Use of oligotrophic bacteria for the biological monitoring of heavy metals

摘要

Oligotrophic bacteria exhibited active growth even in nutritionally deficient medium made with nutrient broth that had been diluted with distilled water, 1 : 10 000. The oligotrophic bacteria, Sphingomonas paucimobilis KPS01 and Burkholderia cepacia KPC01 and KPC02 were found to be highly susceptible to heavy metals and to be potentially useful as sensors for the assessment of toxicity. The susceptibility of the bacteria to metals was measured by incubating the bacteria with metals of varying concentrations in the nutritionally deficient medium at 30 deg C for 24 h. Bacteria were considered susceptible when the growth inhibition rate (EC_(50)) was more than 50% of the control. The EC_(50) value of Ag~+, Pb~(2+) and Cd~(2+) was 10~(-5) mmol l~(-1) and Zn~(2+), Cr~(3+), Cr~(6+), Cu~(2+) and Hg~(2+) was 10~(-4) mmol l~(-1) in S. paucimobilis KPS01. Other strains also showed similar results. No difference in the EC_(50) was found using either the chloride or sulphate forms of these metals. The optimum incubation time was 24 h and a longer incubation time did not necessarily lead to more inhibition. The EC_(50) value rose in proportion to the concentration of nutrition in media. Environmental samples were tested and 14 out of 88 samples inhibited the growth of S. paucimobilis KPS01.