Activation of Promutagens by a Unicellular Green Alga

Classic mutagenicity testing includes mammalian activation of promutagens. A relatively new approach to examining environmental mutagens involves the plant activation of promutagens. A plant system was developed using the aquatic unicellular green alga Selenastrum capricornutum as the activating mechanism. The genetic indicator organism used was the Ames strain TA98 of Salmonella typhimurium. Two treatment groups were examined: alga, TA98, and a test chemical incubated together; and TA98 and a test chemical incubated together without the alga. The test chemicals examined were m-phenylenediamine (MPD), aflatoxin B₁, and atrazine. Differences in the number of revertants were compared between the reaction mixtures of the two treatment groups. For MPD and aflatoxin, there was a significant difference between the two treatment groups with the algal treatment group producing a higher number of revertants. There was no effect seen with the atrazine at the concentrations tested or with the TA98 strain. It was shown that the chemically treated alga does not act as an exogenous source of histidine for the TA98. Selenastrum demonstrated a consistent trend of weak activation of the promutagens MPD and aflatoxin B₁.