Expression data from E. coli cells overexpressing either GreA or GreB in ppGpp0 cells in the dksA+ or dksA- background

Strains devoid of ppGpp (relA spoT; called ppGpp0), and ppGpp0 dksA- exhibit several amino acid requirements for growth on minimal media. We found that overexpression of DksA can complement some of those requirements. Since DksA is a factor that binds to the RNA polymerase secondary channel, we wondered if other secondary channel proteins might also exert a similar role with respect to growth on minimal media. In our study we found that GreA and partially GreB can in fact complement these requirements under certain conditions. Here, we wished to investigate a broader effect of GreA and GreB on ppGpp0 and ppGpp0 dksA- strains. Since the parent strains are unable to grow in minimal media, we had to supplement the M9 glucose medium with a set of amino acids (DFHILQSTV). We found that both, GreA and GreB can affect a much larger set of genes in the absence of dksA, than in its presence. Also, GreA seems to affect more genes than GreB, under both conditions.

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Vinella D, Potrykus K, Murphy H, Cashel M