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

Abstract

Cells of Bacillus megateriumstrain B153-2-2 from the exponential growth stage were treated with 0.01 methylmethane 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.