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 clhAB(2) operon is required for this chain lengthening phenotype. The clhAB(2) 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 (ΔclhAB(2)) was constructed and our quantitative image analyses show that ΔclhAB(2) cells formed abnormal short chains regardless of the presence of glucose. We also found that glucose-grown cells of ΔclhAB(2) 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, ΔclhAB(2) cells showed accelerated autolysis under autolysis- inducing conditions, compared to wild-type cells. Overall, our data suggest that the B. cereus clhAB(2) 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 clhAB(2) using a lacZ transcriptional reporter in wildtype, ccpA and codY deletion-mutant strains. We found that the global transcriptional regulatory protein CodY is required for the basal level of clhAB(2) 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 clhAB(2) in glucose-grown cells.