The CodY-dependent clhAB2 operon is involved in cell shape, chaining and autolysis in Bacillus cereus ATCC 14579

Abstract

The Gram-positive pathogen Bacillus cereus is able to grow in chains of rod-shaped cells, but the regulation of chaining remains largely unknown. Here, we observe that glucose-grown cells of B. cereus ATCC 14579 form longer chains than those grown in the absence of glucose during the late exponential and transition growth phases, and identify that the clhAB2 operon is required for this chain lengthening phenotype. The clhAB2 operon is specific to the B. cereus group (i.e., B. thuringiensis, B. anthracis and B. cereus) and encodes two membrane proteins of unknown function, which are homologous to the Staphylococcus aureus CidA and CidB proteins involved in cell death control within glucose-grown cells. A deletion mutant (ΔclhAB2) was constructed and our quantitative image analyses show that ΔclhAB2 cells formed abnormal short chains regardless of the presence of glucose. We also found that glucose-grown cells of ΔclhAB2 were significantly wider than wild-type cells (1.47 μm ±CI95% 0.04 vs 1.19 μm ±CI95% 0.03, respectively), suggesting an alteration of the bacterial cell wall. Remarkably, ΔclhAB2 cells showed accelerated autolysis under autolysis-inducing conditions, compared to wild-type cells. Overall, our data suggest that the B. cereus clhAB2 operon modulates peptidoglycan hydrolase activity, which is required for proper cell shape and chain length during cell growth, and down-regulates autolysin activity. Lastly, we studied the transcription of clhAB2 using a lacZ transcriptional reporter in wild-type, ccpA and codY deletion-mutant strains. We found that the global transcriptional regulatory protein CodY is required for the basal level of clhAB2 expression under all conditions tested, including the transition growth phase while CcpA, the major global carbon regulator, is needed for the high-level expression of clhAB2 in glucose-grown cells.

Chemical Biology Reveals Involvement of N-acetylglucosaminidase LytG In Cell Elongation and Division.

“…38 In addition to activating branched chain amino acid synthesis 38 CodY modulates clhAB2 operon which is involved in cell shape and regulating autolytic acitivity in B. cereus. 39 Inhibition of LytG by Mas, initiates a cellular response of disregulated cell elongation and division and an increased level of PG cross-linking that results in elevated stiffness in the cell wall. This increased stiffness is likely the inducer of the cell wall stress response which in turn influences operons and genes involved in cell shape and elongation.…”

Chemical Biology Reveals Involvement of N-acetylglucosaminidase LytG In Cell Elongation and Division.

“…38 In addition to activating branched chain amino acid synthesis 38 CodY modulates clhAB2 operon which is involved in cell shape and regulating autolytic acitivity in B. cereus. 39 Inhibition of LytG by Mas, initiates a cellular response of disregulated cell elongation and division and an increased level of PG cross-linking that results in elevated stiffness in the cell wall. This increased stiffness is likely the inducer of the cell wall stress response which in turn influences operons and genes involved in cell shape and elongation.…”

Cell death dependent on holins LrgAB repressed by a novel ArsR family regulator CdsR

“…Within the B. cereus group, there are three additional homologs of lrgA, namely cidA, clhA1, and clhA2 [5,45]. While disrupting of B. anthracis clhAB2 had a minor impact on murein hydrolase activity, it was found to be crucial for sporulation [5].…”