| Abstract: | SYNOPSIS. Continuous growth of one cell line (UCI variant) of Leishmania tarentolae was achieved in the absence of organic sulfur. These cells were able to use sodium sulfate, and, to a limited extent, sodium sulfite as their sole sulfur source and could utilize methionine sulfoxide in place of L-methionine. A related cell line (RU variant) was unable to grow in organic sulfate-free media nor could these cells utilize methionine sulfoxide. UCI promastigotes incorporated significant amounts of 35S sodium sulfate; killed cells did not take up the label. 35S incorporation was inhibited by sodium molybdate (5 × 10?4 M), sodium arsenite (5 × 10?4 M), 2,4-dinitrophenol (1 × 10?4 M), or KCN (5 × 10?4 M). RU promastigotes did not incorporate significant amounts of 35S sodium sulfate. Thin layer chromatographs of protein hydrolysates from UCI cells incubated in 35S sodium sulfate revealed several radio opaque spots, one of which had chromatographic properties of cystine. UCI variants of L. tarentolae were therefore capable of assimilatory sulfate reduction whereas RU cells lacked this ability. |
