RNA Extraction，Dot Blots，and Northern Hybridization
Total cellular RNA was extracted as previously described［40］，except that a minipreparation was developed by reducing the cell volume to 10 ml to handle large numbers of samples more easily.The yields of total RNA per 10 ml of cells was about 300 μg，enough for dot blots and Northern hybridization analysis.The labeling of plasmid DNA，phage DNA，oligonucleotides，and all dot blot and Northern hybridizations were as previously described［39，42］.(https://www.daowen.com)
