BACTERIOLOGICAL TECHNIC 107 



Viscid, growth follows the needle when touched and withdrawn, sediment on shaking 

 rises as a coherent swirl. 



Zooglea, firm gelatinous masses of bacteria, one of the most typical examples of which is 

 the Streptococcus mesenteroides of sugar vats (Leuconostoc mesenterioides), Ihe bac- 

 terial chains being surrounded by an enormously thickened firm covering inside of 

 which there may be one or many groups of the bacteria. 



Notes 



(1) For decimal system of group numbers see Table i. This will be found useful as 

 a quick method of showing close relationships inside the genus, but is not a sufBcient 

 characterization of any organism. 



(2) The morphological characters shall be determined and described from growths 

 obtained upon at least one solid medium (nutrient agar) and in at least one liquid 

 medium (nutrient broth). Growths at 37° C. shall be in general not older than twenty- 

 foiu: to forty-eight hours, and growths at 20° C. not older than forty-eighf to seventy-two 

 hours. To secure uniformity in cultures, in all cases preliminary cultivation shall be 

 practised as described in the revised Report of the Committee on Standard Methods of 

 the Laboratory Section of the American Public Health Association, 1905. 



(3) The observation of cultural and bio-chemical features shall cover a period of at 

 least fifteen days and frequentlylonger, and shall be made according to the revised 

 Standard Methods above referred to. All media shall be made according to the same 

 Standard Methods. 



(4) Gelatin stab cultures shall be held for six weeks to determine liquefaction. 



(s) Ammonia and indol tests shall be made at end of tenth day, nitrate tests at end 

 of fifth day. 



N 



(6) Titrate with — NaOH, using phenolphthalein as an indicator: make titrations at 



same time from blank. The difference gives the amount of acid produced. 



The titrations should be done after boiling to drive of any CO2 present in the culture. 



(7) Generic nomenclature shall begin with the year 1872 (Cohen's first important 

 paper). 



Species nomenclature shall begin with the year 1880 (Koch's discovery of the poured 

 plate method for the separation of organisms). 



(8) Chromogenesis shall be recorded in standard color terms. 



TABLE I 



A Numerical System of Recording the Salient Characters of an Organism 



(Group Number; 



100 Endospores produced. 



200 Endospores not produced. 



10 Aerobic (Strict). 



20 Facultative anaerobic. 



30 Anaerobic (Strict). 



I Gelatin liquefied. 



2 Gelatin not liquefied. 



0.1 Acid and gas from dextrose. 



0.2 Acid without gas from dextrose. 



0.3 .No acid from dextrose. 



