The Pseudomonas fluorescens Crc affects the length of the transition phase during diauxic growth

Pseudomonads, unlike enteric bacteria, prefer to utilize tricarboxylic acid cycle intermediates over glucose. The crc gene has been implicated to impart repression on glucose and other metabolic enzymes in various Pseudomonas species when grown in a mixture of glucose and various organic acids. The crc gene of P. fluorescens strain MB101 has been identified and a crc deletion derivative was constructed. Unlike a crc mutant of P. aeruginosa described earlier, the P. fluorescens deletion mutant crc did not begin to catabolize glucose until most of the succinate has been utilized in a medium containing both carbon sources. The transition phase during diauxic growth in succinate/glucose media was found to be shorter in a strain lacking crc and considerably longer in a strain overproducing Crc as compared to the wild type. DNA microarray analyses were performed with wild-type and crc mutant strains during the transition phase from succinate to glucose. In the wild-type strain, high expression signals were obtained for genes normally induced in cells that approach or are in stationary phase. By contrast, deletion mutant crc cells showed higher expression signals for genes associated with rapid growth than the wild-type strain. Taken together, this data indicates that Crc influences the length of the lag during the transition phase from succinate to glucose by directly or indirectly affecting the mRNA levels of target genes. Keywords: time course strain comparison These are time course experiments to compare crc mutant strain to the wildtype MB101 strain at 5, 6, 7, 8, and 9 ht time points. Dye swaps were included in each time point comparison. There are 10 pairs in total.