Effects of pesticides on cyanobacterium Plectonema boryanum and cyanophage LPP-1.

Cyanobacterium Plectonema boryanum IU 594 and cyanophage LPP-1 were used as indicator organisms in a bioassay of 16 pesticides. Experiments such as spot tests, disk assays, growth curves, and one-step growth experiments were used to examine the effects of pesticides on the host and virus. Also, experiments were done in which host or virus was incubated in pesticide solutions and then assayed for PFU. P. boryanum was inhibited by four herbicides: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 1,1-dimethyl-3-(alpha, alpha,alpha-trifluoro-m-tolyl)urea ( Fluometeron ), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (Atrazine), 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine ( Ametryn ). One insecticide, 2-methyl-2-(methylthio)-propionaldehyde O-( methylcarbamoyl )oxime (Aldicarb), also inhibited the cyanobacterium. Two insecticides inactivated LPP-1, O,O-dimethyl phosphorodithioate of diethyl mercaptosuccinate (malathion) and Isotox . Isotox is a mixture of three pesticides: S-[2-( ethylsulfinyl )ethyl]O,O-dimethyl phosphorothioate ( Metasystox -R), 1-naphthyl methylcarbamate ( Sevin ) and 4,4'-dichloro-alpha- (trichloromethyl) benzhydrom ( Kelthane ). Two pesticide-resistant strains of P. boryanum were isolated against DCMU and Atrazine. These mutants showed resistance to all four herbicides, which indicates a relationship between these phototoxic chemicals. The results indicate that P. boryanum may be a useful indicator species for phototoxic agents in bioassay procedures.