FAMILY XI. PROPIONIBACTERIACEAE DELWICHE, Fam. Nov.* Pro.pi.on.i.bac.te.ri.a'ce.ae. M.L. neut.n. Propionihacterium the type genus of the family; -aceae ending to denote a family; M.L. fem.pl.n. Propionibacteriaceae the Propioni- bacterium family. Irregularly shaped rods which tend toward bending or terminal swelling (in Butyribac- ferium) or pleomorphism (in Propionibacterium) . Non-motile. Gram-positive. Colonial de- velopment on semi-solid media is slow, visible colonies seldom being discernible before two days. Where pigment is produced, it is brownish red. Non-proteolytic; usually saccharolytic. Ferment carbohydrates, usually lactic acid and, in some cases, polj'hydroxy alcohols with the production of saturated aliphatic carboxylic acids. With Propionibacterium, extensive carbon dioxide production occurs with some substrates. Lactic acid usually does not ac- cumulate. Anaerobic to aerotolerant, many strains of Propionibacterium being readily adapted to growth under aerobic conditions, with the actual utilization of oxygen. Gener- ally catalase-positive when subjected to the usual laboratory test, but exceptions exist, particularly in Butyribacterium. Inhabitants of the intestinal tracts of animals; also occur in materials outside the body where suitable foodstuffs are found. Key to the genera of family Propionibacteriaceae, I. Ferment carbohydrates and lactic acid. A. Produce propionic and acetic acids and carbon dioxide. Genus I. Propionibacterium, p. 569. B. Produce butj'ric and acetic acids and carbon dioxide. Genus II. Butyribacterium, p. 577. II. Carbohj^drates are fermented. Glucose is converted mainly to ethanol and carbon diox- ide, with small amounts of acetic and other acids. Lactic acid is not fermented. Genus III. Zymobacterium, p. 577. Genus I. Propionibacterium Orla-Jensen, 1909.' (Cent. f. Bakt., II Abt., 2£, 1909, 337.) Pro.pi.on.i.bac.te'ri.um. Gr. pref. pro- before, priority in order; Gr. neut.n. pium (pion) fat; ]M.L. adj. propionicus propionic, referring to priority in the fatty acid series of com- pounds as in acidum propionicum propionic acid; Gr. dim. noun bacterium a small rod; M.L. neut.n. Propionibacterium propionic bacterium. Non-motile, non-sporeforming, Gram-positive bacteria which grow under anaerobic con- ditions in neutral media as short, diphtheroid rods which sometimes resemble streptococci in appearance; under aerobic conditions and with a heavy inoculum, thej^ grow as long, ir- regular, club-shaped and branched cells. Metachromatic granules are demonstrable with Albert's stain. Ferment lactic acid, carbohj'drates and polyhydroxy alcohols with the pro- duction of propionic and acetic acids and carbon dioxide. As a rule, strongly catalase-posi- tive, sometimes weakly so. There is a strong tendency towards anaerobiosis; development is slow, macroscopically visible colonies generally not discernible in less than five to seven days. J Nutritional requirements complex. Development best in yeast extract media with the addition of lactates or simple carbohydrates. Vitamin B requirements are relativelj'
- Proposed by Prof. E. A. Delwiche, Cornell University, Ithaca, New York, November,
1954. t Revised by Prof. C. B. van Niel, Hopkins Marine Station, Pacific Grove, California, Januar}^ 1944. % In an atmosphere containing 5 per cent carbon dioxide, growth is enhanced both aerobi- cally and anaerobically. Contrary to the claim made by Krebs and Eggleston (Biochem. Jour., 35, 1941, 676), a differential effect of carbon dioxide tension on aerobic and anaerobic development has never been observed.
