Variations in gene expression with time of phagocytosis. Data from genomic DNA arrays prepared with RNA from bacteria at the conclusion of the preopsonization step (t = 0, n = 4) and 7 minutes (n = 5), 15 minutes (n = 4), and 30 minutes (n = 4) after the addition of neutrophils. (a) Expression ratios for prominent genes of the oxyR regulon: ahpC (filled diamonds), ahpF (filled squares), dps (filled triangles), hemH (open triangles), katG (open squares), trxC (open diamonds), and oxyR (filled circles with error bars reflecting SEM). (b) Expression ratios for genes of the ast operon (32) regulated by the NtrC transcription factor (26), astEBDAC: astE (diamonds), astB (squares), astD (triangles), astA (X’s), and astC (asterisks). (c) A newly described NtrC-regulated operon of unknown function b1012 → b1008, possibly pyrimidine metabolism (26, 33): b1012 (filled diamonds), b1011 (filled squares), b1010 (filled triangles), b1009 (open triangles), b1008 (squares).