Tolerance to and Accumulation of Cadmium, Copper, and Zinc by Cupriavidus necator

Abstract

Preliminary results of in vitro experiments with multicontaminated soils and solid media indicated that nodulating diazotrophic bacteria of the genus Cupriavidus are promising for the remediation of contaminated environments due to their symbiosis with legumes and metal tolerance. Thus, strains of Cupriavidus spp. (LMG 19424 T , UFLA 01-659, UFLA 01-663, and UFLA 02-71) were tested for their ability to tolerate and bioaccumulate cadmium (Cd), copper (Cu), and zinc (Zn) in Luria-Bertani broth. Changes in the growth pattern of Cupriavidus strains in the presence or absence of heavy metals were analyzed by scanning electron microscopy and metal allocation by transmission electron microscopy, to clarify the mechanisms of bioremediation. Highest tolerance was detected for strain UFLA 01-659 (minimum inhibitory concentration of 5, 4.95, and 14.66 mmol L -1 of Cd, Cu, and Zn, respectively). Among the removal rates of the metals tested (9.0, 4.6, and 3.2 mg L -1 of Cd, Cu, and Zn, respectively), the bacterial activity was clearly highest for Cd. The efficiency of strain UFLA 01-659 in removing the heavy metals is associated with its high biomass production and/or higher contents of heavy metals adsorbed and absorbed in the biomass. In response to the presence of heavy metals in the liquid culture medium, the bacteria produced exopolysaccharides and small and aggregated cells. However, these responses varied according to the strains and heavy metals. Regarding allocation, all heavy metals were adsorbed on the cell wall and membrane, whereas complexation was observed intracellularly and only for Cu and Zn. These results indicate the possibility of using C. necator UFLA 01-659 for remediation in areas with very high Cd, Cu, and Zn contents.

Indigenous multiresistant bacteria of Cupriavidus pauculus IrC4 isolated from Indonesia as a heavy metal bioremediation agent

“…This result was supported by the result of Vicentin et al (2018) that there were differences between bacterial growth in medium containing copper, cadmium, mercury, and lead compared to bacterial growth in medium without heavy metals. A high concentration of heavy metals inhibited the growth of bacteria.…”

“…Cupriavidus alkaliphilus grow effectively in the presence of arsenic, copper, and zinc. Cupriavidus necator can remove cadmium, zinc, and copper from contaminated soil (Vicentin et al 2018). Inoculation of this strain increases the ability of Helianthus annuus to deal with heavy metal toxicity when applied as a phytoremediation agent in polluted environments (Santos et al 2014).…”

“…Inoculation of this strain increases the ability of Helianthus annuus to deal with heavy metal toxicity when applied as a phytoremediation agent in polluted environments (Santos et al 2014). Cupriavidus gilardii CR33 has multiple metal resistance to cadmium, zinc, copper, and argentum (Vicentin et al 2018). Cupriavidus taiwanensis strains show a wide range of tolerances to Ni, Zn, and Cr indicating their adaptation to the specific environment in New Caledonia (Klonowska et al 2012).…”

Isolation and characterization of an acid and metal tolerant Enterobacter cloacae NZS strain from former mining lake in Selangor, Malaysia

“…Some species of these genera have been reported to tolerate high concentration of heavy metals. For instance, Stenotrophomonas maltofilia was resistant to high levels of toxic metals including selenite, tellurite, cadmium, lead, cobalt, zinc, silver, and mercury [29]; Cupriavidus necator reportedly showed tolerance and ability to leach cadmium, zinc, and copper from contaminated soils [30] while C. gilardii CR3 removed copper from chemical mechanical polishing (CMP) wastewater at an optimum pH of 5 [31]. Pseudomonas sp., strain DC-B3, was found to be resistant to copper and cadmium [32], and P. protegens strains (S4LiBe and S5LiBe) isolated from an agricultural well near a heavy metal polluted site were reportedly tolerant to 2.0 mM K 2 Cr O7 and 3.0 mM CoSO 4 , HgSO 4 , CdSO 4 .8H 2 O, and PbCl 2 [32].…”

Genomic and Physiological Investigation of Heavy Metal Resistance from Plant Endophytic Methylobacterium radiotolerans MAMP 4754, Isolated from Combretum erythrophyllum

“…As previously discussed by [73], the high resistance of M. radiotolerans MAMP 4754 to heavy metal stress is possibly due to an efficient ion efflux and metal complexation and reduction, and thus self-repair capabilities. It may therefore be inferred that metal allocation within bacterial cells is determined by the mechanism of tolerance for each microorganism [74]. For example, when intracellular sequestration is the method of heavy metal detoxification, the complexation of metal ions occurs in the bacterial cell cytoplasm [75]; extracellular sequestration on the other hand, results in the accumulation of metal ions within the periplasm or the complexation of these heavy metals into less toxic insoluble compounds [75].…”