Studies on the Sensitivity of Several Strains in Genus Spirillum to Some Chemicals : (Part 2) Sensitivity of Spirilla and Other Bacteria to Some Herbicides

Sensitivity of Spirilla and other bacteria to four herbicides was examined by MIC and MBC methods. Bacterial strains used were three strains of Aquaspirilla and two of Oceanospirilla. As the controls, one each of Bacillus subtilis, Clostridium sporogenes, Staphylococcus aureus and Escherichia coli was used. The herbicides used were Roundup (Isopropylamino-N-(phosphonomethyl)glycine), Gramokison(1, 1'-dimethyl-4,4'-bipyridylium dichloride), 2,4-D (Dimethylamino-2,4-dichlorophenoxyacetate) and CIPC (Isopropyl-N- (3-chlorophenyl)carbamate). The experimental results obtained are as follows: 1) No strain of spirilla and the controls was affected to the herbicides tested at the concentration of practical use (5 × 10-^4%) in the field. However, the Spirilla and the controls showed more than ten times higher sensitivity to the herbicides than to phenol. 2) The Spirilla strains were more sensitive to all herbicides than the controls. Sensitivity of spore-forming bacteria, B. subtilis, C. sporogenes and the other controls to the herbicides made little difference. 3) The MBC values were higher than the MIC values in all strains tested. 3) Both values of MIC and MBC for 2,4-D in all strains were the highest among the herbicides tested. Other three herbicides showed nearly the same values. Thus the basic data on sensitivity of Spirilla to some herbicides showed that these strains might be valid as the markers in the detection of chemical pollution, because of their higher sensitivity than the controls.