The sequence of use of amino acids and glucose has been investigated in pure culture studies using Fusobacterium nucleatum. Preferential use of glutamate and lysine before glucose has been documented in both continuous and batch culture for F. nucleatum. A fraction of the glucose was used at all dilution rates in continuous culture while all the glutamate and lysine were used at low dilution rates when the amino acids are limiting. When glucose and glutamate were added to a depleted medium in batch culture, no glucose was used until exhaustion of the glutamate. Incremental additions of glutamate to a batch culture of F. nucleatum, whose medium was depleted of glutamate but not glucose, resulted in growth and glucose use only following addition and use of the glutamate. Glutamate dependent glucose utilization has also been shown with washed suspensions of F. nucleatum. Anaerobiasis was also necessary for glucose transport and of 18 amino acids tested, only glutamic acid, lysine, and histidine supported the transport of glucose. Studies with other hexoses and hexose analogues have shown that only glucose and galactose are transported in this manner. Both glucose and galactose were transported into a stable form in the cells which was not extractable with hot water but which could be extracted with hot alkali and precipitated with ethanol. This product appears to be glycogen when obtained from glucose grown cells. The nature of the polymer resulting from galactose use is unknown and under investigation.
