Nickel exocellular

Solubility of Exocellular Nickel Complexes in the Soil. To evaluate the effect of microbial metabolites on Ni solubility in soil, the soluble exocellular solution, separated after growth of the 20 selected bacterial isolates and all fungal isolates, was eluted through a column of soil. The concentrations and forms of Ni in the eluates were compared to the concentrations and forms of Ni in water and in the growth medium before and after microbial growth. A column (0.8 x 4 cm) was packed (1.5 g/cc) with sieved (<2 mm), air-dry Ritzville silt loam (1.0 g) and an aliquot of the filtered (<0.4 M<) exocellular medium (2 ml) was eluted through the soil. After 1 ml of eluant was collected, the Ni concentration was determined from the concentration of radio-tracer. Metal form was characterized in soil eluates by TLC and TLE as previously described. 

Modification of Nickel Form by Soil Microbial Isolates. Following isolation from soil and in conjunction with taxonomic characterization, pure cultures of bacteria and fungi were grown to stationary phase in the presence of Ni at several concentration levels. The exocellular solution from each culture was separated by filtration (<0.4 and <0.01 jl) and the Ni-associated components characterized using TLC and TLE. 

Organism Number of Isolates Isolates Modifying Nickel Form Categories of Exocellular Complexes (TLC, TLE)... 

Solubility of Exocellular Nickel Complexes in Soil. To identify those complexes most important in mobilizing Ni in soil, the filtrates (<0.01) of the exocellular media from 20 representative bacterial cultures and all fungal cultures were passed through a column of the soil from which the organisms were isolated and the solubility, and chromatographic and electrophoretic properties of Ni in sterile water, sterile medium and exocellular medium were compared before and after elution through soil. 

Figure 1. Thin-layer chromatographic behavior of nickel complexes with exocellular fungal metabolites (a) before and (b) after elution through soil. Nickel was visualized by autoradiography intensity is directly related to nickel concentration.

Figure 4. Separation by gel permeation chromatography (Sephadex G 25) of exocellular nickel and organic carbon after fungal groioth (isolate 458, 10 fig Ni/mL)...

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