The effects of heat activation on bacillus spore germination, with nutrients or under high pressure, with or without various germination proteins

Abstract

Nutrient germination of spores of Bacillus species occurs through germinant receptors (GRs) in spores'inner membrane (IM) in a process stimulated by sublethal heat activation. Bacillus subtilis spores maximum germination rates via different GRs required different 75C heat activation times: 15 min for L-valine germination via the GerA GR and 4 h for germination with the L-asparagine glucose fructose K mixture via the GerB and GerK GRs, with GerK requiring the most heat activation. In some cases, optimal heat activation decreased nutrient concentrations for half-maximal germination rates. Germination of spores via various GRs by high pressure (HP) of 150 MPa exhibited heat activation requirements similar to those of nutrient germination, and the loss of the GerD protein, required for optimal GR function, did not eliminate heat activation requirements for maximal germination rates.