Role of SpoVA proteins in the release of dipicolinic acid during germination of Bacillus subtilis spores triggered by dodecylamine or lysozyme

Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305 USA

^* To whom correspondence should be addressed. Email: setlow{at}nso2.uchc.edu.

	Abstract

The release of dipicolinic acid (DPA) during germination of Bacillus subtilis spores by the cationic surfactant dodecylamine exhibited a pH optimum of 9 and a temperature optimum of 60°C. DPA release during dodecylamine germination of B. subtilis spores with 4-fold elevated levels of the SpoVA proteins that have been suggested to be involved in release of DPA during nutrient germination was 4-fold faster than DPA release during dodecylamine germination of wild-type spores, and was inhibited by HgCl₂. Spores carrying temperature sensitive mutants in the spoVA operon were also temperature sensitive in DPA release during dodecylamine germination, as well as in lysozyme germination of decoated spores. In addition to DPA, dodecylamine triggered the release of amounts of Ca²⁺ almost equivalent to those of DPA, and at least one other abundant spore small molecule, glutamic acid, was released in parallel with Ca²⁺ and DPA. These data indicate that: 1) dodecylamine triggers spore germination by opening a channel in the inner membrane for Ca²⁺-DPA and other small molecules; 2) this channel is composed at least in part of proteins; and 3) SpoVA proteins are involved in release of Ca²⁺-DPA and other small molecules during spore germination, perhaps by being a part of a channel in the spore's inner membrane.