DETERMINATION OF THE WATER NECESSARY FOR SURVIVAL OF BACILLUS-SUBTILIS VEGETATIVE CELLS AND SPORES

To determine the minimal amount of water necessary for survival in Bac illus subtilis, bound and free water were measured by time domain refl ectometry (TDR) and the gel-sol phase transition of bound water was me asured by differential thermal analysis-thermogravimetry (DTA-TG). Bot h the vegetative and the spore form of Bacillus subtilis were dried at different temperatures. From the measurements, the relationship betwe en survival of the bacteria and water can be summarized as follows. (1 ) The vegetative form of bacteria was still 100% viable even when 80% of bound water was removed. (2) The spore form contained only 20% of b ound water, which was easily and quickly removed by drying, and result ed in loss of viability. (3) Phase transition between gel and sol phas es of bound water occurred repeatedly in the dried vegetative 100%-via ble bacteria, which still had 20% bound water. The bacteria were still viable after such measurements. (4) In the spore form, phase transiti on was not detected.