Global analysis of transcription kinetics during competence development inStreptococcus pneumoniae using high density DNA arrays

The kinetics of global changes in transcription patterns during competence development in Streptococcus pneumoniae was analysed with high-density arra ys. Four thousand three hundred and one clones of a S. pneumoniae library, covering almost the entire genome, were amplified by PCR and gridded at hig h density onto nylon membranes. Competence was induced by the addition of C SP (competence stimulating peptide) to S. pneumoniae cultures grown to the early exponential phase. RNA was extracted from samples at 5 min intervals (for a period of 30 min) after the addition of CSP. Radiolabelled cDNA was generated from isolated total RNA by random priming and the probes were hyb ridized to identical high-density arrays. Genes whose transcription was ind uced or repressed during competence were identified. Most of the genes prev iously known to be competence induced were detected together with several n ovel genes that all displayed the characteristic transient kinetics of comp etence-induced genes. Among the newly identified genes many have suggested functions compatible with roles in genetic transformation. Some of them may represent new members of the early or late competence regulons showing com petence specific consensus sequences in their promoter regions. Northern ex periments and mutational analysis were used to confirm some of the results.