Metallomics最新文献

Trace metals are indispensable nutritional factors for all living organisms. During host-pathogen interactions, they serve as crucial resources that dictate infection outcomes. Accordingly, the host uses a defense strategy known as nutritional immunity, which relies on coordinated metal chelation to mitigate bacterial advances. In response, pathogens employ complex strategies to secure these resources at sites of infection. In the gastrointestinal (GI) tract, the microbiota must also acquire metals for survival, making metals a central line of competition in this complex ecosystem. In this minireview, we outline how bacteria secure iron, zinc, and manganese from the host with a focus on the GI tract. We also reflect on how host dietary changes impact disease outcomes and discuss therapeutic opportunities to target bacterial metal uptake systems. Ultimately, we find that recent discoveries on the dynamics of transition metals at the host-pathogen-microbiota interface have reshaped our understanding of enteric infections and provide insights into virulence strategies, microbial cooperation, and antibacterial strategies.

Cupriavidus metallidurans CH34 is a metal-resistant bacterium. Its metal homeostasis is based on a flow equilibrium of metal ion uptake and efflux reactions, which adapts to changing metal concentrations within an hour. At high metal concentrations, up-regulation of the genes for metal efflux systems occurs within minutes. Here, we investigates the changes in the bacterial proteome accompanying these genetic and physiological events after 1.5 cell duplications, which took 3 hours. To that end, C. metallidurans CH34 and its plasmid-free derivative, AE104, were challenged either with a toxic metal mix or were cultivated under metal-starvation conditions, followed by bottom-up proteomics. When metal-shocked or -starved cells were compared with their respective controls, 3 540 proteins changed in abundance, with 76% appearing in one, but not the other, condition; the remaining 24% were up- or down-regulated. Metal-shocked C. metallidurans strains had adjusted their proteomes to combat metal stress. The most prominent polypeptides were the products of the plasmid-encoded metal-resistance determinants in strain CH34, particularly the CzcCBA transenvelope efflux system. Moreover, the influence of antisense transcripts on the proteome was also revealed. In one specific example, the impact of an asRNA on the abundance of gene products could be demonstrated and this yielded new insights into the function of the transmembrane efflux complex ZniCBA under conditions of metal starvation.

Cupriavidus metallidurans is able to thrive in metal-rich environments but also survives metal starvation. Expression of metal resistance determinants in C. metallidurans was investigated on a global scale. C. metallidurans was challenged with a MultiTox metal mix specifically designed for the wildtype strain CH34 and its plasmid-free derivative AE104, including treatment with ethylenediamintetraacetate (EDTA), or without challenge. The sense and antisense transcripts were analyzed in both strains and under all three conditions by RNASeq. A total of 10 757 antisense transcripts (ASTs) were assigned to sense signals from genes and untranslated regions, and 1 319 of these ASTs were expressed and were longer than 50 bases. Most of these (82%) were dual-use transcripts that contained antisense and sense regions, but ASTs (16%) were also observed that had no sense regions. Especially in metal-treated cells of strains CH34 and AE104, up- or down-regulated sense transcripts were accompanied by antisense transcription activities that were also regulated. The presence of selected asRNAs was verified by RT-PCR. Following metal stress, expression of genes encoding components of the respiratory chain, motility, transcription, translation and protein export were down-regulated. This should also affect the integration of the metal efflux pumps into the membrane and the supply of the energy required to operate them. To solve this dilemma, transcripts for the metal efflux pumps may be stabilized by interactions with ASTs to allow their translation and import into the membrane. Alternatively, metal stress possibly causes recruitment of RNA polymerase from housekeeping genes for preferential expression of metal resistance determinants.

Kidney stones, as typical biominerals produced within the human body, pose a significant threat to human health, affecting over 12% of the global population. However, the exact mechanisms underlying their formation are not fully understood. Recent metal isotopic analysis provides a new way to study the roles of metal cations in biological processes within organisms. Here we report the Mg isotope ratios of human kidney stones for the first time. The total range of measured values for δ26Mg in kidney stones is 1.05‰, from-1.12‰ to-0.07‰. Our data exhibit a significant 24Mg enrichment compared with the values calculated from density functional theory. We suggest that the Mg-isotopic fractionations in vivo are linked to active Mg transport mediated by proteins during intestinal absorption and preferential renal reabsorption of ionized Mg2+ via tight junctional proteins. Our results indicate that the inhibitory effect of Mg on kidney stones is related to the kink-blocking mechanism, and the incorporation of hydrated Mg lessens the extent of inhibition and the magnitude of isotope discrimination. We show that metal isotopes provide new insights into the underlying the biological processes and human health.

The shell color of Corbicula clams, which are globally distributed, is roughly divided into yellowish and blackish depending on the environmental conditions of the sediment. The formation of an iron-L-3,4-dihydroxyphenylalanine (DOPA) complex in a thin organic layer, called the periostracum, on a calcareous layer causes the blackening of the clamshell. However, the iron-DOPA complex formation mechanism is unclear. To reveal how the iron is transported from the aquatic environment to the periostracum, cross-sectional analyses of the shell were conducted using an electron probe microanalyzer (EPMA) and Raman spectroscopy to investigate the distribution and structure of iron in the shell. Iron was only present in the periostracum, excluding deposition, and all iron was in the form of an iron-DOPA complex. Attenuated total reflection infrared spectroscopy and oxygen K-edge X-ray absorption fine structure spectroscopy revealed that the molecular structure of the native periostracum is independent of shell color. These results indicate that dissolved iron-organic complexes diffuse from the aqueous environment to the periostracum, forming iron-DOPA complex through ligand exchange. Because the iron-DOPA complex color depends on the pH, the shell color can serve as a historical indicator of the shell's growth environment.

The brain is a privileged organ with regards to its trace element composition and maintains a robust barrier system to sequester this specialized environment from the rest of the body and the vascular system. Stroke is caused by loss of adequate blood flow to a region of the brain. Without adequate blood flow ischemic changes begin almost immediately, triggering an ischemic cascade, characterized by ion dysregulation, loss of function, oxidative damage, cellular degradation, and break down of the barrier that helps maintain this environment. Ion dysregulation is a hallmark of stroke pathophysiology and we observe that most elements in the brain are dysregulated after stroke. X-ray fluorescence-based detection of physiological changes in the neurometallome after stroke reveals profound ion dysregulation within the lesion and surrounding tissue. Not only are most elements significantly dysregulated after stroke, but the level of dysregulation cannot be predicted from a cell-level description of dysregulation. X-ray fluorescence imaging reveals that the stroke lesion retains < 25% of essential K+ after stroke, but this element is not concomitantly elevated elsewhere in the organ. Moreover, elements like Na+, Ca2+, and Cl- are vastly elevated above levels available in normal brain tissue (>400%, >200%, and > 150%, respectively). We hypothesize that weakening of the blood-brain-barrier after stroke allows elements to freely diffuse down their concentration gradient so that the stroke lesion is in equilibrium with blood (and the compartments containing brain interstitial fluid and cerebrospinal fluid). The changes observed for the neurometallome likely has consequences for the potential to rescue infarcted tissue, but also presents specific targets for treatment.

Transition metals like copper, iron, and zinc are vital for normal central nervous system function and are also linked to neurodegeneration, particularly in the onset and progression of Alzheimer's disease (AD). Their alterations in AD, identified prior to amyloid plaque aggregation, offer a unique target for staging pre-amyloid AD. However, analysing their levels in the brain is extremely challenging, necessitating the development of alternative approaches. Here, we utilised laser ablation-inductively coupled plasma-mass spectrometry and solution nebulisation-inductively coupled plasma-mass spectrometry to quantitatively measure Cu, Fe, and Zn concentrations in the retina and hippocampus samples obtained from human donors (i.e., AD and healthy controls), and in the APP/PS1 mouse model of AD, and Wild Type controls, aged 9 and 18 months. Our findings revealed significantly elevated Cu, Fe, and Zn levels in the retina (*p < 0.05, **p < 0.01, ***p < 0.001) and hippocampus (*p < 0.05, *p < 0.05, *p < 0.05) of human AD samples compared to healthy controls. Conversely, APP/PS1 mouse models exhibited notably lower metal levels in the same regions compared to WT mice, Cu, Fe, and Zn levels in the retina (**p < 0.01, *p < 0.05, *p < 0.05) and hippocampus (**p < 0.01, **p < 0.01, *p < 0.05). The contrasting metal profiles in human and mouse samples, yet similar patterns within each species' retina and brain, suggest the retina mirrors cerebral metal dyshomeostasis in AD. Our findings lay the groundwork for staging pre-AD pathophysiology through assessment of transition metal levels in the retina.

Calcium (Ca) isotopes in blood/urine are emerging biomarkers of bone mineral balance (BMB) in the human body. While multiple studies have investigated Ca isotopes in patients suffering from diseases affecting BMB, comparatively little effort has been devoted to understanding the homeostasis of Ca isotopes in healthy individuals. Here, we report on a longitudinal study of the urine Ca isotope composition (δ44/42CaUrine) from 22 healthy participants (age 19-60) over timescales ranging from days to months. Data from a single participant collected over a 30-day period show that morning urine is an excellent proxy for 24-h pooled urine fractions. Data from all participants reveal large inter-individual variability in δ44/42CaUrine (up to 2.2‰), which is partly due to anthropometric differences, as shown by a correlation between the participants' body mass index (BMI) and δ44/42CaUrine values. In contrast, intra-individual data reveal encouraging stability (within ∼±0.2-0.3‰) over timescales >160 days, indicating that self-referencing approaches for BMB monitoring hold greater promise than cross-sectional ones. Our data confirm that intra-individual δ44/42CaUrine variations are mainly a function of Ca reabsorption in the kidney, but also reveal the impact of other (and at times equally important) drivers, such as diet, alcohol consumption, physical exercise, or fasting. We also find that a magnetic resonance imaging contrast agent (gadolinium) can lead to artifacts during Ca isotope analysis. Based on our results, a series of practical considerations for the use of Ca isotopes in urine as tracers of BMB are presented.

Streptomyces scabiei is the causative agent of common scab on root and tuber crops. Life in the soil imposes intense competition between soil-dwelling microorganisms, and we evaluated here the antimicrobial properties of S. scabiei. Under laboratory culture conditions, increasing peptone levels correlated with increased growth inhibitory properties of S. scabiei. Comparative metabolomics showed that production of S. scabiei siderophores (desferrioxamines, pyochelin, scabichelin, and turgichelin) increased with the quantity of peptone, thereby suggesting that they participate in growth inhibition. Mass spectrometry imaging further confirmed that the zones of secreted siderophores and growth inhibition coincided. Moreover, either the repression of siderophore production or the neutralization of their iron-chelating activity led to increased microbial growth. Replacement of peptone by natural nitrogen sources regularly used as fertilizers such as ammonium nitrate, ammonium sulfate, sodium nitrate, and urea also triggered siderophore production in S. scabiei. The observed effect is not mediated by alkalinization of the medium as increasing the pH without providing additional nitrogen sources did not induce siderophore production. The nitrogen-induced siderophore production also inhibited the growth of important plant pathogens. Overall, our work suggests that not only the iron availability but also the nitrogen fertilizer sources could significantly impact the competition for iron between crop-colonizing microorganisms.

Iron (Fe) and Zinc (Zn) are essential micronutrients for plant growth and development. ZIP (ZRT, IRT-like protein) transporters, known for their role in the regulation of Zinc and Iron uptake, are pivotal in facilitating the absorption, transport, and maintenance of Fe/Zn homeostasis in plants. Nicotiana tabacum has been widely used as a model plant for gene function analysis; however, the tobacco ZIP genes have not been identified systematically. In this study, we have identified a comprehensive set of 32 NtZIP genes, which were phylogenetically categorized into three distinct clades. The gene structures, characterized by their exon/intron organization, and the protein motifs are relatively conserved, particularly among genes within the same clade. These NtZIP genes exhibit an uneven distribution across 12 chromosomes. The gene localization analysis revealed the presence of 11 pairs of homeologous locus genes and 7 pairs of tandem duplication genes within the genome. To further explore the functionality of these genes, real-time quantitative reverse transcription PCR was employed to assess their expression levels in roots subjected to metal deficiency. The results indicated that certain NtZIP genes are specifically upregulated in response to either Fe or Zn deficiency. Additionally, the presence of specific cis-elements within their promoter regions, such as the E-box associated with Fe deficiency response and the ZDRE box linked to Zn deficiency response, was identified. This study lays a foundational groundwork for future research into the biological functions of NtZIP genes in tobacco in micronutrient regulation and homeostasis.