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Front. Microbiol. | doi: 10.3389/fmicb.2019.02677

Ni(II) interactions in boreal Peanibacillus sp., Methylobacterium sp., Paraburkholderia sp. and Pseudomonas sp. strains isolated from an acidic, ombrotrophic bog

  • 1Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Helsinki, Finland
  • 2VTT Technical Research Centre of Finland Ltd, Finland

The uptake of nickel (Ni(II)) by Peanibacillus sp., Methylobacterium sp., Paraburkholderia sp. and Pseudomonas sp. strains isolated from a boreal bog was studied using batch experiments. All strains removed Ni(II) from the solution and the uptake efficiency was affected by the nutrient source, incubation temperature, time and pH. As highest Ni uptake (with a maximum Kd of 1890 L/kg DW) was recorded for the Pseudomonas sp. strains, these bacteria were used in the following protein expression (SDS-PAGE and MALDI-TOFF), TEM and EDS experiments. In addition, Freundlich and Langmuir sorption isotherms were determined. In the Ni(II) treated cells, dense crystalline intra-cellular accumulations were observed in TEM examinations, which were identified as Ni accumulations using EDS. SDS-PAGE and MALDI-TOFF spectra of Ni(II) treated cells showed several changes in the protein profiles, which can indicate active accumulation of Ni in these bacteria. Concurrently, we observed Ni(II) uptake to follow Freundlich and Langmuir isotherms, suggesting straight cellular biosorption in addition to the intra-cellular accumulation. The role of cellular (cell membrane and cell wall) functional groups involved in Ni(II) binding were therefore studied using Fourier transformation infrared spectroscopy (FTIR). These analyses supported the potential role of the alcoholic hydroxyl, carboxyl and amine groups in Ni(II) binding in these bacteria, therefore suggesting two different Ni(II) uptake mechanisms; (i) intra-cellular accumulation (possibly connected to detoxification of Ni(II)), and (ii) straight biosorption on cell membrane/wall functional groups.

Keywords: Nickel uptake, Adsorption, Sphagnum peat, Heavy metal contamination, Biopurification

Received: 18 Feb 2019; Accepted: 04 Nov 2019.

Copyright: © 2019 Knuutinen, Bomberg, Kemell and Lusa. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Ms. Jenna Knuutinen, Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Helsinki, Helsinki, Finland, jenna.knuutinen@helsinki.fi