Bacillus sphaericus was transformed by electroporation as described by Li et al. (2000) and cells were grown in Luria–Bertani (LB) broth or MBS broth (Kalfon et al., 1984), which RG7204 datasheet contains (g L−1): MgSO4·7H2O, 0.3; MnSO4, 0.02; Fe2(SO4)3, 0.02; ZnSO4·7H2O, 0.2; CaCl2, 0.2; tryptose, 10; yeast extract, 2; the pH was adjusted to 7.4 and incubation was usually carried out at 30 °C; E. coli strains were grown in LB medium at 37 °C. Antibiotics used for bacterial selection included (μg mL−1): 100 ampicillin (Amp) or 100 spectinomycin

(Spc) for E. coli and 200 spectinomycin, or 25 erythromycin (Erm) or 50 kanamycin (Kan) for B. sphaericus. For solid medium, agar was added to a final concentration of 1.5% (w/v). The mariner-based transposon pMarB333 (Li et al., 2009) was transformed into B. sphaericus strain 2297 and the transformants were selected on LB broth agar containing 200 μg mL−1 Spc and 25 μg mL−1 Erm at 30 °C. After verifying the transformants by PCR, isolated transformants containing pMarB333 were cultured in LB for 6–8 h at 30 °C, and then appropriately diluted cultures were spread on LB agar containing 200 μg mL−1 Spc at 42 °C (a nonpermissive temperature for the plasmid replication) for 24 h. Clones displaying SpcR ErmS were selected as mutants. The chromosomal DNA of the mutants was digested with HindIII (the restriction site that is absent in mariner transposon) Adriamycin order and the digested genomic DNA was re-ligated. As the mariner

transposon has an E. coli origin of replication, the ligation mixture was used to transform E. coli DH5α, and spectinomycin-resistant transformants were selected. Plasmid DNA was prepared from the transformants and the restriction map of the plasmid was determined to verify the presence of mariner transposon (a 2.2-kb BamHI fragment is characteristic of mariner transposon). DNA flanking the mariner transposon element was sequenced

from plasmid DNA with primer MarB333 (5′AAAGCGTCCTCTTGTGAAAT3′). The flanking DNA sequences of mariner transposon insertion were compared with the GenBank database using the blastx, blastp or psi-blast tools available online at the National Center for Biotechnology Information (NCBI; Ye et al., 2006). Southern blot analysis was performed Sclareol using a DIG High Prime DNA labeling and detection starter kit (Roche, Indianapolis, IN). About 1200 colonies of mutants were toothpicked on MBS plates and incubated at 30 °C for 72 h. The mutant manifested as pale translucent colonies and were selected (Isezaki et al., 2001) and further examined by observation with a phase-contract microscope. The strains that did not exhibit the bright mature spores were defined as sporulation-defective mutants (Holt et al., 1975). Sporulation was induced by nutrient exhaustion in MBS broth at 30 °C for 72 h, and cells were fixed and embedded in Epon812 resin and subjected to ultrathin sectioning. Thin-section electron microscopy was performed as described previously (Yousten & Davidson, 1982).