[A study of the action of sodium chlorate on strains of nitrate reducing soil bacteria (author's transl)].

Fours strains of nitrate reducing bacteria isolated from soil were studied for their behavior towards chlorate. They are facultative anaerobes, except for Bacillus megatherium (which is a strict aerobe) and they possess a nitrate reductase A. The growth of three strains of bacteria (Klebsiella pneumoniae, B. licheniformis and Micromonospora globosa) was slowed by sodium chlorate at a concentration of 0.06 to 0.1% while the other strain (B. megatherium) tolerated the CIO3- well. The delay of bacterial growth due to chlorate lasts for a certain period, after which the bacteria multiply again. The lag phase is due to small quantities of chlorite produced from the chlorate; the growth phase which follows is provoked by the multiplication of chlorate resistant mutants, most often nitrate reductase-negative and sometimes positive. Some reverse mutants nitrate reductase positive of K. pneumoniae no longer had the same characteristics as the wild strain: some resisted to chlorate or were different as to gas formation. The reduction of nitrate to ammonia by these bacteria is diminished in the presence of chlorate: the reduction of nitrate to nitrite was inhibited or not inhibited according to the type of strain. The bacteria broke down the chlorate partially or completely, according to the strains and the sustrates.