Cellular strategies against metal exposure and metal localization patterns linked to phosphorus pathways in Ochrobactrum anthropi DE2010

Abstract

Cytotoxic, chemical, biochemical, compositional, and morphometric responses were analyzed against heavy metal exposure in Ochrobactrum anthropi DE2010, an heterotrophic bacterium isolated from Ebro Delta microbial mats (Tarragona, NE Spain). Several parameters of effect and exposure were evaluated to determine tolerance to a range of cadmium (Cd), lead (Pb(II)), copper (Cu(II)), chromium (Cr(III)), and zinc (Zn) concentrations. Additionally, removal efficiency, polyphosphate production and metal localization patterns were also analyzed. O. anthropi DE2010 showed high resistance to the tested metals, supporting concentrations of up to 20 mM for Zn and 10 mM for the rest of the elements. The bacterium also demonstrated a high removal capacity of metals-up to 90 % and 40 % for Pb(II) and Cr(III), respectively. Moreover, polyphosphate production was strongly correlated with heavy metal concentration, and three clear cell localization patterns of metals were evidenced using compositional and imaging techniques: (i) extracellular in polyphosphate granules for Cu(II); (ii) in periplasmic space forming crystals with phosphorus for Pb(II); and (iii) intracytoplasmic in polyphosphate inclusions for Pb(II), Cr(III), and Zn. The high resistance and metal sequestration capacity of O. anthropi DE2010 both highlight its great potential for bioremediation strategies, especially in Pb and Cr polluted areas.

Keywords: Bioaccumulation; Biomineralization; Heavy metal; Polyphosphate production; Sequestration.