Positive values show phenotypes

Positive values show phenotypes FK228 manufacturer gained in rpoS mutants while negative values show phenotypes lost because of rpoS mutations. In total, rpoS mutants grew better on 92 nitrogen sources tested, and the top 10 are listed. Enhanced growth of Suc++ (rpoS + and rpoS -) mutants is not limited to the TCA cycle intermediates To extend the phenotype screening results to pathogenic E. coli, we tested the growth of EDL933 and derivative rpoS and Suc++ (rpoS + and rpoS -) mutants on selected carbon sources (20 mM each) that best supported differential respiration of rpoS mutants relative to wild type (Figure 4). Glucose and succinate were also tested as controls for comparison.

As expected, compared with wild type, the rpoS and Suc++ mutants grew similarly on glucose but much better on succinate. Among the Biolog compounds tested, I-BET151 solubility dmso the rpoS and Suc++ mutants, including the Suc++(rpoS +) mutants, grew better than wild type on D-glucuronic acid or glutamine as the sole carbon source. However, none of these strains could grow on threonine or proline as the sole carbon source, which is likely due to differences in strain background and experimental conditions. The enhanced growth of mutants on D-glucuronic acid and glutamine confirmed that mutations selected on succinate have pleiotropic effects on utilization of other nutrient sources.

Figure 4 Growth of EDL933 and derivative mutants on different carbon sources. “”ND”": not detected. Cells were grown in LB media to OD600 0.6, washed and inoculated to fresh media to a starting OD600of 0.05. Cultures were then grown at 37°C with vigorous shaking (200 rpm) and sampled every hour for 10 hours to monitor growth. D-glucuronic acid, threonine, glutamine or proline were added to M9 minimal media as the sole carbon SB202190 molecular weight source to a final concentration of 20 mM.

Discussion Understanding how pathogens adapt and mutate in response to growth environments is critical in deciphering many of the unknowns regarding pathogenesis, such as the emergence of new pathogens, the increased resistance to antibiotics, and the long-term persistence in host environment. In this study, we report that a metabolic selection mechanism for loss of RpoS, a central stress buy Abiraterone and adaptation regulator, in representative verocytotoxin-producing E. coli strains, may be responsible for the occurrence of rpoS mutations among pathogenic E. coli isolates. In surveying the rpoS gene among E. coli isolates, we found many mutations in rpoS, some of which result in loss of RpoS function. Among the VTEC strains tested, most grow poorly on succinate (like laboratory K12 strains) but some strains grow well. Those that grow poorly all have intact rpoS. In contrast, strains that grow well on succinate can be distinguished into two groups, one with intact rpoS and the other with truncated rpoS.

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