SECTION B 



Note: Criteria for the separation of the small colorless protozoan forms from 

 bacteria are very limited. Cells in which the chromatinic material is clearly 

 organized into chromosomes which divide and separate during mitosis are 

 probably protozoa. Robinow (Bacteriol. Rev., 20, 1956, 207-242) states that he 

 "knows of no other protists, besides the blue-green algae, with nuclei re- 

 sembling the chromatin bodies of bacteria though it is probable that they 

 exist". The reader is referred to this review for a detailed statement on the 

 position. 



It is suggested that all microbial forms which come under this Section be 

 followed through the key. This practice may assist materially in clarifying the 

 situation. 



1. Ultra-microscopic and filterable forms; strict intracellular parasites of animals and 



plants not cultivable on artificial media but transferable by contact or by arthropod 

 vectors Virales p. 985 



2. Strict parasites occurring within tissue cells of animal hosts or on or in erythrocytes. 



With few exceptions, which have been treated under Section H, they cannot be or 

 have not been cultivated in artificial media. Some can be cultivated in chick embryos 

 or in tissue cultures. In the tissues or blood stream they occur either as spherical ele- 

 mentary bodies and initial bodies from 0.2 to 2.0 microns in diameter or slightly larger 

 (usually 0.20 to 0.35 micron), singly or in aggregations in plaques several microns in 

 diameter or as bacillary, triangular, ring-shaped horseshoe-shaped and other pleo- 

 morphic forms. Bacillary forms may be as long as 3 microns. Stain with Giemsa's or 

 Macchiavello's stain without differentiation into cytoplasmic and nuclear structures, 

 a condition which would be suggestive of protozoa. See Manual keys for the class 

 Microtatobiotes p. 933 



3. Small, spherical bodies, 150 to 300 millimicrons in diameter, which germinate to produce 



filaments approximately 0.2 micron wide and from 2 to 50 microns long, sparcely or 

 richly branching. At a later stage of growth small endomycelial corpuscles develop in 

 the filaments by a process of successive condensation and constriction. As a result the 

 homogeneous filaments are retransformed into chains of close-set spherical bodies 

 which are released by fragmentation; highly resistant to penicillin and sulfathiazole; 

 colonies on agar have a dense granulated central area which penetrates into the agar 

 and which is surrounded by a translucent flat peripheral zone or consist of a pearly 

 film containing numerous spots due to calcium or magnesium soaps; do not ferment 



lactose, sucrose, mannitol or dulcitol Mycoplasma p. 914 



Note: L-phase colonies of some bacteria bear a strong resemblance to the 

 colonies of Mycoplasma. They are generally more opaque, more heavily marked 

 on the surface, tend to revert to the normal bacillary form in penicillin-free 

 semi-solid media, are more difficult to subculture, do not require cholesterol 

 for growth and ferment the same carbohydrates as the parent organism. 



4. Spiral cells ; proceed to Section C p. 998 



This section does not include: (a) all forms like Vitreoscilla, which, through their 

 great length and extreme flexibility, are apt to coil in one plane in watch-spring fash- 

 ion; (b) spiral cells of the streptomyces type which arise from branching Gram-posi- 

 tive filaments; and (c) chains of vibrios. The latter do not possess the true helical 

 twist of the spiral organisms. 



5. Spherical to ovoid cells which reproduce by production of a tubular outgrowth, 0.2 to 



0.3 micron wide, from the cell on the end of which a daughter cell is formed. The 

 tubular outgrowths may be simple or branched. Daughter cells are initially spherical 

 but are later ovoid to rod-shaped; colorless or contain photosynthetic pigments. 



996 



