Biomineralization by Extremely Halophilic and Metal-Tolerant Community Members from a Sulfate-Dominated Metal-Rich Environment

Abstract

The adaptation to adverse environmental conditions can lead to adapted microbial communities that may be screened for mechanisms involved in halophily and, in this case, metal tolerance. At a former uranium mining and milling site in Seelingstädt, Germany, microbial communities from surface waters and sediment soils were screened for isolates surviving high salt and metal concentrations. The high salt contents consisted mainly of chloride and sulfate, both in soil and riverbed sediment samples, accompanied by high metal loads with presence of cesium and strontium. The community structure was dominated by Chloroflexi, Proteobacteria and Acidobacteriota, while only at the highest contaminations did Firmicutes and Desulfobacterota reach appreciable percentages in the DNA-based community analysis. The extreme conditions providing high stress were mirrored by low numbers of cultivable strains. Thirty-four extremely halotolerant bacteria (23 Bacillus sp. and another 4 Bacillales, 5 Actinobacteria, and 1 Gamma-Proteobacterium) surviving 25 to 100 mM SrCl2, CsCl, and Cs2SO4 were further analyzed. Mineral formation of strontium- or cesium-struvite could be observed, reducing bioavailability and thereby constituting the dominant metal and salt resistance strategy in this environment.

Extremophile Metal Resistance: Plasmid-Encoded Functions in Streptomyces mirabilis

“…For S. mirabilis P16B-1, struvite (a magnesium-containing ammonium phosphate) or a nickel phosphate had been observed to be formed earlier ( 47 ). In addition, an ammonium phosphate mineral, nickel struvite, had been described to be formed due to metabolic activity and high local metal concentrations surrounding the cells of other metal-resistant strains isolated in the same former mining area ( 3 , 58 ). The same morphology and color observed here indicated that in S. mirabilis , Ni-struvite is the precipitated mineral as well.…”

Salt and Metal Tolerance Involves Formation of Guttation Droplets in Species of the Aspergillus versicolor Complex

“…Isolation of fungal strains was performed with soil samples from a former uranium mining site [ 4 ]. The samples were taken at a location receiving drainage waters from tailings and are specifically rich in Sr and Cs (compare Supplementary Table S1 ) at the former uranium mining and milling site near Seelingstädt, Thuringia, Germany ( Figure 1 ).…”

“…After trimming, demultiplexing, denoising, sequence merging, ASV resolving, and chimera removal, analysis and phylogenetic tree reconstruction were performed as described above, adding correlation analyses tools available with R (version 4.2.0). All sequences are available at NCBI Sequence Read Archive under the Bioproject PRJNA784578 [ 4 ].…”

“…In saline soil, highly specialized microbes adapted to the driving environmental factors occur. With respect to high salt loads such as NaCl or sulfates and radionuclides such as U, Cs and Sr, a potential application for bioremediation is feasible [ 2 , 3 , 4 ]. The former uranium mining and milling site near Seelingstädt, Germany, represents such a site where high metal loads and salt concentrations influence and shape the fungal community [ 4 ].…”

Biomineralization of Nickel Struvite Linked to Metal Resistance in Streptomyces mirabilis

“…Molecular mechanisms in mineral formation are known to occur through the production of nucleation molecules, or by changing environmental conditions on a small scale [ 5 , 6 , 7 , 8 , 9 ]. Different molecules are involved as templates for the nucleation of biominerals [ 10 ], including proteins, lipids, or polysaccharides.…”