Abstract
Germinant receptors (GRs) initiate spore germination in response to nutrient signals. While their roles are well studied in Bacillus spp., less is known in strict thermophiles such as (Para)Geobacillus spp. This study evaluated the roles of the GR operons identified in Parageobacillus thermoglucosidasius NCIMB 11955 (gerK1, gerK2, and gerX1) in germination and outgrowth. The GerK1 ortholog was essential for germination in TSB supplemented with yeast extract (TSBYE), D-fructose, and D-mannose; it cooperated with GerX1 for germination in maltose, sucrose, and raffinose; with GerK2 or GerX1 for germination in D-arabinose, D-glucose, and D-xylose; and with both for germination in lactose. GerK1 also dominated colony formation on TSA supplemented with yeast extract (TSAYE), but maximal recovery required GerX1 and GerK2, suggesting their involvement in spore outgrowth.