A glutamate‐alanine‐leucine (EAL) domain protein of Salmonella controls bacterial survival in mice, antioxidant defence and killing of macrophages: role of cyclic diGMP

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Abstract
Summary: Signature‐tagged transposon mutagenesis of Salmonella with differential recovery from wild‐type and immunodeficient mice revealed that the gene here named cdgR[for c‐diguanylate (c‐diGMP) regulator] is required for the bacterium to resist host phagocyte oxidase in vivo. CdgR consists solely of a glutamate‐alanine‐leucine (EAL) domain, a predicted cyclic diGMP (c‐diGMP) phosphodiesterase. Disruption of cdgR decreased bacterial resistance to hydrogen peroxide and accelerated bacterial killing of macrophages. An ultrasensitive assay revealed c‐diGMP in wild‐type Salmonella with increased levels in the CdgR‐deficient mutant. Thus, besides its known role in regulating cellulose synthesis and biofilm formation, bacterial c‐diGMP also regulates host–pathogen interactions involving antioxidant defence and cytotoxicity.