Isolation and identification of a bacterium with high tolerance to lead and copper from a marine microbial mat in Spain

A bacterial strain (DE2008) was isolated from a consortium of microorganisms living in the microbial mats of the Ebro Delta with the ability to grow under conditions of high concentrations of lead and copper. Strain DE2008 has been characterized by microscopic and metabolic techniques and identified by sequencing of PCR-amplified 16S rRNA gene fragments as Micrococcus luteus. The strain is highly resistant to lead and copper. Micrococcus luteus DE2008 grew optimally until levels of 1 mM of Pb(NO₃)₂ and CuSO₄, respectively, and was completely inhibited at 3 mM Pb(NO ₃)₂ and at 1.5 mM CuSO₄. Elemental analysis determined by energy-dispersive X-ray spectroscopy (EDX) coupled with scanning electron microscopy and transmission electron microscopy from polluted cultures of DE2008 show that this microorganism can biosorpt Pb and Cu in exopolysaccharide envelopes, without accumulating them inside the cells.