Precise amounts of a novel member of a phosphotransferase superfamily are essential for growth and normal morphology in Caulobacter crescentus

Abstract

The Caulobacter crescentus chromosomal clp locus contains the genes encoding the components of ClpXP, a multisubunit protease required for cell cycle progression in this organism. Here, we report the identification and characterization of cicA, a gene located between the clpX and clpP genes on the Caulobacter chromosome. cicA is a novel morphogene in C. crescentus and, like clpX and clpP, is essential for growth. A conditional cicA mutant stopped growth, but retained viability under restrictive conditions. In contrast, an increased concentration of CicA led to an immediate loss of the normal rod shape, an almost 10‐fold increase of the cell's volume and a cell division block. In parallel with this drastic morphological change, cells rapidly lost viability. Primary sequence analysis suggested that the cicA gene encodes a member of a large superfamily of phosphotransferases, that include phosphoserine phosphatases, the ATPase domain of P‐type ATPases and receiver domains of response regulators. Four conserved motifs of this protein family that have been implicated in the catalysis of phosphotransfer reactions were investigated by site‐directed mutagenesis and were found to be critical for in vivo function of CicA. Based on our observations, we postulate that CicA is involved in essential phosphotransferase reactions in Caulobacter and that increased activity of CicA has a deleterious effect on cell wall biosynthesis, morphogenesis and cell division.

Large‐scale identification of essential Salmonella genes by trapping lethal insertions

“…Biased results were obtained for homologous recombination in five non‐essential genes ( sseC , flgH , sipA , purB and spiA ) exhibiting IPC values of essential genes. Because these genes are organized in an operon encoding membrane or secreted proteins, we assume that the plasmid integration lethally disrupted the equilibrated expression of the polycistronic genes (Fuchs et al ., 2001). One intergenic fragment was identified as located at position 19 901 (antisense orientation) of plasmid pSLT, covering the intergenic region between ccdA and a gene encoding a hypothetical protein.…”

Two-Component Signal Transduction Pathways Regulating Growth and Cell Cycle Progression in a Bacterium: A System-Level Analysis

“…Depletion of either gene product led to a severe membrane blebbing phenotype, which, to the best of our knowledge, has not been seen before in C. crescentus . A number of other C. crescentus genes are involved in maintaining cell wall integrity and cell shape, including mreB, rodA, and cicA, but the relationship, if any, of these genes to cenK and cenR is not yet clear [44–46]. …”

Identification of Pseudomonas syringae pv. tomato genes induced during infection of Arabidopsis thaliana

“…The ipx 36 gene encodes a protein with similarity to the muropeptide transporter AmpG, which is involved in the uptake of peptidoglycan turnover products (Holtje, 1998). The ipx 35 fusion defines a cicA-like gene, which has been proposed to be involved in regulating cell wall synthesis and morphology in Caulobacter crescentus (Fuchs et al, 2001). The recent finding that a mutation in the N-acetylmuramyl-L-alanine amidase (ampD) gene of Ralstonia solanacearum results in decreased virulence indicates that functional peptidoglycan recycling is important for the virulence of plant pathogens (Tans-Kersten et al, 2000).…”