Regulation of AdeABC, AdeFGH, and AdeIJK efflux pumps in A. baumannii. Expression of the AdeABC pump (a) is activated by two two-component systems, AdeRS and BaeRS, low iron conditions, presence of human serum albumin, and presence of ppGpp. AdeFGH (b) expression is repressed by AdeL, a LysR-family protein, encoded upstream of the operon. Human serum albumin and DNA damage are known to increase adeFGH expression. AdeIJK (c) regulation involves the repression by TetR-type regulator AdeN and presence of human serum albumin, and activation by TCS BaeSR and ppGpp. Green solid arrows indicate direct activation of expression. Green dashed arrows indicate an unknown mechanism of activation of expression. Red solid lines indicate direct repression of expression. Red dashed lines indicate an unknown mechanism of inhibition of expression.