FIG. 3.

Expression analysis of asnB, asnH, and asnO in B. subtilis cells grown in a rich sporulation medium. (A) Expression of lacZ reporters fused with each of the asparagine synthetase homolog genes. Cells of B. subtilis 168 (wild type), BFS55 (asnH::pMUTIN2mcs), BFS56 (asnB::pMUTIN2mcs), and FU339 (asnO::pMUTIN2mcs) were cultured in DSM. At various intervals, cells in 1 ml of the cultures were harvested, and β-galactosidase activity (nanomoles of 2-nitrophenyl-β-d-galactopyranoside hydrolyzed per minute per OD₆₀₀ unit) in cell extracts was determined as described previously (22). Activities of the asnB-lacZ fusion in cells of strain BFS56 (left), asnH-lacZ in cells of strain BFS55 (middle), and asnO-lacZ in cells of FU339 (right) are shown as solid squares, and that of endogenous lacZ in cells of strain 168 are shown as open squares. The OD₆₀₀ for cells is shown as solid and open circles for each of the mutants and the wild type, respectively. (B) Northern analysis. Results of Northern analyses for the asnB (left), asnH (middle), and asnO (right) transcriptions are shown. RNAs were prepared from cells of strain 168 grown in DSM. The RNA samples were taken during exponential growth (lane 1), at the time of transition between exponential growth and stationary phase (lane 2), and at 1 h (lane 3) and 5 h (lane 4) after the beginning of sporulation. Positions of size marker RNAs (Millennium markers; Ambion) are given on the left of each panel. Positions of major transcripts are indicated with arrows.