Probably localized either on the surface of the outer spore membrane and/or in the inner spore coat. Expressed in the mother cell compartment from T2 of sporulation. LysM domains are thought to be involved in peptidoglycan binding. According to PubMed:11011148, cells show no effect vegetative growth, spore resistance to heat, chloroform and lysozyme, or spore germination in the presence of L-alanine. According to PubMed:12177332, cells have no detectable alteration in either dormant or germinating spore peptidoglycan, and germinate normally. Transcription of ydhD is dependent on SigE. Cells producing excessive ydhD do not show impaired spore resistance, but their germination properties change: spores show reduced response to L-alanine and some of them germinate even without germinants. Belongs to the glycosyl hydrolase 18 family. Chitinase class II subfamily.