The Swelling of Bacterial Spores during Germination and Outgrowth

Abstract

The swelling of spores of Bacillus cereus and B. subtilis during germination and outgrowth was followed by measuring changes in packed cell volume (pcv) and by photomicro-graphic measurements of single organisms. Three stages of swelling were recognized: (1) germination swelling involving a rapid increase of about 20% in pcv as the spore germinated; (2) preemergence swelling of up to 100% increase in pcv before emergence from the spore coat; (3) elongation. Germination swelling was due mainly to an increase in the breadth of the spore. It occurred in the absence of oxygen and was not inhibited by nisin, whereas pre-emergence swelling was oxygen-dependent and was inhibited by nisin. Post-emergence swelling occurred during elongation of the new vegetative form. The significance of these findings is discussed.