Species metabolic patterns in morphologically similar gram negative pathogens.

The morphological, cultural, biochemical, an(l nutritional characteristics of many of the species of microorganisms that are classified within the genera of Moraxella, Neisseria, Brucella, and Bordetella are so similar that identification of small gram negative organisms is both tedious and difficult. This impressive similarity that exists between species, and even between genera, is probably indicative of a close biological relationship, but it has created taxonomic problems. Henricksen (1952) discusses the lack of distinguishing characteristics between Moraxella and ANeisseria, and suggests that the two genera may be closely related. There is, in fact, no cultural or biochemical feature that clearly delineates these two genera. When Bergey's Manual (Breed et al., 1948) created the genus Moraxella, it was placed in the tribe Haemophileae. Its relationship to other genera in this tribe, particularly IIaemophilus, has not been clearly established. Proom (1955), on the basis of nutritional evidence, supported the proposal of M\orenoL6pes that Brucella bronchisepticus, Haemophilus pertussis, and Haemophilus parapertussis be classified into the genus Bordetella. In view of the fact that this newest classification of these species will appear in the forthcoming seventh edition of Bergey's Manual, that nomenclature will be followed in this paper. Many of the difficulties attendant upon identifying and classifying the small gram negative pathogens seemingly arise from a lack of information concerning the general metabolism of each species. The physiological studies reported herein were undertaken to determine if the basic metabolic pattern of selected species within the genera of Brucella, Moraxella, Neisseria, and Bordetella, that are culturally difficult to differentiate one from the other, would display enough characteristic metabolic differences to aid in identifying the species, and to perhaps help determine their taxonomic relationships. MATERIALS AND METHODS