Ralstonia

Ralstonia is a genus of Gram-negative, aerobic bacteria in the class Betaproteobacteria. While Wikipedia focuses on R. solanacearum (a plant pathogen), the WikiBiome-relevant species are R. pickettii and R. metallidurans (now Cupriavidus metallidurans) — organisms with extreme multi-metal tolerance that appear in human gut microbiome studies, particularly in metal-exposed populations.

Metal Resistance — The CzcCBA Paradigm

R. metallidurans is the reference organism for bacterial heavy metal resistance, harboring the CzcCBA efflux system — the best-characterized multi-metal efflux pump in biology:

  • CzcCBA exports cobalt, cadmium, zinc, and nickel, conferring survival in heavily contaminated environments [1].
  • This efflux system is the prototype for co-selection: the same CzcCBA operon that confers metal tolerance also provides resistance to multiple antibiotics, demonstrating how environmental metal pollution drives antibiotic resistance [1].

Cadmium-Responsive Enrichment

Ralstonia abundance increases in response to cadmium exposure in animal models:

  • Enriched in the gut microbiota of cadmium-exposed rats, consistent with its metal tolerance providing a selective advantage when competing organisms are inhibited by cadmium [2] [3].
  • The enrichment pattern suggests Ralstonia as a potential biomarker of environmental metal exposure in gut microbiome profiling.

Disease Associations

  • CKD: Enriched in gut microbiota of CKD patients, where uremic toxin accumulation creates a metal-dysregulated environment [4].
  • ASD: Altered in gut microbiota of constipated ASD children [5].
  • Infant metal exposure: Ralstonia abundance correlates with infant serum metal levels, suggesting early-life metal exposure shapes Ralstonia colonization [6].
  • PCOS: Present in vaginal microbiome of PCOS patients [7].
  • Diabetes/MI: Part of gut microbiome shifts in diabetes with myocardial infarction [8].

Cross-References

References (9)

  1. Srivastava J, Chandra H, Singh N et al. (2016). Understanding the Development of Environmental Resistance Among Microbes: A Review. Clean - Soil, Air, Water. doi:10.1002/clen.201300975
  2. Liu S, Deng X, Li Z et al. (2023). Liu 2023 — Environmental cadmium exposure alters the internal microbiota and metabolome of Sprague–Dawley rats. Frontiers in Veterinary Science. doi:10.3389/fvets.2023.1219729
  3. Songqing Liu, Xin Deng, Zheng Li et al. (2023). Environmental cadmium exposure alters the internal microbiota and metabolome of Sprague-Dawley rats. Frontiers in Veterinary Science. doi:10.3389/fvets.2023.1219729
  4. Wu Liu, Jiaqi Huang, Tong Liu et al. (2023). Liu 2023 — Changes in Gut Microbial Community upon Chronic Kidney Disease. PLOS ONE. doi:10.1371/journal.pone.0283389
  5. Jianquan He, Xiuhua Gong, Bing Hu et al. (2023). He 2023 — Altered Gut Microbiota and Short-Chain Fatty Acids in Chinese Children with Constipated Autism Spectrum Disorder. Scientific Reports. doi:10.1038/s41598-023-46566-2
  6. Xing Yan, Jun Qiu, Ruiwen Huang et al. (2025). Yan 2025 — Association Between Infants' Serum Levels of 26 Metals and Gut Microbiota: A Hospital-Based Cross-Sectional Study in China. Frontiers in Microbiology. doi:10.3389/fmicb.2025.1669475
  7. Zheng S, Chen H, Yang H et al. (2024). Zheng 2024 — Differential enrichment of bacteria and phages in vaginal microbiomes in PCOS and obesity: shotgun sequencing analysis. Frontiers in Microbiomes. doi:10.3389/frmbi.2023.1229723
  8. Honghong Zhang, Changlin Zhai, Huilin Hu et al. (2026). A metagenomic study of the gut microbiome in patients with type 2 diabetes mellitus and myocardial infarction. Acta Diabetologica. doi:10.1007/s00592-026-02648-x
  9. Filipe T. Lira Neto, Marina C. Viana, Federica Cariati et al. (2024). Neto 2024 — Effect of Environmental Factors on Seminal Microbiome and Impact on Sperm Quality. Frontiers in Endocrinology. doi:10.3389/fendo.2024.1348186

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