GROWTH REQUIREMENTS 



615 



very actively motile by a single polar flagellum. They stain best with dilute 

 carbol-fuchsin. They are Gram-negative. 



Growth Requirements. — Growth occurs readily on the usual media. One of 

 the most characteristic properties is the rapidity of growth in peptone water (1 per 

 cent, peptone, 0-5 per cent. NaCl). 



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Fig. 101. — Vibrio cholerce. 

 From an agar culture, 24 hours, 37° C. (X 1000). 



Multiplication occurs chiefly at the 

 surface, where, after 6 to 9 hours, 

 a delicate membrane is formed. 

 There is very little turbidity as a 

 rule ; the deposit that forms ap- 

 pears to be derived from the 

 surface pellicle. 



The vibrios are markedly aero- 

 bic ; they grow best in the pre- 

 sence of abundant oxygen. Under 

 strictly anaerobic conditions some 

 of the members fail to grow alto- 

 gether ; the majority give rise to 

 a very slight growth on agar or in 

 broth in about a week. The opti- 

 mum temperature is 30—40° C. ; 

 no growth occurs macroscopically 

 under 16° C. 



For growth and survival a 

 H-ion concentration of pH 7-6-8-0 is most suitable. The organisms have a high 

 alkali, but a very low acid tolerance. Cultures containing a fermentable sugar 

 are sterile in a day or two (Nobechi 1925). 



A number of selective media have been devised for facilitating the isolation of 



V . cholerce from the faeces. 



One of the best known of these — Dieudonne's 

 medium (1909) — is prepared by addmg normal KOH 

 solution to an equal quantity of defibrinated ox blood, 

 and heating to 100° C. for half an hour. Thirty parts 

 of this mixture are added to 70 parts of nutrient agar 

 rendered neutral to htmus. According to Vedder and 

 van Dam (1932), the medium should be allowed a day 

 or two to " ripen." During this time COj is taken 

 up from the air and NH3 is given off. The medium, 

 when ready for use, should have a pH of 90-9-6. 

 At a lower pH coliform and other organisms grow and 

 the medium is no longer selective ; at a higher pH the 

 growth of the cholera vibrio itself is inhibited. Otto- 

 lenghi's medium (see Bocchia 1911) consists of ox bile 

 to which 3 per cent, of a 10 per cent, solution of 

 crystaUuie sodium carbonate has been added ; steri- 

 Uzation is effected in the autoclave. Bandi's medium, suitable for cultivation of the 

 cholera vibrio from water, is a peptone water solution containing dilute anticholera agglu- 

 tinating serum ; the vibrios multiply and fall to the bottom in clumps. Yen (1932-33) 

 recommends a phenolphthalein starch medium for the isolation of the cholera vibrio. 

 It depends on the unusual property possessed by this organism of rapidly fermenting 

 starch in an alkaline solution (see Gordon 1906). 



Fig. 102. — Vibrio cholerce. 



Surface colonies on agar, 24 hours, 

 37° C. (X 8). 



