The influence of intracellular polyglucose and prior growth rate on the survival of Fusobacterium nucleatum under starvation conditions

Abstract

Grown in a chemically defined medium containing glucose at a dilution rate of D = 0.065 h-1, Fusobacterium nucleatum D212B-2 produced large amounts of intracellular polyglucose. Aliquots of this culture were starved by anaerobic incubation at 37 degrees C and at various times, assayed for intracellular polyglucose content and viability. This protocol was repeated using cells grown under the same conditions in a chemically defined medium, a medium lacking carbohydrate and in which the organism produced no intracellular polyglucose. Both cultures had 50% survival time values of about 1.5 h and were not eliminated even after 32 h of starvation. It was, therefore concluded that starvation-survival is not influenced by intracellular polyglucose. Starvation-survival was also determined for cells grown in a chemically defined medium at D = 0.048 h-1 and D = 0.12 h-1. The faster-grown cells had a 50% survival time of 3.8 h but were completely eliminated after 8-16 h of starvation. In contrast, slower-grown cells had a 50% survival time of 1.5 h but were not completely eliminated after 32 h of starvation. This illustrates the importance of cell history and technique standardization in comparing the starvation-survival of different organisms.