Growth of Aerobacter aerogenes on D-arabinose and L-xylose.

Aerobacter aerogenes is noted for its versatility in being capable of growth by utilizing many of the rare and unnatural carbohydrates as substrates. The mechanism of growth on several of these unnatural carbohydrates has been previously reported. A. aerogenes PRL-R3 possesses the ability to synthesize, in response to the common substrate ribitol, a ribitol dehydrogenase which will also catalyze the oxidation of the rare pentitols xylitol and L-arabitol, but high enzyme concentrations are required before a significant rate of metabolism of these latter two pentitols can occur. Xylitol and L-arabitol are not inducers of the enzyme, and growth with these pentitols as substrates is due to the selection of mutants derepressed for ribitol dehydrogenase (Mortlock, Fossitt, and Wood., Bacteriol. Proc., p. 95, 1964). A mutation for the synthesis of a new or specific pentitol dehydrogenase is not required to permit growth on these unnatural pentitols, even though it is unlikely that the organism has previously encountered these substrates in nature. It has been postulated that growth on the rare aldopentose L-xylose occurs by a similar mechanism with the utilization of D-arabinose isomerase for the isomerization of L-xylOse to L-xylulose (Mortlock et al., Bacteriol. Proc., p. 95, 1964).