What this entity is
Canonical name: Iron. Known alias: Fe. Stable external identifier: No stable external identifier is reported in the source documents. 1,2
Iron is a metal condition analyzed in gene-level fitness experiments across diverse bacteria. 1 It is related to zinc, cobalt, and copper in the study’s cross-resistance analysis. 1
Key facts from the studies
Iron showed strong positive consensus cross-resistance with zinc, with a mean correlation of r = 0.61 across 6 organisms, the strongest association listed in the study. 1 The study reports that 98.1% of gene-level fitness correlations were positive (311/317) across 317 organism-metal pair observations involving 28 organisms and 85 unique metal pairs. 1
The iron-copper association had r = 0.45 across 7 organisms, while the iron-cobalt association also had r = 0.45 across 7 organisms. 1 These results support the study’s broader finding that cross-resistance has a universal positive directional layer, while the magnitude of associations varies with metal chemistry. 1
The report identifies shared cellular processes—including protein stability, DNA integrity, membrane function, and cofactor insertion—as possible contributors to the common positive direction of metal cross-resistance. 1 This interpretation remains subject to the study’s caveat that no non-metal stress controls were tested, so the analysis cannot distinguish universal metal cross-resistance from a general-stress response to all metals. 1
The Pan-Bacterial Metal Fitness Atlas refines this cross-resistance picture by separating broadly required iron-stress functions from specialized resistance genes: it identified 651 iron-important genes with a 0.919 core fraction, a +0.116 core-fraction delta, OR = 3.07, and p = 8.5e-18. 2 Iron therefore showed stronger core-genome enrichment than the atlas’s toxic-metal pattern, consistent with essential-metal stress exposing vulnerabilities in conserved cellular functions rather than only accessory resistance mechanisms. 2 Iron produced 12.3% important genes in the atlas, although iron had cross-species coverage in only 3 organisms, so this comparison has limited coverage. 2
The metal-specificity analysis refines this atlas result by classifying 144/659 (21.9%) iron-important gene records as metal-specific—the lowest metal-specific fraction reported among the metals tested—using fitness defects under metal experiments and a <5% sick rate across non-metal experiments. 3 Thus, the new analysis supports the interpretation that iron responses include broadly required functions, while indicating that a smaller fraction is specifically attributable to iron stress rather than broader stress sensitivity. 3
Related synthesis
Iron contributes evidence to metal-cross-resistance, which synthesizes conserved positive cross-metal fitness correlations and chemistry-dependent association magnitudes. 1 The atlas supports this synthesis by showing that iron fitness defects are also enriched among conserved core genes, while refining it with the distinction between general metal-sensitive functions and specialized accessory resistance. 2 The metal-specificity analysis further refines the distinction by quantifying the relatively small iron-specific subset and comparing it with non-metal fitness defects. 3 Iron also contributes to cofitness-network-architecture, because gene-level fitness correlations across iron and other metal conditions reveal shared structure across conditions. 1
The underlying reports are Gene-Resolution Metal Cross-Resistance Across Diverse Bacteria, Pan-Bacterial Metal Fitness Atlas, and Metal-Specific vs General Stress Genes. 1,2,3