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Developmental switch within the bacterial cell cycle regulator CtrA

ABSTRACT: Many bacteria acquire dissemination and virulence traits in G1-phase. CtrA, an essential and conserved cell cycle transcriptional regulator identified in the dimorphic alpha-proteobacterium Caulobacter crescentus, mysteriously switches from activating promoters in late S-phase to a different set in G1-phase. We found that a core and highly conserved determinant in the DNA-binding domain (DBD) of CtrA governs this promoter switch and that it is also required for promoter reprogramming in stationary phase in response to a (p)ppGpp alarmone signal perceived by the RNA polymerase beta subunit. A simple side chain modification in one critical residue of this DBD confers opposing developmental phenotypes and transcriptional activities. This region is also central to understanding the developmental reprogramming in the obligate intracellular Rickettsiae where replicative cells develop into dispersal cells and a naturally occurring polymorphism in the rickettsial DBD resembles a mutation that drives CtrA towards activation of the dispersal (G1-phase) program in Caulobacter.

ORGANISM(S): Caulobacter vibrioides NA1000

PROVIDER: GSE134017 | GEO | 2019/11/25

REPOSITORIES: GEO

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Project description:Investigation of whole genome expression changes in Magnetospririllum magneticum mutants, probing the role of the CtrA regulatory pathway. The mutants are further described in a manuscript submitted for publication at J. Bacteriology. Developmental events across the prokaryotic life cycle are highly regulated at the transcriptional and post-translational levels. Key elements of a few regulatory networks are conserved among phylogenetic groups of bacteria, although the features controlled by these conserved systems are as diverse as the organisms encoding them. In this work, we probe the role of the CtrA regulatory network, conserved throughout the Alphaproteobacteria, in the magnetotactic bacterium, Magnetospirillum magneticum strain AMB-1, which possesses unique intracellular organization and compartmentalization. While we show that CtrA in AMB-1 is not essential for viability, it is required for motility, and its putative phosphorylation state dictates the ability of CtrA to activate the flagella biosynthesis gene cascade. Gene expression analysis of strains expressing active and inactive CtrA alleles point to the composition of the extended CtrA regulon, including both direct and indirect targets. These results, combined with a bioinformatic study of the AMB-1 genome, enabled the prediction of an AMB-1 specific CtrA binding site. Further, phylogenetic studies comparing CtrA sequences from Alphaproteobacteria in which the role of CtrA has been experimentally examined reveals an ancestral role of CtrA in the regulation of motility and suggests that its essential functions in other Alphaproteobacteria were acquired subsequently. Total RNA was recovered from each of the wild-type and mutant strains, reverse transcribed to cDNA, fluorescently labeled, and hybridized to whole genome microarrays. The arrays contain 7 probes/gene, with the entire genome duplicated twice. In addition, the arrays contain 7 probes for 22 unannotated ORFs and tiling of a genomic region from coordinates 977403-1097027.

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Developmental switch within the bacterial cell cycle regulator CtrA

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