Screening and isolation of mutants ofBacillus megateriumB153-2-2 for motility, chemotaxis, antagonism, and sporulation

Abstract Cells of Bacillus megaterium strain B153-2-2 from the exponential growth stage were treated with 0.01 m ethylmethane sulphonate for 1h at 30°C. Mutagenized cells were screened for motility and/or chemotaxis mutation based on swarm morphology. Sixty-eight putative mutants for chemotaxis and/or motility were isolated. The chemotactic phenotype of all mutants was confirmed by capillary assays for their chemotactic response to soybean ( Glycine max ) root exudates. These mutants were tested further for growth rate, sporulation, and antagonism against Rhizoctonia solani . Eight mutants and a previous nitrosoguinadine-induced mutant, M2144, had the same growth rate as original B153-2-2 strain but differed in motility (Mot), chemotaxis (Che), sporulation (Spo), and/or antagonism to R. solani (Ant). By comparison with B153-2-2 (Mot + Che + Ant ++ Spo + ), nine mutants were grouped as follows: SD12 and SD20 (Mot − Che − Ant ++ Spo ++ ), SF8 and SF21 (Mot −/+ Che − Ant ++ Spo ++ ), M2144 (Mot + Che + Ant + Spo + ), R1013 (Mot ++ Che ++ Ant + Spo + ), R518 (Mot ++ Che ++ Ant + Spo − ), and LR1013 and LR518 (Mot +++ Che +++ Ant − Spo − ). Mutant cells with an increase in motility and chemotaxis generally had decreased sporulation and/or in antagonism to R. solani .