gas (H2 present); some species even attack alginates or pectins. Characteristically, nitrites are produced from nitrates (exceptions in Erwinia) . Antigenic composition is best described as a mosaic which results in serological interrelationships among the several genera, even extending to other families. Many species live in the intestines of man and other ani- mals, frequently causing intestinal disturbances, while others are parasitic on plants, some causing blights and soft rots; still other species are saprophytic, causing decom- position of dead organic materials. Note : Early attempts to develop a satisfactory basis for the recognition of species among the coliform-dysentery-typhoid group of bacteria are reviewed by Winslow, Kligler and Rothberg (Jour. Bact., 4, 1919, 429); these were based largely on differences in motility, production of indole, ability to liquefy gelatin and, more particularly, differences in the ability to ferment carbohydrates, especially such compounds as glucose, lactose, sucrose, dulcitol and salicin. The more recent attempts to express differences in species of coliform bacteria by means of the IMViC reactions are reviewed by Parr (Amer. Jour. Public Health, 26, 1936, 39; also see Bact. Rev., 8, 1939, 1), this cryptic symbol indicating the indole test, methyl-red acid determination, acetj'lmethylcarbinol production (Voges-Proskauer reac- tion) and the utilization of salts of citric acid. Stuart, Griffin and Baker (Jour. Bact., 36, 1938, 391) and Griffin and Stuart (Jour. Bact., 4O, 1940, 83) have applied these tests plus cel- lobiose fermentation to a study of a long series of cultures. Meanwhile, the Kauffmann and White Antigenic Schema has been successfully applied to the recognition of serological groups and types among the organisms placed in the coli- form-dysentery-tj'phoid group. Studies by Kauffmann {Enter ohacteriaceae. Munksgaard, Copenhagen, 1954, 225-254) and Edwards and Ewing (Identification of Enter ohacteriaceae. Burgess Pub. Co., Minneapolis, 1955, 164-176) and others have shown that many cultures previously identified as Aerobacter aerogenes Beijerinck are, culturally and serologically, Klebsiella pneumoniae Trevisan. For this reason it has been recommended by the above- mentioned authors that these two species should be combined as Klebsiella pneumoniae Trevisan, this name having priority over Aerobacter aerogenes Beijerinck. However, because investigators (Kligler, Jour. Inf. Dis., 15, 1914, 187; Stuart, Griffin and Baker, Jour Bact., 38, 1938, 391; Osterman and Rettger, Jour. Bact., 42, 1941, 721; and others) have previously shown that it is diflScult to draw a borderline between the usually non-motile, non-gelatin- liquefjang Aerobacter aerogenes and the usually motile, gelatin-liquefying Aerobacter cloacae Bergey et al., the union of the species Klebsiella pneumoniae and the species Aerobacter aerogenes causes A. aerogenes and A. cloacae to be placed in separate genera. The placing of the latter species in a genus {Cloaca Castellani and Chalmers) is an arrangement that is equally as unsatisfactory as is the present arrangement. While awaiting a better solution of this problem, it has been felt advisable to retain Aerobacter aerogenes as a species distinct from Klebsiella pneumoniae and to retain the genera Aerobacter Beijerinck and Klebsiella Trevisan. From the standpoint of taxonomy, too little attention has been given by the majority of the authors who have proposed adjustments in the classification of the species related to the coliform organisms to the wide distribution and diversity of species that possess character- istics that place them in this group. It has long been known that the coliform organisms that occur in dairy products are frequently derived from grain, and that they occur on the panicles of the grass family in open fields where there is no reason to think that they orig- inated from fecal contamination (Rogers, Clark and Evans, Jour. Inf. Dis., 17, 1915, 137; Rogers, Univ. of Wise. Studies in Science, No. 2, 1918, 104 pp.; Thomas and McQuillin, Proc. Soc. Appl. Bact., 15, 1952, 41; Henriksen, Acta Path, et Microbiol. Scand., 34, 1954, 249- 285 and others). Some of these non-encapsulated organisms, identified as Aerobacter aerogenes Beijerinck, produce a yellow chromogenesis. Although saprophytic coliform or- ganisms from cotton fiber, bagasse (sugar cane fiber), hemp, jute and grain have been recognized as responsible for various types of respiratory diseases in man, it has not been demonstrated how closely these saprophytes are related to Klebsiella pneumoniae. This important problem needs careful review from a variety of viewpoints.
