9. Gram-positive 10 Gram-negative 11 10. Organisms occur as cocci under anaerobic conditions in neutral media; in media be- coming acid, they assume a diphtheroid form; extremely pleomorphic under aerobic conditions; produce propionic acid from lactic acid. . . Propionibacterium p. 569 Not as above possibly Mycococcus p. 707 Note: The description of Mycococcus has a strong resemblance to that of Arthrobacter in the earlier literature, and the two generic names may be syno- nj^ms. Micrococcus cinnabareus and M. rhodochrous are included here. 11. Anaerobic; non-motile; Gram -negative; principally rod-shaped cells exhibiting a coc- coid phase; recorded from genital and alimentary tracts of man and other animals Sphaerophorus p. 44^ Aerobic 12 12. Obligate halophiles requiring 16 to 30 per cent salt for growth; not luminescent Halobacterium p. 207 Not obligate halophiles 13 13. Parasites attacking erj'throcj-tes and endothelial cells of man; extremely pleomorphic within the host; straight and curved rods, ring forms and cocci occur; grow in semi- solid rabbit serum agar mainly as rods and cocci ; polar flagella Bartonella p. 969 Note: This genus is selected as an example only of a large group of intracellular parasites which are pleomorphic and have coccal stages. Only an odd species has been cultivated. For other species, see the Manual keys for the class Microtatobiotes p. 933 Animal parasites; non-motile; produce tularemia or tularemia-like infections in ro- dents Pasteurella p. 895 Not as above 14 14. Bioluminescent when grown on fish agar or meat infusion agar containing 3 per cent salt Photobacterium p. 193 Organisms not fitting into anj- of the above groups are probably pleomorphic forms of rod-shaped cells; proceed to Section E p. 1003 15. Organisms parasitic within the cj^oplasm or nucleus of flagellated protozoa 16 Not as above 17 16. Parasitic on the nucleus or nucleolus Caryococcus p. 927 Parasitic in the cj'toplasm of Trichomonas batrachorum Micrococcus p. 929 {M. batrachorum) 17. Strict autotrophs; will not grow on organic media; oxidize ammonia to nitrite or nitrite to nitrate 18 Heterotrophic 19 18. Oxidize ammonia to nitrite; non-motile; not encapsulated . . Nitrosococcus p. 69 Other than above; proceed to Section G p. 1008 19. Obligate anaerobes 20 Aerobic or microaerophilic 23 20. Gram-variable; cells occur singly or in masses; ferment acetate vigorously with the production of methane; discovered in mud Methanococcus p. 473 Not as above 21 21. Gram-positive 22 Gram-negative ; arranged in pairs and clusters ; diameter of cells varies between species from 0.3 to 2.0 microns Veillonella p. 485 22. Organisms arranged in pairs or chains only Peptostreptococcus p. 533 Organisms arranged in cubical packets Sarcina p. 467
