Siderophore-mediated iron removal from chrysotile: Implications for asbestos toxicity reduction and bioremediation

Abstract

Asbestos fibers are highly toxic (Group 1 carcinogen) due to their high aspect ratio, durability, and the presence of iron. In nature, plants, fungi, and microorganisms release exudates, which can alter the physical and chemical properties of soil minerals including asbestos minerals. We examined whether exudates from bacteria and fungi at environmentally relevant concentrations can alter chrysotile, the most widely used asbestos mineral, and lower its toxicity. We monitored the release of iron from chrysotile in the presence of organic acid ligands and iron-specific siderophores derived from bacteria and fungi and measured any change in fiber toxicity toward peritoneal macrophages harvested from mice. Both fungal and bacterial siderophores increased the removal of iron from asbestos fibers. In contrast, organic acid ligands at environmentally relevant concentrations neither released iron from fibers nor helped in siderophore-mediated iron removal. Removal of plant-available or exchangeable iron did not diminish iron dissolution by both types of siderophores, which indicates that siderophores can effectively remove structural iron from chrysotile fibers. Removal of iron by siderophore lowered the fiber toxicity; fungal siderophore appears to be more effective than bacterial siderophore in lowering the toxicity. These results indicate that prolonged exposure to siderophores, not organic acids, in the soil environment decreases asbestos fiber toxicity and possibly lowers the health risks. Thus, bioremediation should be explored as a viable strategy to manage asbestos-contaminated sites such as Brownfield sites, which are currently left untreated despite dangers to surrounding communities.

Laser ablation inductively coupled plasma mass spectrometry as a novel clinical imaging tool to detect asbestos fibres in malignant mesothelioma

“…The parameters were optimised for maximum 24 Mg, 29 Si, 57 Fe ion sensitivity, while ensuring that individual pulse responses could be resolved at the stated repetition frequency. These elements were imaged separately, due to the slow scanning speed of the ICP-MS instrument compared with the fast response of the laser ablation system.…”

“…B The relatively high 24 Mg intensity signal in the fibres visible in microscope images, as well as smaller fragments within the cell layer that could not be seen initially. C, Similarly, the 29 also used as a matrix (data not presented). There was no significant difference in either 24 Mg, 57 Fe or 29 Si intensity signals generated by the two cellular models.…”

“…C, Similarly, the 29 also used as a matrix (data not presented). There was no significant difference in either 24 Mg, 57 Fe or 29 Si intensity signals generated by the two cellular models. The elemental intensity generated by the NCI-H28 cells is presented in Figures 1A-1C.…”

“…Note that the engulfed amosite fibres are not visible in the microscopic image. C, 29 Si distribution within the matrix and amosite fibres [Color figure can be viewed at wileyonlinelibrary.com] intensity generated by 24 Mg (Figure 1B), present at detectable and relatively homogeneous levels within the biological matrix, making it a suitable choice to aid correlation of the LA-ICP-MS and microscopic images.…”

Framework for assessment and phytoremediation of asbestos-contaminated sites

“…Plants are known to stabilize the topsoil and minimize erosion (Alkorta et al 2010; Brown and Chaney 2016), which could limit asbestos exposure via air. Furthermore, recent laboratory studies show that organic acids typically released from plant roots or soil microbe can leach out elements, alter surface charge of fibers, and induce a lower toxicity (Daghino et al 2006; Favero-Longo et al 2013; Holmes and Lavkulich 2014; Mohanty et al 2017). Thus, phytostabilization and phytoremediation, more broadly, could be viable technology for asbestos-contaminated sites.…”