Microbial Sensor for Preliminary Screening of Mutagens

Abstract

The recombination of deficient strain B. subtilis M45 Rec− and the wild strain B. subtilis H17 Rec+ were employed for developing a sensor for testing for mutagens (1–4). Immobilization of the bacteria was8performed by dropping a bacteria suspension containing 2.7 × 108 cells onto a porous acetylcellulose membrane (Millipore, Type HA, 0.45 µm pore size) with slight suction. The microbial sensor system consisted of two microbial electrodes: a) an electrode of B. subtilis Rec+ (Rec+ electrode) and b) an electrode of B. subtilis_Rec+ (Rec+ electrode) plus two oxygen electrodes. When the Rec− and Rec+ electrodes were inserted into 0.3 g/L buffered glucose solution, steady-state currents were obtained. Then, the mutagen 2-(2-furyl)-3-(5-nitro-2-furyl) acrylamide (AF2) was added. The time course of electrode current is shown in Pig. 1. The rate of current increase was a measure of the mutagen concentration and was most easily measured as the linear slope at the midpoint of the sig-moidal curve. When chemical mutagens, such as AF-2, mitomycin, captan, 4-nitroquinoline-N-oxide, N-methyl-N’-nitro-N-nitroso-guanidine, aflatoxin B, 2-aminoanthracene, and 2-acetylaminofluorene, were added to the glucose-buffer solution, the currents of the Rec− electrode increased markedly; and the mutagenicity of these chemicals could be estimated with the electrochemical system.