636 CHROMOBACTERIUM 



We append a detailed description of Chr. prodigiosum and Chr. indicum. For 

 a description of other members of this group, see Hefferan (1904). 



Chromobacterium prodigiosum 



Synonyms. — Serratia marcescens Bizio. Micrococcus prodigiosus Cohn. 

 Isolation. — First described by Bizio in 1823 (see Text). 



Habitat. — Water and air ; found on bread, meat, milk, potatoes and other food stuffs. 

 Morphology. — Tiny rods, often oval or cocco-bacillary ; 0-7-1 -0 pi X 0-1 ft ; sides convex, 

 ends rounded, arranged singly and in groups ; irregularity in shape frequent, there 

 being generally some definitely baciUary forms present. Motile by 2-4 peritrichate 

 flageUa. Non-sporing, non-capsulated. Gram-negative, non-acid-fast ; bipolar 

 staining not uncommon. 

 Agar Plate. — 2 days, 25° C. Round colonies, 1-2 mm. in diameter, low convex, smooth, 

 ghstening, paint-like surface, entire edge, amorphous structure ; butjrrous con- 

 sistency, easily emulsifiable. Individual colonies vary from colourless to bright red in 

 colour ; all are translucent. 5 days. Colonies are larger, 2-4 mm. in diameter, 



surface radially striated, edge finely lobate ; differ- 

 entiated into a low convex, red, opaque centre, 

 and an effuse, transparent, colourless periphery. 

 Agar Slope. — Abundant, raised, opaque, scarlet growth, 

 with smooth, paint-like surface and lobate edge. 

 Medium unchanged. 

 Gelatin Stab. — Abundant, fihform growth to bottom of 

 tube. Liquefaction infundibuliform reaching to 

 bottom of tube in 5 days at 20° C. ; liquid is pink 

 at upper part and turbid ; red ring growth at 

 surface ; pink floccular deposit ; rest of growth 



„ ' . uncoloured. 



Fig. 132. — Chromobacterium n ^ x ■ 



prodigiosum. Broth. — 2 days, 25 C. Luxuriant, pmk growth, with 



Surface colony on agar, 24 dense turbidity, a red ring growth, and a moder- 



hours, 37° C. ( X 8). ate, reddish, powdery or finely granular deposit, 



mostly disintegrating on shaking. After 5 days 



there is a red surface pellicle and a heavy fiocculo -granular deposit. Mawkish 



odour, like trimethylamine. 

 Blood Serum. — 7 days, 25° C. Profuse growth ; medium mostly liquefied ; fluid is red 



and turbid. 

 Potato.— Q days at 25° C. Abundant, thick, raised, confluent growth of dark maroon 



colour ; surface papillate and sUghtly ghstening. Potato not coloured. 

 MacConkey Plate. — 24 hours at 37° C. Circular, low convex, opaque, amorphous, pink 



colonies, 1 mm. in diameter, with smooth glistening surface and entire edge. 

 Resistance. — Destroyed by 55° C. for 1 hour. 

 Metabolic. — Aerobe ; slight colourless growth anaerobicaUy. Opt. temp. 25-30° C. 



Grows at 37° C, but no pigment produced. Pigment: blood-red, soluble in chloro- 

 form, not in water. 

 Nutritional. — Grows well on ordinary media. In synthetic media pigment is formed 



only in the presence of MgSOi and a phosphate. 

 Biochemical.— Acid or acid and gas in glucose, maltose, mannitol, sucrose and salicin, 



occasionally in lactose. Indole — . M.R. — . V.P. -|-. Nitrates reduced. NH3 



production-}-. Catalase-f-. M.B. reduction-] — |-. Starch diastase — . HjS -[-. 



L.M. clotted in 2 days, peptonized in 5 days ; fluid pinkish. 

 Pathogenicity. — Non-pathogenic to man ; and to animals except in enormous doses. 



