Expression Profiling of Translation-associated Genes in SporulatingBacillus subtilisand Consequence of Sporulation by Gene Inactivation

A DNA microarray technique was used to demonstrate global changes in the transcription pattern of translation-associated genes that encode fifty-four ribosomal proteins including a putative ribosomal gene, and eleven translation factors in sporulating B. subtilis. We found that the mRNA levels of nine genes involved in the translation system, which include the genes for three ribosomal proteins (rpmA, rpmGB, and ctc) and two translation factors (efp, and frr), were maintained at a high level at the onset of sporulation. The ypfD gene, which encodes the ribosomal protein S1 homologue, was also found to be expressed significantly during the early sporulation stage. In order to demonstrate the significance of these genes for sporulation, mutants were constructed using the pMutinT3 disruption vector. We detected an impaired sporulation in the mutants of rpmA (gene for the ribosomal protein L27), efp (elongation factor P), frr (ribosome recycling factor), and ypfD. The effect was especially pronounced in the efp mutant, sporulation of which was entirely abolished without affecting growth. The reduced expression of rpmGB (ribosomal protein L33) resulted in an impaired sporulation only at a high temperature (47 degrees C). Only the rplI mutant, which encodes the ribosomal protein L9, could not be obtained, implying that its function is essential for viability. Thus, we successfully demonstrated the significance of several translation-associated genes in sporulation by using the results of the gene expression profiling.