Rogosa, M. (National Institutes of Health, Bethesda, Md.). The genus Veillonella. I. General cultural, ecological, and biochemical considerations. J. Bacteriol. 87:162–170. 1964.—Arguments are presented for excluding Veillonella discoides, V. reniformis, V. orbiculus, and V. vulvovaginitidis from the genus, and for restricting it to aerogenic organisms such as V. parvula and V. alcalescens. The genus Veillonella thus would comprise species which are anaerobic and nonmotile; are small, spherical, gram-negative cocci appearing as pairs, masses, and short chains; and are cytochrome-oxidase- and benzidine-negative. Veillonella would be further characterized in that glucose or any other carbohydrate is not fermented; indole is not produced; gelatin is not liquefied; nitrate is reduced; H2S is produced; propionic and acetic acids, CO2, and H2 are produced from lactate during growth; and pyruvic, oxaloacetic, malic, fumaric, and succinic acids are metabolized by resting cells, but citric, isocitric, and malonic acids are not. In addition to the above, a number of cultural, ecological, and biochemical characteristics are described. At present, V. parvula (the type species) and V. alcalescens would be retained as valid species. Errors in the descriptions of V. parvula and V. alcalescens are corrected by amended statements. These species are differentiated serologically. Also, V. alcalescens differs from V. parvula in having an absolute requirement for putrescine or cadaverine and in decomposing H2O2.