BIOCHEMICAL-CHANGES ACCOMPANYING THE LONG-TERM STARVATION OF MICROCOCCUS-LUTEUS CELLS IN SPENT GROWTH-MEDIUM

Changes in the biochemical properties of Micrococcus luteus cells were studied during the transition to a dormant state after incubation in an extended stationary phase. The overall DNA content after 150 days o f starvation was similar to its initial level, while the RNA content d ecreased by 50%. Total lipids and protein, phospholipids and membrane proteins declined rapidly within the first 1-10 days of starvation. Af ter 180 days of starvation, cells contained 43% of the protein and 35% of the lipid initially present. Starvation for 120 days resulted in t he loss of phosphatidylglycerol and, to some extent, of phosphatidylin ositol, giving a membrane whose phospholipids consisted mainly of card iolipin. The membrane fluidity declined during starvation, as judged b y diphenyl hexatriene fluorescence anisotropy measurements. Oxidase ac tivities declined to zero within the first 20-30 days of starvation, w hile the dehydrogenases and cytochromes were more stable. The activiti es of some cytoplasmic enzymes were lost very rapidly, while NADPH-lin ked isocitrate dehydrogenase had 30% of its initial activity after 120 days of starvation. For all parameters tested there were significant fluctuations during the first 10-20 days of starvation, which may refl ect cryptic growth in the culture.