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SUMMARY Investigations were made of the transformations undergone by the stereoisomers of α,ɛ-diaminopimelic acid in suspensions of acetone-dried organisms of two species of sporulating bacteria, Sporosarcina ureae and Bacillus sphaericus, both of which contain diaminopimelic acid in their spores but not in their vegetative cells. Meso-diaminopimelic acid was rapidly decarboxylated by vegetative organisms of both species; it was also utilized by some other unidentified anaerobic reaction. The vegetative organisms also oxidized meso-diaminopimelic acid with release of ammonia. l-Lysine was oxidized by S. ureae, but not by B. sphaericus. Neither ll-nor dd-diaminopimelic acid was attacked by either organism.
Disintegrated spores of Bacillus sphaericus did not oxidize meso-diaminopimelic acid, but decarboxylated it and also utilized it by the unidentified anaerobic reaction. The decarboxylation, but not the oxidation, of diaminopimelic acid by Sporosarcina ureae was greatly stimulated by pyridoxal phosphate; both reactions were inhibited by the same compounds. Study of the oxidation was complicated by the side reactions which occurred with S. ureae, but a simpler system was provided by an asporogenous variant of B. sphaericus which did not decarboxylate diaminopimelic acid without added pyridoxal phosphate. Only one equivalent of ammonia was produced, a small amount of CO2 was evolved and two equivalents of oxygen were utilized; no oxidation product was identified. The methods of attacking diaminopimelic acid by these two atypical species are compared and discussed in relation to other species in their respective families.