How to Cope With Heavy Metal Ions: Cellular and Proteome-Level Stress Response to Divalent Copper and Nickel in Halobacterium salinarum R1 Planktonic and Biofilm Cells
Halobacterium salinarum R1 is an extremely halophilic archaeon capable of adhesion
and forming biofilms, allowing it to adjust to a range of growth conditions. We have
recently shown that living in biofilms facilitates its survival under Cu2+ and Ni2+ stress,
with specific rearrangements of the biofilm architecture observed following exposition.
In this study, quantitative analyses were performed by SWATH mass spectrometry to
determine the respective proteomes of planktonic and biofilm cells after exposition to
Cu2+ and Ni2+.Quantitative data for 1180 proteins were obtained, corresponding to
46% of the predicted proteome. In planktonic cells, 234 of 1180 proteins showed
significant abundance changes after metal ion treatment, of which 47% occurred in
Cu2+ and Ni2+ treated samples. In biofilms, significant changes were detected for 52
proteins. Only three proteins changed under both conditions, suggesting metal-specific
stress responses in biofilms. Deletion strains were generated to assess the potential
role of selected target genes. Strongest effects were observed for 1OE5245F and
1OE2816F strains which exhibited increased and decreased biofilm mass after Ni2+
exposure, respectively. Moreover, EPS obviously plays a crucial role in H. salinarum
metal ion resistance. Further efforts are required to elucidate the molecular basis and
interplay of additional resistance mechanisms