ABSTRACT
Introduction .......................................................................................................... 24 Global Regulators of Antibiotic Resistance in Escherichia coli ......................... 25
The mar Regulatory Locus ....................................................................... 25 The soxRS System ..................................................................................... 27 Rob-A Third Regulator? ........................................................................ 28 A Single Regulon with Two Activators .................................................... 28 Regulon Targets and Antibiotic Resistance .............................................. 28
micF ............................................................................................... 29 acrAB and tolC .............................................................................. 29 marRAB ......................................................................................... 30
Mechanisms of Regulon Induction and Physiological Roles .................... 30 Additional Mar-Like Systems Involving Small AraC/XylS-Like
Activators ....................................................................................... 32 Intrinsic Acetyltransferases in Bacteria .................................................... 32
AAC(2′)-Ia in Providencia stuartii ..................................................................... 33 Physiological Functions ............................................................................ 33 Genetic Regulation ................................................................................... 33 Negative Regulators .................................................................................. 34
aarA ................................................................................................ 34 aarB ................................................................................................ 34 aarC ............................................................................................... 34 aarD ............................................................................................... 35 aarG ............................................................................................... 35
Positive Regulators of aac(2′)-Ia .............................................................. 36 aarE ................................................................................................ 36 aarF ................................................................................................ 36 aarP ................................................................................................ 36
Role of Quorum Sensing in aac(2′)-Ia Regulation .................................. 37 Concluding Remarks ............................................................................................ 38 References ............................................................................................................ 38
The majority of attention on antibiotic resistance mechanisms has been justifi ably focused on those factors that are highly transmissible among species and that lead to high levels of resistance to a specifi c class of antibiotics. Less is known about the ability of bacteria to alter their susceptibility to noxious agents by modulating their own intrinsic physiological systems. In this chapter, we describe two of the better-studied examples of this latter situation, both of which occur in Gramnegative species.
