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Summary The diversity of cell shapes across the bacterial kingdom reflects evolutionary pressures that have produced physiologically important morphologies. While efforts have been made to understand the regulation of some prototypical cell morphologies such as that of rod‐shapedEscherichia coli, little is known about most cell shapes. ForCaulobacter crescentus, polar stalk synthesis is tied to its dimorphic life cycle, and stalk elongation is regulated by phosphate availability. Based on the previous observation thatC. crescentusstalks are lysozyme‐resistant, we compared the composition of the peptidoglycan cell wall of stalks and cell bodies and identified key differences in peptidoglycan crosslinking. Cell body peptidoglycan contained primarily DD‐crosslinks betweenmeso‐diaminopimelic acid and D‐alanine residues, whereas stalk peptidoglycan had more LD‐transpeptidation (meso‐diaminopimelic acid‐meso‐diaminopimelic acid), mediated by LdtD. We determined thatldtDis dispensable for stalk elongation; rather, stalk LD‐transpeptidation reflects an aging process associated with low peptidoglycan turnover in the stalk. We also found that lysozyme resistance is a structural consequence of LD‐crosslinking. Despite no obvious selection pressure for LD‐crosslinking or lysozyme resistance inC. crescentus, the correlation between these two properties was maintained in other organisms, suggesting that DAP‐DAP crosslinking may be a general mechanism for regulating bacterial sensitivity to lysozyme.