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Abstract:
Biomineralization by heavy metal-resistant streptomycetes was tested to evaluate the potential influence
on metal mobilities in soil. Thus, we designed an experiment
adopting conditions from classical laboratory methods
to natural conditions prevailing in metal-rich soils with
media spiked with heavy metals, soil agar, and nutrientenriched
or unamended soil incubated with the bacteria.
As a result, all strains were able to form struvite minerals
(MgNH4PO4
6H2O) on tryptic soy broth (TSB)-media
supplemented with AlCl3, MnCl2 and CuSO4, as well as
on soil agar. Some strains additionally formed struvite on
nutrient-enriched contaminated and control soil, as well as on
metal contaminated soil without addition of media components.
In contrast, switzerite (Mn3(PO4)2
7H2O) was exclusively
formed on minimal media spiked with MnCl2 by four
heavy metal-resistant strains, and on nutrient-enriched control
soil by one strain. Hydrated nickel hydrogen phosphate
was only crystallized on complex media supplemented with
NiSO4 by most strains. Thus, mineralization is a dominant
property of streptomycetes, with different processes likely
to occur under laboratory conditions and sub-natural to natural
conditions. This new understanding might have implications
for our understanding of biological metal resistance
mechanisms. We assume that biogeochemical cycles, nutrient
storage and metal resistance might be affected by formation
and re-solubilization of minerals like struvite in soil at
microscale.
