Biodeterioration of asbestos cement by siderophore-producing Pseudomonas

Abstract

Since the ban on the use of asbestos due to its carcinogenic properties, the removal of asbestos cement, representing the major asbestos-containing waste, has proven to be a challenge in most industrial countries. Asbestos-containing products are mainly disposed of in landfills and have remained untreated. Bioremediation involving bacteria previously reported the ability of Pseudomonas aeruginosa to release iron from flocking asbestos waste through a siderophore-driven mechanism. We examined the involvement of siderophore-producing Pseudomonas in the biodeterioration of asbestos cement. Iron and magnesium solubilization were evaluated by specific siderophore-producing mutants. The absence of one of the two siderophores affected iron extraction, whereas equivalent dissolution as that of the control was observed in the absence of siderophore. Both pyoverdine and pyochelin biosynthesis was repressed in the presence of asbestos cement, suggesting iron bioavailability from the waste.We compared the efficiency of various pyoverdines to scavenge iron from asbestos cement waste that revealed the efficiency of all pyoverdines. Pyoverdines were efficient in iron Revised Manuscript Texte removal extracted continuously, with no evident extraction limit, in long-term weathering experiments with these pyoverdines. The optimization of pyoverdine-asbestos weathering may allow the development of a bioremediation process to avoid the disposal of such waste in landfills.

A Review of Asbestos Bioweathering by Siderophore-Producing Pseudomonas: A Potential Strategy of Bioremediation

“…Recently, studies of David et al [72,[78][79][80] corroborate that these siderophores are also involved in the dissolution of other silicate minerals such as asbestiform minerals. Indeed, asbestos is an iron source for various microorganisms.…”

“…On the other hand, direct evidence of iron weathering from asbestos by siderophore was shown with deferoxamine [18,85], EDTA [78,85] or citrate [85]. However, it is only recently that the direct implication of siderophore in the dissolution of raw asbestos and ACW was demonstrated by the use of siderophore mutants and fluorescent protein labeling [78][79][80]. First, asbestos bioweathering by siderophore-producing Pseudomonas was demonstrated with direct evidence of iron removal by PVD (Figure 3).…”

“…Siderophores and organic acids have already been shown to function synergistically in mineral dissolution [48]. The influence of organic acids in chrysotile dissolution is also a hypothetical process, given that bacterial growth is not affected by the absence of PVD and PCH, concluding of a sufficient iron dissolution [79,80]. In addition, Pseudomonas are also well-recognized to colonize minerals via a biofilm formation.…”

“…Recently, David et al [72,80] investigated the efficiency of various PVDs to scavenge iron from ACW. According to materials, the more efficient PVDs to extract iron are different ( Figure 6).…”

“…However, given PVDs share the same ligand groups, the affinity constant might not be sufficiently different to explain the differences according to ACW. Indeed, David et al [80] hypothesized that the various 3D structures between PVDs might be the influencing parameter of iron extraction ability. Thus, some structures could more easily access the structural iron present in the layers of chrysotile.…”