(2) Actinomyces, generally regarded as anaerobic, is considered by some to be microaerophilic. Organisms growing poorly aerobically but better anaero- bically should be compared carefully with the Actinomyces spp. 12. Organisms which grow over or within submerged plant tissues and on certain labora- tory media, producing conidia within sporangia borne on aerial hyphae 13 Not as above 14 13. Mycelium penetrates the submerged plant tissue; conidia, 1.0 to 1.5 microns in diam- eter, produced in coils or irregularly within the sporangia; conidia globose to slightly angular; sporangia, 8.4 to 22.0 microns in diameter, borne on long aerial hyphae; conidia motile; germinate to produce a branched mycelium Actinoplanes p. 826 Mycelium grows over the surface of submerged plant tissue; conidia spherical, 1.8 to 2.0 microns in diameter, produced in coils within the sporangia; sporangia 7 to 19 microns in diameter produced apically or on branches of aerial hyphae; conidia non-motile and forcibly ejected from a protuberance formed from the sporangium wall when the sporangia are immersed in water Streptosporangiiim p. 828 14. Chains of conidia produced from the ends of aerial hyphae. . . . Streptomyces p. 744 Note: (1) Cultures of Actinoplanes or Streptosporangium on some laboratory media are morphologically similar to Streptomyces. (2) Certain species of Nocardia in which fragmentation is delayed may produce thickened aerial hyphae which abstrict cells from the tip, proceeding towards the base and finally involving the whole mycelium. Early stages in this change may be confused with Streptomyces, e.g., N. fordii and N. paraffinae. Conidia produced singly on the tips of short side branches; branches may occur singly or in clusters giving the appearance of bunches of grapes 15 Mycelium persistent with no production of conidia. These forms should be regarded in the same sense as the Mycelia sterilia of the Fungi until something more definite is known of possible fruiting structures. 15. Do not grow between 50° and 60°C Micromonospora p. 822 Growth occurs between 50° and 60°C.; aerial mycelium produced Thernioactinomyces p. 824 16. Acid-fast Mycobacterium p. 695 Non-acid-fast 17 17. Rudimentary branching rods only under aerobic conditions or in acid media anaerobi- cally; produce chains of cocci or short rods in neutral media under anaerobic condi- tions; propionic acid produced from lactic acid Propionibacterium p. 569 Cells have a definite cyclic development; spherical cells germinate at one or more points to produce rod-shaped cells which elongate and divide. At the point of divi- sion, growth of the cells continues at an angle to the original axis. When side branches are equal in size to the parent cell, division occurs at the angle. This process is re- peated during the growth of the colony. In older colonies the rods transform entirely into a 7nass of cocci. Rods are most frequently Gram-negative with Gram-positive granules; the coccal forms are frequently Gram-positive. Recorded mainly from soils Arthrobacter p. 605 Note: The emphasis lies on the final transformation into cocci. Some authorities may consider that limited true branching may occur. If this is admitted, the dividing line between Arthrobacter and Nocardia becomes very slim. The au- thor's observations of Arthrobacter globiforme fit the above statement, and it is suggested that these criteria be adopted, true branching forms which later disintegrate being assigned to Nocardia. Organisms produce both coccoid and rod-shaped forms, the latter frequently branch- ing. Coccoid resting cells are produced which may germinate at one or more points. The coccoid forms generally predominate Mycococcus p. 707
