Effect of hypergravitational stress on microbial cell viability

Cell of Escherichia coil B, Thiobacillus intermedius 13-1, Bacillus amyloli quefaciens IFO14141, Staphylococcus aureus IID975, and Saccharomyces cerevi siae Kyokai no. 7 cultivated in nutrient media were subjected to hypergravi tational stress for a period of between 1 and 24h at 450,000x g. The E. coi l, B. amyloliquefaciens and S. cerevisiae cells showed survival rates of 38 .5%, 0.005%, and 14.7%, respectively, after gravity treatment for 24 h as d etermined by their ability for colony formation, whereas a survival rate of S. cerevisiae cells of almost 100% was observed as determined using the me thylene blue reduction test. E. coil cells, either in the logarithmic growt h phase or cultivated in minimum media, were more sensitive to gravitationa l stress than those either in the stationary phase or cultivated in nutrien t media.