Identification of Germinants and Expression of Germination Genes in Strains Isolated from Diarrheic Animals.

In this study, we investigated the spore germination phenotype of strains isolated from diarrheic animals (animal strains). The transcripts of germination-specific genes and their protein products were also measured. Our study found the following results: (i) animal strains spores germinated at a slower rate with AK (mixture of L-asparagine and KCl), L-cysteine, or L-lysine, but the extent of germination varied based on strains and germinants used; (ii) none of the amino acids (excluding L-cysteine and L-lysine) were identified as a universal germinant for spores of animal strains; (iii) animal strain spores germinated better at a pH range of 6.0-7.0; (iv) all tested germination-specific genes were expressed in animal strains; the levels of expression of major germinant receptor gene () were higher and the cortex hydrolysis machinery genes ( and ) were lower in animal strains, compared to the food poisoning strain SM101; and (v) the levels of CspB and SleC were significantly lower in spores of animal strains compared to strain SM101, suggesting that these animal strains lack an efficient spore cortex hydrolysis machinery. In summary, our findings suggest that the poor or slow spore germination in animal strains might be due to incomplete spore cortex hydrolysis.