Internal Transcribed Spacer and 16S Amplicon Sequencing Identifies Microbial Species Associated with Asbestos in New Zealand

Abstract

Inhalation of asbestos fibres can cause lung inflammation and the later development of asbestosis, lung cancer, and mesothelioma, and the use of asbestos is banned in many countries. In most countries, large amounts of asbestos exists within building stock, buried in landfills, and in contaminated soil. Mechanical, thermal, and chemical treatment options do exist, but these are expensive, and they are not effective for contaminated soil, where only small numbers of asbestos fibres may be present in a large volume of soil. Research has been underway for the last 20 years into the potential use of microbial action to remove iron and other metal cations from the surface of asbestos fibres to reduce their toxicity. To access sufficient iron for metabolism, many bacteria and fungi produce organic acids, or iron-chelating siderophores, and in a growing number of experiments these have been found to degrade asbestos fibres in vitro. This paper uses the internal transcribed spacer (ITS) and 16S amplicon sequencing to investigate the fungal and bacterial diversity found on naturally-occurring asbestos minerals, asbestos-containing building materials, and asbestos-contaminated soils with a view to later selectively culturing promising species, screening them for siderophore production, and testing them with asbestos fibres in vitro. After filtering, 895 ITS and 1265 16S amplicon sequencing variants (ASVs) were detected across the 38 samples, corresponding to a range of fungal, bacteria, cyanobacterial, and lichenized fungal species. Samples from Auckland (North Island, New Zealand) asbestos cement, Auckland asbestos-contaminated soils, and raw asbestos rocks from Kahurangi National Park (South Island, New Zealand) were comprised of very different microbial communities. Five of the fungal species detected in this study are known to produce siderophores.

A Preliminary Investigation into the Degradation of Asbestos Fibres in Soils, Rocks and Building Materials Associated with Naturally Occurring Biofilms

“…Asbestos-contaminated soil samples also showed indications of fibril amorphization. Unfortunately, no DNA sequence data were available for these particular samples, but other asbestos-contaminated soil samples from the same areas were sequenced by Doyle et al [38], who identified a range of fungal and bacterial species as being present, including Cladosporium cladosporoides, Epicoccum nigrum, Fusarium oxysporum and Yarrowia lipolytica, all of which have been reported in the literature as being able to produce siderophores in vitro [16,36,39,40]. Previous research by Martino et al [19] found that several soil fungi were able to remove iron from crocidolite fibres in vitro.…”

Siderophore production in fungi from asbestos biofilms: The first step towards bioremediation of a carcinogenic mineral

“…It has been shown that asbestos fibres can be partially degraded, and the surface reactivity reduced, by the activity of some fungi, bacteria and lichens, and that this is due to removal of metal ions, including iron, by siderophores and similar iron-chelating compounds (Bhattacharya et al 2015;Daghino et al 2006;Daghino et al 2008;Daghino et al 2010;Favero-Longo et al 2005;Favero-Longo et al 2007;Mohanty et al 2018). Several studies have shown that a range of bacteria, cyanobacteria, filamentous fungi, yeast fungi and lichenised fungi are able to colonise asbestos and related mineral deposits (Bhattacharya et al 2016;Daghino et al 2008, Daghino et al 2009Doyle et al 2023).…”

“…For microbial bioremediation to be successful, it is necessary to assemble a library of potential siderophore-producing bacteria or fungi that are well suited to the environmental conditions of the local area (Doyle et al 2023). Production of siderophores in candidate isolates can be detected by culturing them on chrome azurol S (CAS)-agar plates.…”