1.A.134.  The Nutrient-sensing Ion-conducting Pore-forming GerAA (NIP-GerAA) Family

Bacterial spores resist antibiotics and sterilization and can remain metabolically inactive for decades, but they can rapidly germinate and resume growth in response to nutrients (amino acids, sugars and nucelosides/tides). Broadly conserved receptors embedded in the spore membrane detect nutrients. Gao et al. 2023 found that these receptors form oligomeric membrane channels. Mutations predicted to widen the channel initiated germination in the absence of nutrients, whereas those that narrow it prevented ion release and germination in response to nutrients. Expressing receptors with widened channels during vegetative growth caused loss of membrane potential and cell death, whereas the addition of germinants to cells expressing wild-type receptors triggered membrane depolarization. Therefore, germinant receptors act as nutrient-gated ion channels such that ion release initiates exit from dormancy. GerAA is believed to be the ion channel component; GerAB is the nutrient sensor, and GerAC is a membrane surface lipoprotein (Gao et al. 2023). The NIP-GerAA family includes only the ion channel subunit.