Revival of biocide-treated spores of Bacillus subtilis

Spores of Bacillus subtilis NCTC 8236 were treated with biocides and then subjected to various revival procedures. Sodium hydroxide (optimum concentration 25 mmol l-1) revived a small portion of glutaraldehyde-treated spores but not of spores exposed to formaldehyde, polyvinylpyrrolidone-iodine (PVP-I), Lugol's iodine, sodium hypochlorite or sodium dichloroisocyanurate (NaDCC). Post-treatment heat shock (at 70 degrees or 80 degrees C) increased the numbers of colony-forming units (cfu) of formaldehyde-injured spores. Coat-extraction procedures had the greatest effect on iodine-pretreated spores. The uptake of iodine and chlorine was more rapid and occurred to a greater extent with outgrowing, germinating and especially coat-deficient spores than with mature, resting spores.