Daisley et al. 2018 - Lactobacillus sequestration of lead and cadmium

Daisley and colleagues tested whether Lactobacillus rhamnosus GR-1 and related lactobacilli can bind lead and cadmium in solution and reduce transport across an intestinal epithelial model. This is probiotic mitigation evidence: it supports a sequestration mechanism for reducing absorption from contaminated food or water, but it does not measure metals in probiotic supplements or consumer foods.

Key numbers

In vitro binding

The source reports that L. rhamnosus GR-1, L. plantarum 14917T, and L. casei 393T significantly reduced Pb and Cd in solution across the tested concentration range. Figure 1 tested Pb at 0.5, 2.0, and 50 mg/L and Cd at 0.5, 2.5, and 50 mg/L, with all experiments performed from 3 independent experiments and analyzed in triplicate.

For L. rhamnosus GR-1, relative Pb binding was higher at 0.5 mg/L than at 50 mg/L:

For cross-species comparison at lower concentrations, E. coli Co1 and E. coli 25922 significantly reduced Cd in solution at 1 mg/L, binding 72.41 +/- 5.91% and 71.43 +/- 3.94%, respectively, but neither E. coli strain significantly reduced Pb.

Binding kinetics and viability

The authors monitored Pb and Cd binding over 48 hours. Minimal change in bound Pb or Cd was observed from 15 minutes to 48 hours for L. rhamnosus GR-1 and L. plantarum 14917T. Heat-killed L. rhamnosus GR-1 did not differ significantly from live L. rhamnosus GR-1 for Pb or Cd binding, with p = 0.5654 for Pb and p = 0.9948 for Cd, supporting a passive binding mechanism.

Microscopy and translocation model

SEM and energy-dispersive X-ray analysis confirmed Pb and Cd on metal-treated bacterial samples. Pb appeared as irregular cell-surface clusters on L. rhamnosus GR-1, while Cd appeared as intracellular dense precipitates in TEM images.

In a Caco-2 Transwell model, L. rhamnosus GR-1 significantly increased Pb remaining in the apical compartment compared with vehicle controls (two-way ANOVA, p = 0.0354) and significantly reduced Pb appearing in the basolateral chamber after 5 hours (two-way ANOVA, p = 0.0400). Cd in the basolateral chamber was also significantly reduced with L. rhamnosus GR-1 treatment compared with vehicle controls (two-way ANOVA, p = 0.0104).

Methods (brief)

Overnight bacterial cultures were grown, washed, and used at a final concentration of 10^9 CFU/mL. For solution-binding assays, bacterial pellets were suspended in 5 mL of 50 mM HEPES buffer at pH 7.0 containing Pb or Cd, incubated from 5 minutes to 48 hours at 37 degrees C with gentle shaking, centrifuged, and the supernatant was preserved with ultrapure nitric acid.

Pb and Cd were quantified by ICP-AES using EPA method 6010 calibration standards from 0.05 to 5.0 mg/L. The method detection limit for both Pb and Cd was 0.01 mg/L. Caco-2 Transwell inserts were grown to confluent monolayers, treated with metals with or without L. rhamnosus GR-1, and apical/basolateral metal compartments were measured after the exposure interval.

Implications

Certification: Do not use this source in product occurrence pools for probiotics, supplements, foods, or drinking water. It measures in vitro sequestration and cell-model translocation, not market-product contamination.

App: Useful context for mitigation explainers where probiotic strains may reduce gastrointestinal absorption of Pb or Cd from contaminated diets.

Courses: Useful example for distinguishing a consumer-product category name from a mitigation mechanism: the probiotic strain is the intervention, not a sampled supplement with contaminant concentrations.

Wiki pages this source may touch

• formulation
• remediation-evidence
• lead
• cadmium
• index

Verification notes

This page was built from the full PDF text, including the abstract, Results sections for Figures 1-4, and Methods sections for heavy-metal quantification and Caco-2 translocation. Products and ingredients are intentionally empty because all numeric values are spiked-solution, bacterial-binding, or epithelial-model values. The source names Lactobacillus strains and E. coli laboratory strains; these are biological materials and methods, not consumer brands.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.