SECTION C
1. Organisms contain chlorobium chlorophyll or bacteriochlorophyll with carotenoid pigments 2 Organisms do not contain photosynthetic pigments 4 2. Non-motile cells containing only chlorobium chlorophyll; appear distinctly green even under a microscope; may be found in -pure cultures associated with other morpho- logical forms such as rods and streptococcal forms, the latter often predominating; strictly anaerobic cells which oxidize sulfide, depositing sulfur outside the cells Chlorobium p. 62 Note: This pleomorphism, recorded by van Niel, has been disputed by later investigators. Cells contain bacteriochlorophyll and carotenoid pigments; red or purple in masses of cells; actively motile by means of polar flagella 3 3. Organisms grow autotrophically under anaerobic conditions exposed to light; oxidize sulfide and thiosulfate to sulfur, which is deposited inside the cells Thiospirillum p. Jfi Organisms will grow anaerobically when exposed to light but will not grow under strictly autotrophic conditions; require growth factors available in yeast extract; may oxidize sulfide but do not oxidize thiosulfate; sulfur is not deposited in the cells Rhodospirillum p. 58 4. Uniseriate chains of cells enclosed in a sheath; impregnated with iron when in iron- bearing waters; spirally wound around themselves or algal filaments Leptothrix p. 26J^ Note: Species oi Sphaerotilus, considered by Pringsheim and others as identical with Leptothrix, frequently show spirally twisted sheathed forms among nor- mally straight ones. Chains of curved rods wound into a ball within a nearly spherical capsule; do not store iron or manganese Myconostoc p. 260 Spiral cells bearing a torus of iron hydroxide Naumanniella p. 223 Very thin cells wound into tight cylindrical coils 15 to 20 microns long; may be embedded in a capsular material when grown on silica gel. Slowly oxidize ammonia to nitrite Nitrosospira p. 70 Not as above 5 5. Non-motile trichomes spirally wound around each other in bundles; not ensheathed; cells within the trichomes contain gas vacuoles which have a reddish gleam in trans- mitted light Peloploca p. 270 Motile trichomes having a slow, creeping, rotating type of motility on solid surfaces with the tips of the filaments oscillating; no flagella; deposit sulfur internally from sulfide-containing waters Thiospirillopsis p. 840 Not as above 6 6. Cells parasitic on the protozoan Paramecium 7 Not as above 8 7. Cells contain 1.5 to 2.5 spiral turns; tapered at the ends; parasitic within the micro- nucleus of Paramecium aurelia causing marked enlargement of the micronucleus, which is filled with spirals Holospora p. 929 (H. tindulata) Cells incurved in two spiral turns that are not abrupt; one end pointed and the other rounded; no flagella; movement helicoid; endospores are formed; parasitic in the cytoplasm of Paramecium caudatum Drepanospira p. 928
8. Cells, not more than 10 microns long, which may appear spiral in heat-fixed and stained
998
