Ecological selection of siderophore-producing microbial taxa in response to heavy metal contamination

Some microbial public goods can provide both individual and community‐wide benefits, and are open to exploitation by non‐producing species. One such example is the production of metal‐detoxifying siderophores. Here, we investigate whether conflicting selection pressures on siderophore production by heavy metals – a detoxifying effect of siderophores, and exploitation of this detoxifying effect – result in a net increase or decrease. We show that the proportion of siderophore‐producing taxa increases along a natural heavy metal gradient. A causal link between metal contamination and siderophore production was subsequently demonstrated in a microcosm experiment in compost, in which we observed changes in community composition towards taxa that produce relatively more siderophores following copper contamination. We confirmed the selective benefit of siderophores by showing that taxa producing large amounts of siderophore suffered less growth inhibition in toxic copper. Our results suggest that ecological selection will favour siderophore‐mediated decontamination, with important consequences for potential remediation strategies

Prediction of leachate quality for a gossan dump, Angostura, Spain

The Iberian Pyrite Belt (IPB) is one of the largest of the world’s massive sulfide provinces. Since the Chalcolithic era, gossans formed from massive sulfide mineralization have been worked for copper, silver and gold. Consequently many historical mine sites have abandoned dumps of gossanous material. One such example is located at Angostura, a historical copper mine which operated from 1906 to 1931. The aims of this study are to determine the mineralogical hosts of environmentally significant elements (As, Ba, Bi, Co, Cu, Hg, Mo, Sb, Se, Ni, Pb, Zn) in gossanous waste rocks dumped adjacent to the Angostura open cut, using geochemical, optical, SEM-MLA and laser ablation techniques. Our findings demonstrate that the gossan materials are enriched in environmentally significant elements with several hosted by iron oxides and iron-oxyhydroxides. Leaching of these gossan materials was performed using three extractants to represent different conditions which may be experienced in a surficial environment (i.e., deionized water, hydrogen peroxide and sulfuric acid). Results from these experiments indicated that under ambient surface conditions all analyzed elements will not be released from their goethite and hematite hosts. However, under ARD conditions, elements such Co, Cu, Pb and Zn will be mobilized

The effect of lime addtion on microbial siderophore production in polluted soil communities

The first data sheet in this Excel file contains a brief description of the study locations as well as data quantifying the effect of lime addition on changes in soil pH measured over a time frame of 12 weeks. The second data sheet provides information about the availability of 16 heavy metals in limed and control soil microbial communities. The third data sheet provides information about siderophore production (measured using liquid CAS assays) of 24 clones per unique community and across three different selection regimes (natural, lime and control soil communitie