudomonas quinolone signal (PQS). However, despite intensive studies of the siderophore uptake pathways of P. aeruginosa, our understanding of how siderophores transport iron across the inner membrane into the cytoplasm is still incomplete. Herein, we reveal that PQS and pyochelin in P. aeruginosa share inner membrane transporters such as FptX, PchHI, and FepBCDG to mediate iron uptake. Meanwhile, PQS and pyochelin-mediated signaling operate to a large extent via these inner membrane transporters. Our study revealed the existence of shared uptake pathways between PQS and pyochelin, which could lead us to reexamine the role of these two molecules in the iron uptake and virulence of P. aeruginosa.

Identification and characterization of yellow stripe-like genes in maize suggest their roles in the uptake and transport of zinc and iron

BackgroundYellow Stripe-Like (YSL) proteins are involved in the uptake and transport of metal ions. They play important roles in maintaining the zinc and iron homeostasis in Arabidopsis, rice (Oryza sativa), and barley (Hordeum vulgare). However, proteins in this family have not been fully identified and comprehensively analyzed in maize (Zea mays L.).ResultsIn this study, we identified 19 ZmYSLs in the maize genome and analyzed their structural features. The results of a phylogenetic analysis showed that ZmYSLs are homologous to YSLs of Arabidopsis and rice, and these proteins are divided into four independent branches. Although their exons and introns have structural differences, the motif structure is relatively conserved. Analysis of the cis-regulatory elements in the promoters indicated that ZmYSLs might play a role in response to hypoxia and light. The results of RNA sequencing and quantitative real-time PCR analysis revealed that ZmYSLs are expressed in various tissues and respond differently to zinc and iron deficiency. The subcellular localization of ZmYSLs in the protoplast of maize mesophyll cells showed that they may function in the membrane system.ConclusionsThis study provided important information for the further functional analysis of ZmYSL, especially in the spatio-temporal expression and adaptation to nutrient deficiency stress. Our findings provided important genes resources for the maize biofortification.

Tropical postbiotics alleviate the disorders in the gut microbiota and kidney damage induced by ochratoxin A exposure.

Ochratoxin A (OTA), commonly found in various foods, significantly impacts the health of humans and animals, especially their kidneys. Our study explores OTA's effects on the gut microbiota and kidney damage while examining how postbiotics offer protection. Using metagenomic sequencing, we observed that OTA increased the potential gut pathogens such as Alistipes, elevating detrimental metabolites and inflammation. Also, OTA inhibited the Nrf2/HO-1 pathway, reducing kidney ROS elimination and leading to cellular ferroptosis and subsequent kidney damage. Postbiotics mitigate OTA's effects by downregulating the abundance of the assimilatory sulfate reduction IV pathway and virulence factors associated with iron uptake and relieving the inhibition of OTA on Nrf2/HO-1, restoring ROS-clearing capabilities and thereby alleviating chronic OTA-induced kidney damage. Understanding the OTA-gut-kidney link provides new approaches for preventing kidney damage, with postbiotics showing promise as a preventive treatment.

Genomic characterization of a multidrug-resistant uropathogenic <i>Escherichia coli</i> and evaluation of <i>Echeveria</i> plant extracts as antibacterials

<abstract> <p>Uropathogenic <italic>Escherichia coli</italic> (UPEC) is the most common bacterial agent associated with urinary tract infections, threatening public health systems with elevated medical costs and high morbidity rates. The successful establishment of the infection is associated with virulence factors encoded in its genome, in addition to antibacterial resistance genes, which could limit the treatment and resolution of the infection. In this sense, plant extracts from the genus <italic>Echeveria</italic> have traditionally been used to treat diverse infectious diseases. However, little is known about the effects of these extracts on bacteria and their potential mechanisms of action. This study aims to sequence a multidrug-resistant UPEC isolate (UTI-U7) and assess the multilocus sequence typing (MLST), virulence factors, antimicrobial resistance profile, genes, serotype, and plasmid content. Antimicrobial susceptibility profiling was performed using the Kirby-Bauer disk diffusion. The antibacterial and anti-adherent effects of the methanol extracts (ME) of <italic>Echeveria</italic> (<italic>E. craigiana</italic>, <italic>E. kimnachii</italic>, and <italic>E. subrigida</italic>) against UTI-U7 were determined. The isolate was characterized as an O25:H4-B2-ST2279-CH40 subclone and had resistant determinants to aminoglycosides, β-lactams, fluoroquinolones/quinolones, amphenicols, and tetracyclines, which matched with the antimicrobial resistance profile. The virulence genes identified encode adherence factors, iron uptake, protectins/serum resistance, and toxins. Identified plasmids belonged to the IncF group (IncFIA, IncFIB, and IncFII), alongside several prophage-like elements. After an extensive genome analysis that confirmed the pathogenic status of UTI-U7 isolate, <italic>Echeveria</italic> extracts were tested to determine their antibacterial effects; as an extract, <italic>E. subrigida</italic> (MIC, 5 mg/mL) displayed the best inhibitory effect. However, the adherence between UTI-U7 and HeLa cells was unaffected by the ME of the <italic>E. subrigida</italic> extract.</p> </abstract>

Iron deficiency anemia: a critical review on iron absorption, supplementation and its influence on gut microbiota.

Iron deficiency anemia (IDA) caused by micronutrient iron deficiency has attracted global attention due to its adverse health effects. The regulation of iron uptake and metabolism is finely controlled by various transporters and hormones in the body. Dietary iron intake and regulation are essential in maintaining human health and iron requirements. The review aims to investigate literature concerning dietary iron intake and systemic regulation. Besides, recent IDA treatment and dietary iron supplementation are discussed. Considering the importance of the gut microbiome, the interaction between bacteria and micronutrient iron in the gut is also a focus of this review. The iron absorption efficiency varies considerably according to iron type and dietary factors. Iron fortification remains the cost-effective strategy, although challenges exist in developing suitable iron fortificants and food vehicles regarding bioavailability and acceptability. Iron deficiency may alter the microbiome structure and promote the growth of pathogenic bacteria in the gut, affecting immune balance and human health.

Transferrin receptor 1 rs3817672 variant genotyping in Egyptian children diagnosed with iron-deficiency anemia: a case–control study

Background Cell surface transferrin receptor 1 (TFR1) is a gatekeeper controling cellular iron uptake. The association of iron-deficiency anemia (IDA) in humans with TFR1 variants was not extensively studied. Among these variants is TFR1 rs3817672, an exonic missense variation that may affect the TFR1 protein structure. This is the first study in Egypt and the second worldwide that genotype TFR1 rs3817672 variant in IDA pediatric patients. Aim The aim of the current study was to investigate the association between TFR1 rs3817672 variant with susceptibility risk for IDA. Patients and methods The study was conducted on 50 IDA Egyptian pediatric patients and 50 healthy controls. Complete blood count, iron profile, and TFR1 rs3817672 variant genotyping were performed for all participants. Results TT genotype was associated with a high risk of IDA among cases compared to controls in the recessive model (odds ratio 24, 95% confidence interval 5.253–109.650, P≤0.001) with the predominance of T allele (odds ratio 7.3187, 95% confidence interval 3.919–13.669, P≤0.001). TT genotype was associated with a significant decrease in serum iron (P=0.001 and 0.003) and transferrin saturation (P=0.003 and 0.005) compared to CT genotype and CC+CT genotypes in the recessive model, respectively. In IDA patients, serum iron had a significant positive correlation with transferrin saturation (r=0.984, P≤0.001) and a significant negative correlation with total iron-binding capacity (r=−0.555, P≤0.001). Conclusion TT genotype was the predominant genotype among Egyptian pediatric IDA patients. TFR1 rs3817672 genotyping might be used as a potential screening test for IDA risk susceptibility in pediatrics.

The effect of iron absorption in ferrous gluconate form from enriched rice flour using an in vitro digestion model and a Caco-2 cell model.

Iron deficiency can cause serious diseases in infants and young children such as indigestion, anemia, and nervous system dysplasia. Consumption of high-iron rice flour can prevent iron deficiency. The objective of this study was to evaluate the potential application of ferrous gluconate as an iron source in high-iron rice flour used as a type of accessory food for infants and young children. In this study, the differences in iron absorption ability between ferrous gluconate and ferrous fumarate in rice flour with the same ingredients in both high and low phytic acid systems were evaluated. The results showed that there was no significant difference in the bioaccessibility/bioavailability between ferrous gluconate and ferrous fumarate at both low and high phytic acid contents. In low phytic acid and high phytic acid systems, the iron absorption rate of ferrous gluconate is 11.53% and 13.45% higher than that of ferrous fumarate, respectively (p < 0.05). In summary, the iron absorption rate of ferrous gluconate was higher than that of ferrous fumarate in the rice flour system. Additionally, the low phytic acid environment is more conducive to iron uptake and utilization. Therefore, ferrous gluconate can be used as an alternative source of iron in accessory foods for infants and young children.

New Drug Discovery Targeting Iron in Bacterial Infectious Diseases

Iron is necessary for all living organisms, and bacteria that cause infections in human hosts also need ferrous ions for their growth and proliferation. In the human body, most ferric ions (Fe3+) are tightly bound to iron-binding proteins such as hemoglobin, transferrin, lactoferrin, and ferritin. Pathogenic bacteria express highly specific iron uptake systems, including siderophores and specific receptors. Most bacteria secrete siderophores, which are low-molecular weight metal-chelating agents, to capture Fe3+ outside cell. Siderophores are mainly classified as either catecholate or hydroxamate. Vibrio vulnificus, a Gram-negative pathogenic bacterium, is responsible for serious infections in humans and requires iron for growth. A clinical isolate, V. vulnificus M2799, secretes a catecholate siderophore, vulnibactin, that captures ferric ions from the environment. In our study, we generated deletion mutants of the genes encoding proteins involved in the vulnibactin mediated iron-utilization system, such as ferric-vulnibactin receptor protein (VuuA), periplasmic ferric-vulnibactin binding protein (FatB), ferric-vulnibactin reductase (VuuB), and isochorismate synthase (ICS). ICS and VuuA are required under low-iron conditions for ferric-utilization in M2799, but the alternative proteins FatB and VuuB can function as a periplasmic binding protein and a ferric-chelate reductase, respectively. VatD, which functions as ferric-hydroxamate siderophores periplasmic binding protein, was shown to participate in the ferric-vulnibactin uptake system in the absence of FatB. Furthermore, the ferric-hydroxamate siderophore reductase IutB was observed to participate in ferric-vulnibactin reduction in the absence of VuuB. We propose that ferric-siderophore periplasmic binding proteins and ferric-chelate reductases represent potential targets for drug discovery in the context of infectious diseases.

Effect of anti-biofilm peptide CRAMP-34 on the biofilms of Acinetobacter lwoffii derived from dairy cows.

Dairy mastitis is one of the most common diseases in dairy farming, and the formation of pathogenic bacteria biofilms may be an important reason why traditional antibiotic therapy fails to resolve some cases of dairy mastitis. We isolated and identified three strains of A. lwoffii were with strong biofilm forming ability from dairy cow mastitis samples from Chongqing dairy farms in China. In order to investigate the effect of novel anti-biofilm peptide CRAMP-34 on A.lwoffii biofilms, the anti-biofilm effect was evaluated by crystal violet staining, biofilms viable bacteria counting and confocal laser scanning microscopy (CLSM). In addition, transcriptome sequencing analysis, qRT-PCR and phenotypic verification were used to explore the mechanism of its action. The results showed that CRAMP-34 had a dose-dependent eradicating effect on A. lwoffii biofilms. Transcriptome sequencing analysis showed that 36 differentially expressed genes (11 up-regulated and 25 down-regulated) were detected after the intervention with the sub-inhibitory concentration of CRAMP-34. These differentially expressed genes may be related to enzyme synthesis, fimbriae, iron uptake system, capsular polysaccharide and other virulence factors through the functional analysis of differential genes. The results of subsequent bacterial motility and adhesion tests showed that the motility of A.lwoffii were enhanced after the intervention of CRAMP-34, but there was no significant change in adhesion. It was speculated that CRAMP-34 may promote the dispersion of biofilm bacteria by enhancing the motility of biofilm bacteria, thereby achieving the effect of eradicating biofilms. Therefore, these results, along with our other previous findings, suggest that CRAMP-34 holds promise as a new biofilm eradicator and deserves further research and development.

Unveiling the Antimicrobial Potential of 7-O-succinyl Macrolactin F from Bacillus subtilis Group against HtsA Siderophore Receptor of Staphylococcus aureus: A Computational Exploration

Background: Staphylococcus aureus remains a prominent pathogen within health-care environments due to its extensive repertoire of virulence factors. The escalating prevalence of antibiotic-resistant strains has underscored the urgency of identifying alternative treatment strategies. The study focuses on the HtsA siderophore receptor, an integral cell wall component of all S. aureus strains, responsible for iron acquisition from the host environment. Here, we investigate the potential of Bacillus sp. derived macrolides as inhibitors of this critical iron uptake mechanism. Methods: Sixteen distinct macrolide ligands were evaluated for their ability to disrupt iron acquisition by S. aureus through interaction with the HtsA receptor. Employing molecular docking and subsequent molecular dynamics (MDs) simulations, the binding interactions and dynamic behaviors of these ligands with the receptor were assessed. Results: Notably, the complex formed between 7-O-succinyl macrolactin F and HtsA demonstrated a good binding affinity of − 8.5 kcal/mol, outperforming the binding affinity of staphyloferrin A, which exhibited a binding affinity of − 6.9 kcal/mol. MD simulations further corroborated the stability of the 7-O-succinyl macrolactin F-HtsA complex over time, suggesting the potential for this interaction to be harnessed as a novel therapeutic strategy not only for existing antibiotic-resistant strains but also for those that may arise in the future. Conclusion: The findings propose Bacillus species-derived macrolides as potential adjuvant therapies for S. aureus infections, pending comprehensive safety assessments. This research lays the foundation for the development of innovative antimicrobial agents targeting essential virulence-associated mechanisms in S. aureus.