Detection of mRNA for P21 and P16. Total RNA sample was prepared from G. thermoleovorans B23 cultures before (indicated as 0 day in the figure) or after (4 and 10 days) induction by alkanes. Positive signals were indicated by arrowheads. a, Northern blot analysis of mRNA for P21. AlkPhos-labeled DNA probe gives signal at ca. 700 bases, where it hybridizes to mRNA for P21 on the membrane. b, Detection of mRNA for P16 by RT-PCR analysis.