cc. Ferment glucose anaerobically, frequently producing visible gas (CO2 + H2) from glucose and sometimes lactose. Reduce nitrates (rare exceptions). Frequently found in the alimentary, respiratory and urinary tracts of vertebrates, others are free-living, while still others are plant pathogens. Famil}^ IV. Enterobacteriaceae, p. 332. bb. Usuallj^ small, motile or non-motile rods. Obligate animal parasites which usually require body fluids for growth. Man}' fail to grow on ordinar}^ media. The majority do not ferment glucose anaerobically. Family V. Brucellaceae , p. 394. B. Anaerobic to microaerophilic, rod-shaped organisms which sometimes show branch- ing. Family VI. Bacteroidaceae, p. 423. II. Cells spherical to rod-shaped. Usually Gram-positive, though some cocci and anaerobic spore-forming rods lose the Gram stain readil3^ A. Cells do not form endospores. 1. Cells spherical, occurring in masses, tetrads or packets of eight cells. a. Spherical cells. Gram-positive. Aerobic or anaerobic. Family VII. Micrococcaceae, p. 454. aa. Cells spherical. Gram-negative. Aerobic or anaerobic. Frequently occur in pairs. Family VIII. Neisseriaceae, p. 480. 2. Cells either spherical, occurring in chains, or rod-shaped. Gram-positive, but cells may lose the Gram stain readily in old cultures. a. Cells rod-shaped, no pleomorphism or branching of cells. Rarely or never ferment glucose anaerobically. Family IX. Brevibacteriaceae, p. 490. aa. Not as above. b. Gram-positive cocci and rods which frequentl}' form chains of cells. Cells ferment sugars anaerobically with the production of lactic, acetic, propionic, butyric, etc. acids. Microaerophilic to anaerobic, c. Homo- and hetero-fermentative cocci and rods whose chief product in fermentation is lactic acid. Do not reduce nitrates. Family X. LactobaciUaceae, p. 505. cc. Rod-shaped bacteria whose distinctive product in fermentation is propionic acid, butyric acid or ethanol. All produce CO2 . Family XI. Propionibacteriaceae, p. 569. bb. Cells generally rod-shaped but wedge and club forms are common. The cells are usually found in angular or picket formations due to snapping division. Old cells are frequently Gram-negative. Not active in the an- aerobic fermentation of sugars. May or may not reduce nitrates. Family XII. Corynebacieriaceae, p. 578. B. Rod-shaped cells that produce endospores. Aerobic and anaerobic. Some anaerobic species lose the Gram stain readily. Family XIII. Bacillaceae, p. 613.
