Transcription of DNA repair genes is not induced significantly by UV irradiation. Known DNA repair genes are grouped by function, with time points for 30 minutes (white), 60 minutes (light grey), 90 minutes (dark grey) and 120 minutes (black) after irradiation shown. Ratios of gene expression for the UV-treated and control cultures are expressed in a log base 2 format, so that a value of 1 represents a two-fold increase in transcription and a value of -1 represents a two-fold decrease (indicated by horizontal grey lines). Few data points show an induction greater than two-fold. By contrast, lanes 22-24 show the highly induced genes cdc6-2, dpoII and tfb3, respectively. Repair genes are all from S. solfataricus (Table 1): 1, xpf; 2, xpb2; 3, fen1; 4, xpd; 5, radA; 6, hjc; 7, hje; 8, rad50; 9, mre11; 10, nurA; 11, herA; 12, ssb; 13, endoIII; 14, endoIV; 15, endoV; 16, mutT; 17, ogg1; 18, ogt; 19, udgaseIVa; 20, udgaseIVb; 21, udgaseVI. Data for S. acidocaldarius repair genes are qualitatively similar (Table 1).