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Keywords:

  • Bacillus ;
  • bacterial spores;
  • Ca-DPA;
  • dodecylamine;
  • spore germination;
  • spores;
  • superdormant

Abstract

Aims

To isolate and characterize spores superdormant (SD) for germination with either Ca2+-dipicolinic acid (CaDPA) or dodecylamine.

Methods and Results

Bacillus subtilis spores were germinated three times with either CaDPA or dodecylamine and germinated spores removed after each germination treatment, yielding 0·9% (CaDPA-SD spores) or 0·4% (dodecylamine-SD spores) of initial dormant spores. Compared to dormant spores, CaDPA-SD spores germinated poorly with CaDPA and better with dodecylamine and nutrient germinants, although release of DPA from individual CaDPA-SD spores was slow during nutrient germination, and this germination was strongly inhibited by TbCl3. The CaDPA-SD spores were sensitive to hypochlorite and had elevated levels of nutrient germinant receptors (GRs) relative to levels in dormant spores. Dodecylamine-SD spores' germination with dodecylamine and nutrients was similar to that of dormant spores, their germination with Ca-DPA was slower than that of dormant spores, and these SD spores' GR levels were lower than in dormant spores. However, dodecylamine-SD spores were not sensitive to hypochlorite, and the nutrient germination of these SD spores was only partially inhibited by TbCl3.

Conclusions

CaDPA-SD spores appear to have a coat defect and accompanying low levels of the cortex-lytic enzyme CwlJ. The defect in dodecylamine-SD spores, however, is not clear.

Significance and Impact of the Study

The results suggest that triggering germination by non-GR-dependent germinants is a potential strategy for efficient spore inactivation.