High pressure germination of Bacillus subtilis spores with alterations in levels and types of germination proteins.

AIMS: Examine effects of different levels and types of nutrient germinant receptors (GRs) and other germination proteins on Bacillus subtilis spore germination by a moderate high pressure (mHP) (150 megaPascals (MPa)) that triggers germination through GRs, and a very high pressure (vHP) (550 MPa) that triggers spore germination independent of GRs. METHODS AND RESULTS: The Moderate HP (mHP) and vHP germination kinetics of B. subtilis spores with large variations in levels of GRs and other germination proteins, including the GerD protein and the SpoVA proteins that comprise a spore membrane channel that is likely opened by vHP were measured. CONCLUSIONS: GR levels were the major factor determining mHP germination rates. However, other factors modulated mHP germination rates including (i) relative levels of individual GRs (GerA, GerB, GerK), as mHP affected different GRs differently; (ii) levels of a recently identified small protein that may be a GR subunit; and (iii) a dominant negative mutation in gerD that eliminates GR-dependent nutrient germination. In contrast, the alterations in germination proteins had no major effect on vHP germination, except for reduction of SpoVA protein levels. SIGNIFICANCE AND IMPACT OF THE STUDY: With the increasing use of HP for food processing, this study provides new information on factors that modulate HP germination of spores for potential application of HP technology to achieve food sterility.

Effects of Mn levels on resistance of Bacillus megaterium spores to heat, radiation and hydrogen peroxide.

AIMS: To determine the effects of Mn levels in Bacillus megaterium sporulation and spores on spore resistance. METHODS AND RESULTS: Bacillus megaterium was sporulated with no added MnCl(2) and up to 1 mmol l(-1) MnCl(2). The resultant spores were purified and loosely bound Mn removed, and spore Mn levels were found to vary c. 100-fold. The Mn level had no effect on spore γ-radiation resistance, but B. megaterium spores with elevated Mn levels had higher resistance to UVC radiation (as did Bacillus subtilis spores), wet and dry heat and H(2)O(2). However, levels of dipicolinic acid and the DNA-protective α/ß-type small, acid-soluble spore proteins were the same in spores with high and low Mn levels. CONCLUSIONS: Mn levels either in sporulation or in spores are important factors in determining levels of B. megaterium spore resistance to many agents, with the exception of γ-radiation. SIGNIFICANCE AND IMPACT OF THE STUDY: The Mn level in sporulation is an important factor to consider when resistance properties of B. megaterium spores are examined, and will influence the UV resistance of B. subtilis spores, some of which are used as biological dosimeters.