GROWTH-CHARACTERISTICS AND ARSENIC METABOLISM OF 2 SPECIES OF ARSENIC-TOLERANT BACTERIA

Two arsenic‐tolerant bacterial species were isolated from a contaminated culture of the alga Chlorella sp. One of the bacterial species was identified as Pseudomonas putida; both were aerobic heterotrophs. The bacteria grew well in a peptone medium of neutral pH at room temperature and reached the stationary phase in approximately four days. Growth was not impaired by arsenic concentration as high as 1000 mg dm−3 As in the form of arsenate, but decreased drastically at higher concentrations. P. putida grown in a peptone medium with 10 mg dm−3 As as arsenate, reached a maximal arsenic concentration of 67 mg kg−1 (dry mass) after 48 h of growth in the late log phase. Most of the arsenic in the cells was inorganic and 3% of the arsenic was in the trimethylated form. During the stationary phase the bacteria excreted arsenic largely in the inorganic, but also in the inorganic, but also in the mono‐, di‐, and trimethylated, forms. Copyright © 1990 John Wiley & Sons Ltd.