Metschnikowia citriensis FL01 antagonize Geotrichum citri-aurantii in citrus fruit through key action of iron depletion

Metschnikowia citriensis FL01 has great potential for biocontrol applications for its excellent biocontrol efficacy on postharvest diseases of citrus fruit, and the iron depletion by pulcherriminic acid (PA) and then formation of insoluble pigment pulcherrimin had been speculated as an important action mechanism. To identify the genes involved in pulcherrimin synthesis and reutilization in M. citriensis FL01, we de novo assembled the genome of M. citriensis FL01 based on long-read PacBio sequencing. The final assembled genome consisted of 12 contigs with a genome size of 25.74 Mb, G + C content of 49.16% and 9310 protein-coding genes. The genome-wide BLAST of the PUL genes of M. pulcherrima APC 1.2 showed that the four PUL genes were clustered and located on Contig 4 of M. citriensis FL01. In order to further clarify the role of pulcherrimin pigment on biocontrol of M. citriensis FL01, CRISPR/cas9 technology was used to knock out PUL2 gene that was responsible for PA synthesis and the pigmentless mutants with stable phenotype were obtained. The mutant strains of M. citriensis FL01 lost the ability to produce pulcherrimin pigment, and simultaneously lost the ability to inhibit the growth of Geotrichum citri-aurantii in vitro. Moreover, the biocontrol efficacy of pigmentless mutant strains against sour rot was about 80% lower than that of wild-type M. citriensis FL01. These results directly proved that the iron depletion was an important mechanism of M. citriensis FL01.

Easy detection of siderophore production in diluted growth media using an improved CAS reagent

Siderophores are low molecular weight organic compounds produced by various microorganisms, especially pathogenic bacteria including rhizobacteria, and have a high affinity for iron. Although most microorganisms are thought to secrete siderophores under iron-depleted conditions, it is unclear how many microorganisms produce siderophores in the natural environment. Also, the chrome azurol sulfonate (CAS) assay, which is widely used for the detection of siderophores, needs to be improved for wider applicability. We developed a simple, high-throughput CAS assay in a 96-well microplate with a concentrated CAS reagent and commonly used diluted growth media in the absence of artificial iron depletion. The improved microplate CAS shuttle assay revealed that it could easily detect siderophores released from Pseudomonas (P.) fluorescence, P. putida, Burlkholderia stabilis, and Ottowia oryzae, as models of siderophore-producing bacteria. This CAS shuttle assay employed along with diluted growth media is a promising tool to screen new siderophore-producing bacteria.

Iron deficiency as therapeutic target in heart failure: a translational approach

Heart failure (HF) is a potentially debilitating condition, with a prognosis comparable to many forms of cancer. It is often complicated by anemia and iron deficiency (ID), which have been shown to even further harm patients' functional status and hospitalization risk. Iron is a cellular micronutrient that is essential for oxygen uptake and transportation, as well as mitochondrial energy production. Iron is crucially involved in electrochemical stability, maintenance of structure, and contractility of cardiomyocytes. There is mounting evidence that ID indeed hampers the homeostasis of these properties. Animal model and stem cell research has verified these findings on the cellular level, while clinical trials that treat ID in HF patients have shown promising results in improving real patient outcomes, as electromechanically compromised cardiomyocytes translate to HF exacerbations and arrhythmias in patients. In this article, we review our current knowledge on the role of iron in cardiac muscle cells, the contribution of ID to anemia and HF pathophysiology and the capacity of IV iron therapy to ameliorate the patients' arrhythmogenic profile, quality of life, and prognosis.

In vitro inhibition of Saccharomyces cerevisiae growth by Metschnikowia spp. triggered by fast removal of iron via two ways

Simple and convenient innovative assays in vitro demonstrating Metschnikowia spp. competition with Saccharomyces cerevisiae for an essential nutrient iron are presented. The tested Metschnikowia strains possess a common genetically determined property of secreting a pulcherriminic acid which in the presence of iron (III) ions forms an insoluble red pigment pulcherrimin. Both initial accumulation in growing Metschnikowia cells and subsequent precipitation in the form of pulcherrimin in the media contribute to iron removal by functioning cells. The predominant way depends on the strain. Due to fast elimination of iron, the growth of S. cerevisiae can be inhibited by tested Metschnikowia strains at concentrations of elemental iron in the media not exceeding 12 mg kg^-1. Inhibition can be regulated by additional supply of microquantities of iron onto the surface of the solid medium within 20-24 h. At relatively low concentrations of elemental iron (below 1 mg kg^-1), additional supplements of iron onto the surface provide an advancement in understanding the inhibition possibilities and enable the assay control. Microscopy observations revealed that Metschnikowia chlamydospores are involved in iron removal at relatively high iron concentrations. The results may find application in development of new methodologies and strategies for biocontrol or inhibition of pathogenic microorganisms.

Biocontrol ability and action mechanism of Metschnikowia citriensis against Geotrichum citri-aurantii causing sour rot of postharvest citrus fruit

This study investigated the biocontrol efficiency of Metschnikowia citriensis strain FL01 against Geotrichum citri-aurantii, and evaluated possible mechanisms. The results showed that M. citriensis could effectively control the development of sour rot, and significantly inhibit the mycelial growth and spore germination of G. citri-aurantii. The population dynamics results and Scanning electron microscopy (SEM) analysis indicated that M. citriensis could rapidly colonize wounds and tightly adhere to the surface of the wounds to compete with G. citri-aurantii for nutrition and space. M. citriensis also showed the biofilm formation action in vitro. The response of G. citri-aurantii to different components of M. citriensis culture showed that only the yeast cells but not the extracellular metabolites and the volatile organic compounds (VOCs) exhibited inhibitory effect on the growth of G. citri-aurantii. M. citriensis adhered to the hyphae of G. citri-aurantii loosely and sparsely, and the production of lytic enzymes β-1, 3-glucanase (GLU) and Chitinase (CHI) could not be induced by G. citri-auranti. Iron affected the pulcherrimin pigment production and antagonism of M. citriensis indicating iron depletion as the most important antagonistic mechanism. Besides, M. citriensis also induced resistance of fruit against sour rot. These results suggested that M. citriensis could be used as the potential alternative of fungicides to control postharvest pathogens on citrus fruit.

Iron Depletion in Adult and Teenage Blood Donors: Prevalence, Clinical Impact, and Options for Mitigation

Iron depletion is a known risk for adult blood donors, but recent studies indicate the prevalence of iron depletion is higher in teenage blood donors. Teenage donors account for more than 10% of the blood collected in the United States and are important for maintaining component availability. Evidence of harm from iron depletion has not been demonstrated, but the area would benefit from further scientific inquiry. Options to protect against iron depletion exist, but each has limitations including cost, logistics, and potential negative impact on blood supply. Blood centers should communicate with donors and make efforts to mitigate these risks.

Detection of Iron Depletion- and Hypoxia-Induced Mitophagy in Mammalian Cells

Mitochondrial autophagy or mitophagy is a process that selectively degrades mitochondria via autophagy. It is believed that mitophagy degrades damaged or unnecessary mitochondria and is important for maintaining mitochondrial homeostasis. To date, it is known that several stimuli can induce mitophagy. However, some of these stimuli (including iron depletion, hypoxia, and nitrogen starvation) induce mild mitophagy, which is difficult to detect by measuring the decrease in mitochondrial mass. Recently, we have successfully detected mitophagy induced under these conditions using mito-Keima as a reporter. In this chapter, we describe the protocols for induction and detection of iron depletion- and hypoxia-induced mitophagy using the mito-Keima-expressing cells.

Iron depletion induces hepatic secretion of biliary lipids and glutathione in rats

Iron depletion (ID) has been shown to induce the liver expression of Cyp7a1, the rate-limiting enzyme initiating conversion of cholesterol to bile acids (BA), although the effect on bile acids metabolism and bile production is unknown. Therefore, we investigated changes in bile secretion and BA synthesis during diet-induced iron depletion (ID) in rats. ID increased bile flow along with augmented biliary excretion of bile acids, glutathione, cholesterol and phospholipids. Accordingly, we found transcriptional upregulation of the Cyp7a1, Cyp8b1, and Cyp27a1 BA synthetic enzymes, as well as induction of the Abcg5/8 cholesterol transporters in ID rat livers. In contrast, intravenous infusion of ³H-taurocholate failed to elicit any difference in biliary secretion of this compound in the ID rats. This corresponded with unchanged expression of canalicular rate-limiting transporters for BA as well as glutathione. We also observed that ID substantially changed the spectrum of BA in bile and decreased plasma concentrations of BA and cholesterol. Experiments with differentiated human hepatic HepaRG cells confirmed human CYP7A1 orthologue upregulation resulting from reduced iron concentrations. Results employing a luciferase reporter gene assay suggest that the transcriptional activation of the CYP7A1 promoter under ID conditions works independent of farnesoid X (FXR), pregnane X (PXR) and liver X (LXRα) receptors activation. It can be concluded that this study characterizes the molecular mechanisms of modified bile production as well as cholesterol as along with BA homeostasis during ID. We propose complex upregulation of BA synthesis, and biliary cholesterol secretion as the key factors affected by ID.

Data on the effects of low iron diet on serum lipid profile in HCV transgenic mouse model

Here, we presented new original data on the effects of iron depletion on the circulating lipid profile in B6HCV mice, a murine model of HCV-related dyslipidemia. Male adult B6HCV mice were subjected to non-invasive iron depletion by low iron diet. Serum iron concentration was assessed for evaluating the effects of the dietary iron depletion. Concentrations of circulating triglycerides, total cholesterol, Low Density Lipoproteins (LDLs), High Density Lipoproteins (HDLs) were analyzed and reported by using stacked line charts. The present data indicated that low serum iron concentration is associated to i) lower serum triglycerides concentrations and ii) increased circulating LDLs. The presented original data have not been published elsewhere.

Iron depletion strategy for targeted cancer therapy: utilizing the dual roles of neutrophil gelatinase-associated lipocalin protein

Decreasing iron uptake and increasing iron efflux may result in cell death by oxidative inactivation of vital enzymes. Applying the dual function of neutrophil gelatinase-associated lipocalin (NGAL) could achieve the goal of iron depletion in the cancer cells. Tyr106, Lys125 or Lys134 was the key binding site for NGAL protein to sequester iron-chelating siderophores. In this study, we employed all bioactive peptides in peptide databank to dock with the siderophore-binding sites of NGAL protein by virtual screening. In addition, we performed molecular dynamics (MD) simulation to observe the molecular character and structural variation of ligand-protein interaction. Glu-Glu-Lys-Glu (EEKE), Glu-Glu-Asp-Cys-Lys (EEDCK), and Gly-Glu-Glu-Cys-Asp (GEECD) were selected preliminarily by rigorous scoring functions for further investigation. GEECD was excluded due to higher binding total energy than the others. Moreover, we also excluded EEKE due to larger influence to the stability of binding residues by the information of root mean square fluctuation (RMSF) and principal component analysis (PCA). Thus, we suggested that EEDCK was the potential bioactive peptide which had been proved to inhibit malignant cells for targeted cancer therapy. Graphical Abstract Perspective drug design of occupying the siderophore-binding sites of NGAL outside the cell temporarily by a potential short peptide until NGAL enters into the cell, and releasing the siderophore-binding sites inside the cell.

A randomized trial of iron depletion in patients with nonalcoholic fatty liver disease and hyperferritinemia

AIM: To compare iron depletion to lifestyle changes alone in patients with severe nonalcoholic fatty liver disease (NAFLD) and hyperferritinemia, a frequent feature associated with more severe liver damage, despite at least 6 mo of lifestyle changes.

METHODS: Eligible subjects had to be 18-75 years old who underwent liver biopsy for ultrasonographically detected liver steatosis and hyperferritinemia, ferritin levels ≥ 250 ng/mL, and NAFLD activity score > 1. Iron depletion had to be achieved by removing 350 cc of blood every 10-15 d according to baseline hemoglobin values and venesection tolerance, until ferritin < 30 ng/mL and/or transferrin saturation (TS) < 25%. Thirty-eight patients were randomized 1:1 to phlebotomy (n = 21) or lifestyle changes alone (n = 17). The main outcome of the study was improvement in liver damage according to the NAFLD activity score at 2 years, secondary outcomes were improvements in liver enzymes [alanine aminotransferases (ALT), aspartate aminotransferase (AST), and gamma-glutamyl-transferases (GGT)].

RESULTS: Phlebotomy was associated with normalization of iron parameters without adverse events. In the 21 patients compliant to the study protocol, the rate of histological improvement was higher in iron depleted vs control subjects (8/12, 67% vs 2/9, 22%, P = 0.039). There was a better improvement in steatosis grade in iron depleted vs control patients (P = 0.02). In patients followed-up at two years (n = 35), ALT, AST, and GGT levels were lower in iron-depleted than in control patients (P < 0.05). The prevalence of subjects with improvement in histological damage or, in the absence of liver biopsy, ALT decrease ≥ 20% (associated with histological improvement in biopsied patients) was higher in the phlebotomy than in the control arm (P = 0.022). The effect of iron depletion on liver damage improvement as assessed by histology or ALT decrease ≥ 20% was independent of baseline AST/ALT ratio and insulin resistance (P = 0.0001).

CONCLUSION: Iron depletion by phlebotomy is likely associated with a higher rate of improvement of histological liver damage than lifestyle changes alone in patients with NAFLD and hyperferritinemia, and with amelioration of liver enzymes.

High concentrations of hexavalent chromium in drinking water alter iron homeostasis in F344 rats and B6C3F1 mice

Hexavalent chromium [Cr(VI)] induces hematological signs of microcytic anemia in rodents. Considering that Cr(VI) can oxidize ferrous (Fe(2+)) to ferric (Fe(3+)) iron, and that only the former is transported across the duodenum, we hypothesize that, at high concentrations, Cr(VI) oxidizes Fe(2+) in the lumen of the small intestine and perturbs iron absorption. Herein we report that 90-day exposure to Cr(VI) in drinking water resulted in dose-dependent decreases in Fe levels in the duodenum, liver, serum, and bone marrow. Toxicogenomic analyses from the duodenum indicate responses consistent with Fe deficiency, including significant induction of divalent metal transporter 1 (DMT1, Slc11a2) and transferrin receptor 1 (TFR1, Tfr1). In addition, at ⩾20mg Cr(VI)/L in drinking water, Cr RBC:plasma ratios in rats were increased and exceeded unity, indicating saturation of reductive capacity and intracellular absorption of Cr(VI) into red blood cells (RBCs). These effects occurred in both species but were generally more severe in rats. These data suggest that high concentrations of Cr(VI) in drinking limit Fe absorption and alter iron homeostasis. Furthermore, some effects observed at high doses in recent Cr(VI) chronic and subchronic bioassays may be explained, at least in part, by iron deficiency and disruption of homeostasis.

Iron status and developmental scores in 6-year-olds highlights ongoing need to tackle iron deficiency in infants

AIM

To investigate iron status and developmental scores at 6 years of age in a population with decreased prevalence of iron deficiency in infancy. Iron status at 6 years and tracking from 12 months were also studied.

METHODS

Children (n = 143) born in Iceland in 2005 were followed up at the age of six. Motor and verbal development was assessed by a parental questionnaire, and iron status was assessed by Hb, MCV and serum ferritin (SF). Iron depletion was defined as SF <15 μg/L and deficiency as MCV <76 fL and SF <15 μg/L.

RESULTS

Iron depletion was observed in 5.6% of 6-year-olds, and 1.4% were iron deficient. Self-help (subset in motor development) differed by -4.14 (95% CI = -7.61, -0.67), between those iron depleted at 12 months (n = 6) and those nondepleted (n = 102), adjusted for maternal education. The combined motor developmental score seemed lower in iron depleted infants, although of borderline significance (p = 0.066). MCV concentration tracked from 12 months to 6 years (r = 0.31, p < 0.002), but Hb and SF did not.

CONCLUSION

Improved iron status at 12 months and 6 years has diminished the public health threat associated with iron depletion in the population studied, but iron depletion and development still associate weakly. Action to prevent iron depletion in infancy remains important.

The prevalence of anemia and iron depletion in the population aged 10 years or older

Background

Anemia and iron depletion continue to be common disorders in the world. This study was aimed at assessing the prevalence of anemia and iron depletion in apparently healthy Koreans aged 10 years or more.

Methods

We used the data of the 4^th Korean National Health & Nutrition Examination Survey (KNHANES), which assessed 7,607 individuals (3,337 males and 4,270 females). Iron depletion was defined as serum ferritin less than 15 ng/mL.

Results

In males, mean hemoglobin (Hb) concentration decreased after the age of 50. The prevalence of anemia was 7.1% in 60 to 69 year olds and 12.3% in men aged 70 or older. As for females, the prevalence of anemia was 8.8% in 15 to 17 year olds, 16.7% in 18 to 49 year olds, 10.9% in 60 to 69 year olds, and 18.2% women aged 70 or older. In males, the prevalence of iron depletion was 8.6% at ages 10 to 14 years, 3.9% at 15 to 17, and 2.6% at 70 years or older. In females, the prevalence of iron depletion was 17.2% at ages 10 to 14 years, 24.1% at 15 to 17, 33.0% at 18 to 49, and 5.7% at 70 years or older. Although normocytic anemia was most common in both males and females, the proportion of microcytosis and macrocytosis increased at age 70 or older.

Conclusion

The prevalence of anemia and iron depletion was high in women of reproductive age and in the elderly. Considering the rapid increase in the older population, an intervention to prevent anemia and iron depletion is imperative.